Particle-Astro-Nuclear (PAN) Physics seminars

This seminar series presents research covering topics high energy physics, quantum field theory, astroparticle, particle, and nuclear and hadronic physics.

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Winter 2024
May 14, 2024

Randa Asad, American University of Sharjah

Ages, metalicities and detailed abundances of star clusters from their resolved and unresolved spect

Abstract

I will present the different techniques our group used to obtain the age, metallicity and detailed abundances of star clusters in the Milky Way and the Magellanic Cloud. The first part of my talk will focus on using XShooter/VLT IR spectra of RSG to obtain the metallicity of newly discovered young star clusters in the inner Milky Way. The second part will discuss the first detailed chemical abundances of three star clusters in the Large Magellanic Cloud (LMC), NGC1831 , NGC1856 and [SL63]268 using integrated-light spectroscopic observations obtained with the Magellan Echelle spectrograph on Magellan Baade telescope. And finally I will present the first application of the novel approach based on data-driven machine learning methods applied to MUSE field data to derive stellar abundances of star clusters. MUSE has been used to target more than 10,000 fields, and it is unique in its ability to study dense stellar fields such as stellar clusters providing spectra for each individual star. The revolutionary combination of integral-field spectroscopy and data-driven modeling will allow us to understand the chemical enrichment of star clusters and their host galaxies in greater detail expanding our understanding of galaxy evolution.

April 19, 2024

Joshua Spitz, University of Michigan

Using Ancient Rocks to Look for Atmospheric Neutrinos

Abstract

Earth is constantly being bombarded by cosmic rays, energetic particles from the cosmos. These particles provide a window on both the nature of their astrophysical sources and into multiple aspects of particle physics and cosmology. Recently, it has been pointed out that the history of the cosmic ray rate over the past ∼1 billion years can be measured using atmospheric neutrino (produced readily in cosmic ray interactions with the Earth’s atmosphere) induced imprints in minerals, or “paleo-detectors”, buried deep beneath the Earth’s surface. The time evolution of cosmic rays provides a unique window into the history of the Earth, including aspects of the geo- and helio-magnetic fields, the atmosphere, and the trajectory of our planet through the Milky Way galaxy, noting that the Earth goes around the galaxy once every 230 million years. In this talk, I will discuss the overarching paleo-detector concept in the context of a number of physics studies, and our group's pursuit of measuring atmospheric neutrinos in these ancient rocks.

April 12, 2024

Junjie Zhu, University of Michigan

Latest diboson polarization results from ATLAS

Abstract

In the Standard Model of particle physics, the Higgs field plays a crucial role by spontaneously breaking the underlying electroweak symmetry. This process gives rise to a massive Higgs boson and three massless Goldstone bosons. The massless Goldstone bosons are then absorbed into the W and Z bosons, transforming them into their longitudinal components and giving them mass. It is thus interesting to study longitudinal polarizations of W and Z bosons. In this presentation, I will discuss the latest diboson polarization studies conducted at ATLAS with WZ and ZZ diboson events, and I will focus on new results on diboson polarization fraction measurements at high energies as well as the first observation of radiation amplitude zero effects using WZ events.

April 5, 2024

Jonathon Crass, Ohio State University

iLocater: Searching for Earth-like exoplanets among the stellar noise

Abstract

Highlighted as a strategic goal in the “Worlds and Suns in Context” science theme of the 2021 “Pathways to Discovery”Decadal Survey Report, the detailed characterization of rocky exoplanet systems requires extreme precision radial velocity (EPRV) measurements to provide mass, bulk composition, and orbital information. Such high-resolution spectroscopic capabilities help assess the potential for habitability, support studies of planet formation, and maximize the scientific return of broader exoplanet missions. With such strong scientific motivation, advancing EPRV spectrographs to the centimeter-per-second level is important need, however, reaching such a goal is complex; the performance of current instruments is no longer solely dominated by systematic effects, but also by host-star stellar variability which can have an order of magnitude larger RV signature than rocky-planets.

iLocater is a new type of EPRV instrument under development for the dual 8.4m diameter Large Binocular Telescope (LBT) which aims to address this challenge. The instrument uses adaptive optics (AO) to efficiently inject diffraction-limited starlight into single-mode fibers (SMFs) at near-infrared wavelengths and is optimized for precision studies of late-type stars. Operating at the diffraction limit offers a multitude of advantages for generating precise Doppler time series measurements, specifically enabling high spectral resolution (R>150,000) EPRV capabilities on a large ground-based telescope. Such resolutions are critical in disentangling stellar effects from planetary signatures.

I will present an overview of iLocater including its design, status, expected performance and unique scienceprograms. In addition, I will describe how iLocater fits into the broader EPRV landscape, future directions for the program, and broader SMF instrument development.

March 29, 2024

Filomena Nunes, Michigan State University

BAR: Bayesian Analyses of Reactions

Abstract

Nuclear reactions are an essential probe for studying isotope structure and nuclear astrophysics. It is from nuclear reactions that we learn about where nuclei come from and how they are produced. Also, reaction experiments provide critical knowledge on how neutrons and protons organize themselves to form matter as we know it and matter at the limits of stability.

However until recently, models for nuclear reactions included no uncertainty quantification. In this presentation, I will review the Bayesian analysis efforts developed over the last 6 years in reaction theory, including not only uncertainty quantification but also steps toward experimental design. This presentation assumes no prior knowledge on Bayesian Statistics.

Some relevant references:
[1] C. Hebborn et al., J. Phys. G 50, 050601 (arXiv:2210.07293)

[2] G.B. King et al., Phys. Rev. Lett. 122, 232502 (2019)

[3] A. Lovell et al., J. Phys. G 48, 014001 (2020)

[4] M. Catacora-Rios et al., Phys. Rev. C 100, 064615 (2019)

[5] T. Whitehead et al., Phys. Rev. C 105, 054611 (2022)

[6] M. Catacora-Rios et al., Phys. Rev. C 108, 024601 (2023) (arXiv:2212.10698)

[7] M. Catacora-Rios et al., Phys. Rev. C 104, 064611 (2021)

March 22, 2024

Mesut Arslandok, Yale University

Unveiling hadronization processes new insights and future perspectives with ALICE at LHC

Abstract

The theory of strong interaction, QCD, suggests that at high energy densities, nuclear matter transitions into a state known as the quark-gluon plasma (QGP), in which quarks and gluons move freely. Ultrarelativistic heavy-ion collisions provide an ideal environment to study this phase transition and explore the process of hadronization as the hot QCD medium formed gradually cools down. In this talk, I will give an overview of the latest findings of the ALICE collaboration on the hadronization process, focusing on correlation functions and multiplicity fluctuations in view of different hadronization models such as string fragmentation, coalescence and statistical hadronization. I will also discuss future prospects for exploring the QCD phase diagram, particularly in light of the planned ALICE3 detector planned for the early 2030s. Towards the conclusion, I will introduce an innovative program aimed at searching for new physics beyond the Standard Model utilizing the ALICE TPC.

March 8, 2024

Angelo Ricarte, Harvard University

Event Horizon Insights Into the Cosmic Assembly of Supermassive Black Holes

Abstract

The past few years have featured major advances in supermassive black hole astrophysics: from the gravitational wave background, to measurements at cosmic dawn, to the first spatially resolved images. These observations, in tandem with theoretical advances on both event horizon and galactic scales, have spurred progress on longstanding problems in black hole seeding, accretion, feedback, and dynamics. I will first explain how we image black holes with the Event Horizon Telescope, a worldwide network of millimeter observatories, and how these images favor models with saturated magnetic fields. I will then introduce Serotina, a flexible semi-analytic modeling framework for the black hole-galaxy co-evolution on cosmological timescales. I will use this cosmological framework to self-consistently predict multi-messenger observables including spin distributions, high-redshift luminosity functions, and gravitational waves. We will explore the cosmological implications of magnetically saturated accretion disks and compute observational signatures in black hole populations. As new types of observations become available in the next decade, this multi-scale theoretical approach will enable us to construct a holistic picture of supermassive black hole evolution over cosmic time.

March 1, 2024

Malu Sudha, Wayne State

A Broadband Spectro-Temporal View of NS LMXBs

Abstract

Neutron Star (NS) Low Mass X-Ray Binaries (LMXBs) are phenomenologically rich systems that consist of a neutron star accreting matter from a low mass (< 1 M_⊙) companion star. NS LMXBs that trace out a characteristic Z-shaped track in their hardness-intensity diagram (HID) or in their color-color diagram (CCD) are classified as ‘Z’ sources and those that trace out a characteristic C shaped track in the HID are classified as ‘atoll’ sources. The current picture of these binaries involves an accretion disk formed via Roche lobe overflow from the secondary star, a boundary layer around the NS surface (which is the site where the disk material reaches the relatively slowly spinning NS), a compact corona/hot electron cloud close to the NS. But the exact location, structural configuration in this region or the extent of the corona and its nature is not clearly understood. Timing variability in NS LMXBs can vary from a timescale of a few seconds to a few years. These systems exhibit a multicolor disk blackbody emission from the accretion disk, a hot blackbody emission from the boundary layer, a hot Comptonized emission from the corona and a reprocessed emission from the innermost accretion disk region. Although several models have been proposed to explain the spectral and temporal nature of these binaries, a unified model that addresses the spectral and temporal nature of these systems is essential. In this talk I will be discussing the broadband spectro-temporal studies of these NS LMXBs. Results obtained from these studies will be discussed in the context of understanding the physical behavior and geometry of the inner accretion disk region of NS LMXBs.

February 23, 2024

Alakadha Datta, University of Mississippi

A sterile neutrino behind the B and MiniBooNE anomalies

Abstract

Recent evidence of the decay B→K+inv by Belle II show around a 2.7 sigma deviation from the standard model prediction. This measurement is explained with a dark scalar, S, that couples to the standard model particles and a massive sterile neutrino, N, which mixes with the active neutrinos. The flavor changing neutral current process B→KS→Kνbar{nu} then explains the Belle II measurement. The same set up can also explain the excess in electron like events observed in the MiniBooNE experiment and the muon g-2. I will discuss how the massive sterile neutrino can be probed in charged current B decays such as B→D^* l N at Belle II and at the FASER experiment.

February 16, 2024

Friederike Bock, Oak Ridge

A New Era of Electron-Ion Collider Physics - The ePIC detector and its forward calorimeter

Abstract

The Electron Ion Collider (EIC) is the next Nuclear Physics flagship experiment to be constructed at Brookhaven National Lab over the next decade. The ePIC detector will be the first experiment at the EIC dedicated to detailed studies of nuclear structure in electron-proton and electron-ion collisions. The ambitious physics program of the EIC requires a high performance hadronic calorimetry system in the hadron-going "forward" region. Accurate jet measurements are crucial to reconstruct the full 3D nucleon tomography and to study the gluon saturation region. The main goal of the Longitudinally segmented Forward HCal (LFHCAL) is measuring the energies of jets and distinguishing between overlapping jet depositions to high accuracy in the jet energy range up to 120 GeV. LFHCal is designed as a plastic scintillator-steel sandwich calorimeter. The plastic scintillator is transversely segmented into 5x5 cm2 tiles. Each tile is directly coupled to a silicon photomultiplier. The electrical signals of all photomultipliers are routed out of the LFHCAL to be digitized by external readout electronics based on the H2GCROC3 developed for the CMS HGCAL project.

This talk will present a general introduction to EIC physics as well as the ePIC detector concept. Particular emphasis will be put on the current status of the LFHCAL for the ePIC experiment. This will include results from SiPM characterization measurements and scintillator light yield comparisons from lab measurements as well as initial results from a first small-scale test beam prototype operated at CERN PS and SPS in the fall 2023.

February 9, 2024

Zhong Yang, CCNU

Quark-gluon plasma and jet-induced medium response in high-energy heavy-ion collisions

Abstract

The jets are powerful probes of quark-gluon plasma (QGP). When a jet loses energy to the QGP medium, it induces the medium response resembling a Mach-cone-like excitation. Investigating this jet-induced medium response can help us to understand QGP properties. We have developed a 2D jet tomography method to localize the initial jet positions and enhance the signal of the jet-induced diffusion wake—an unambiguous part of the medium response. Additionally, we employ a neural network to assist this tomography. To further study the jet-induced diffusion wake, we carry out the simulation of its 3D structure, and investigate its sensitivity to QGP medium properties. We also show that one can use the energy-energy correlators, a novel jet substructure observable, to investigate jet-induced medium response and the short distance structure of QGP in heavy-ion collisions.

February 2, 2024

Labani Mallick, University of Manitoba and CITA, University of Toronto

Impact of AGN on Black Hole’s Event Horizon, Host Galaxy, and Beyond

Abstract

Astrophysical black holes are surprisingly simple physical objects. Their gravitational field can be fully described by two parameters: mass and spin. We cannot directly observe black holes as no light escapes from the event horizon. However, we can detect the light from accreting gas, which forms a dense disk around the black hole, known as an accretion disk. The accretion of material by a massive black hole at the center of its host galaxy forms an active galactic nucleus (AGN), the innermost region of which emits X-ray radiation. An AGN is energetically efficient for regulating the growth of galaxies and is crucial for the development of the Universe we see today. One of the most important tools to probe the innermost accretion flow is the detection of X-ray reverberation echoes, where the X-ray photons reflected from the accretion disk are delayed relative to the primary X-ray source. In this talk, I will first discuss how detailed measurements of the reflected X-rays from the accretion disk can be used to probe the innermost regions of accretion flow just outside the event horizon and determine the fundamental properties of the black hole, such as its spin, across the complete mass scales from around ∼ 10^5 − 10^10 solar masses. Peering into the growth channels of black holes, I will discuss how we can distinguish accretion vs. merger-dominated black hole growth and probe the cosmological evolution of black hole spins in the last 10 billion years of cosmic history. Finally, I will show how enigmatic relativistic winds or Ultra-Fast Outflows (UFOs) launched from the AGN accretion disk can be used to probe the feedback mechanism connecting the central black holes with their host galaxies.

January 26, 2024

Sandeep Chatterjee, IISER Berhampur

Deposition and evolution of baryons in relativistic heavy ion collisions

Abstract

Relativistic heavy ion collisions provide us a rare opportunity to study the QCD phase diagram. This necessitates the understanding of the deposition and transportation of the baryon conserved charge in these collisions. I will present our recent phenomenological studies within the framework of relativistic hydrodynamics in this direction. I will further elucidate how several observables based on electric charge splitting that have been proposed and measured as signals of the initial large electromagnetic field in these collisions receive strong background contributions from the physics of baryon stopping, leaving open their interpretation.

January 19, 2024

Hendrik Roch, Wayne State University

Hybrid Hadronization and Fragmentation Hadrons in the Afterburner within the JETSCAPE Framework

Abstract

In this seminar, I will introduce the latest developments in the JETSCAPE 3.6 framework, focusing on enhancements in the hybrid hadronization module. The talk delves into the benefits of hybrid hadronization, presenting a unified hadronization framework applicable to diverse partonic systems—ranging from $e^++e^-$ and $p+p$ collisions to full heavy-ion collisions, encompassing a bulk medium. With the updated JETSCAPE framework, we gain the capability to incorporate hadrons generated from hard processes into a subsequent hadronic afterburner phase (SMASH). The investigation explores the impact of hadronic rescatterings on various event shape, jet observables, and particle spectra. Preliminary results will be presented, highlighting intriguing effects even in $e^++e^-$ systems.
Fall 2023
December 8, 2023

Cliff Burgess, McMaster University, Hamilton, ON

Open EFTs: A Decoherent Description of Primordial Fluctuations (special time)

Abstract

Precision calculations in cosmology (such as of inflationary predictions for primordial fluctuations) are often plagued by infrared problems and issues of secular time dependence. These usually signal the breakdown of perturbative methods at late times. Similar issues about how to make controlled predictions at late times seem also to arise for information loss in black holes. This talk briefly summarizes how related problems arise in other areas of physics, and how they are dealt with when they do. It is argued that Master-Equation/Lindblad techniques used in areas like optics also apply to cosmology (and possibly black holes) and can tell us how to extract reliably late-time predictions. The utility of these tools is illustrated by using them to predict how quickly primordial quantum fluctuations decohere after their production during inflation and their later emergence as the classical fluctuations observed to seed structure formation in the later Big Bang Epoch.

December 1, 2023

Gregoire Pihan , Wayne State University, Detroit, MI

Tracing the baryon number in relativistic isobar collisions at RHIC

Abstract

Traditionally, the baryon number and electric charge within a proton are attributed to the valence quarks. However, a novel conceptualization known as the "baryon junction" challenges this paradigm by proposing that the baryon charge is associated with a Y-shaped, non-perturbative gluonic configuration inside hadrons. Recent preliminary analyses of isobar collisions at the Relativistic Heavy Ion Collider (RHIC) reveal that the scaled net-baryon to net-electric charge number ratio at midrapidity ($B/Delta Q * Delta Z/A$) falls within the range of 1.5 to 2. This aligns with predictions derived from the baryon junction model, marking a significant development. This outcome strongly suggests that, in high-energy collisions, the carrier of the baryon number is the baryon junction rather than the valence quarks. However, it is important to note that existing predictions pertain solely to the initial collision stage.

In this study, we establish a comprehensive (3+1)D relativistic hydrodynamic framework incorporating multiple conserved charge currents to systematically investigate this measurement from the initial to the final stage. Simulating the coupled propagation of net baryon and electric charge currents and incorporating a charge-dependent lattice-QCD-based equation of state, we explore the evolution of these charges throughout various phases of heavy-ion collisions. Our findings demonstrate that the aforementioned ratio, as measured in Ru+Ru and Zr+Zr collisions at $sqrt{s_mathrm{NN}}=200$ GeV, persists until the final stage, providing quantitative agreement with STAR preliminary measurements.

November 17, 2023

Christopher Madrid, FNAL

Harnessing Time: The CMS MIP Timing Detector for the HL-LHC Era

Abstract

As the High-Luminosity LHC (HL-LHC) era approaches, the Compact Muon Solenoid (CMS) experiment at CERN has embarked on a significant upgrade with the introduction of the MIP Timing Detector (MTD). Designed to combat the anticipated high levels of pile-up, the MTD promises to measure the time-of-arrival of minimum ionizing particles with a sharp resolution of 30-40 ps. It is an exciting venture aimed at preserving the renowned particle identification and reconstruction capabilities of CMS. Central to the MTD's structure are the Endcap Timing Layer (ETL) utilizing low-gain avalanche diode (LGAD) sensors, and the Barrel Timing Layer (BTL) that integrates LYSO:Ce crystals with SiPMs. The incorporation of timing data into CMS will rejuvenate event reconstruction quality, even with closely spaced vertices. In this presentation, we will delve into the MTD's design, share the latest on prototyping and test beam results, and highlight its potential impact on CMS's performance at the HL-LHC.

November 3, 2023

Yang-Ting Chien, Georgia State University, Atlanta, GA

Open Target jet substructure and correlation

Abstract

I will discuss the reconstruction of target jet and the framework of quantifying its internal substructure. Due to momentum and charge conservation, target and current correlation can be exploited which significantly constrains the event-wide particle distributions. I will demonstrate this method using Pythia simulations of electron-proton collisions in the context of determining the flavor and substructure of the struck quark jet. Extensions to electron-ion collisions and target tagging using BeAGLE simulations will be discussed. Hopefully this study will be useful for forward detector designs and the synergy with nuclear physics.

October 27, 2023

Andrew Olivier, University of Norte Dame, Norte Dame, IN

Neutron Detection at the MINERvA Neutrino Scattering Experiment

Abstract

Neutrino oscillations are the key to unlocking two of the final puzzles of the Standard Model: neutrino masses and CP violation in the lepton sector. Accelerator-based oscillation experiments with O(1 GeV) neutrinos are a promising method to measure these properties. GeV-scale charged leptons from these neutrinos are easy to measure, but the hadrons they produce are not. Interactions inside the target nucleus make O(100 MeV) changes to the hadrons detected, and neutrons invisibly carry energy away from the interaction. The MINERvA neutrino scattering experiment has helped constrain nuclear effects in neutrino scattering since 2009. New sensivity to neutrons at MINERvA presents an opportunity for novel cross section measurements. The MINERvA collaboration recently used neutron direction reconstruction to isolate the cross section for antineutrino interactions on a free proton. Our latest result, the multi-neutron production cross section, opens new windows for understanding nuclear effects.

October 20, 2023

Ouynh Lan Nguyen, University of Norte Dame, Norte Dame, IN

Dark Matter, Neutron Star, and Gravitational Waves

Abstract

The small scale structure problems remains a challenging discrepancy between observations and simulations in the standard LambdaCDM model for the formation of galaxies. The problem is that LambdaCDM simulations predict a steep power-law mass density profile at the center of galactic dark matter halos. However, observations of dwarf galaxies in the Local Group reveal a density profile consistent with a nearly flat distribution of dark matter near the center. A number of solutions to this dilemma have been proposed. Here, we summarize investigations into the possibility that the dark matter particles themselves self interact and scatter. Such self-interacting dark matter particles can smooth out the dark-matter profile in high-density regions. In this talk, we will present the beyond standard model for MeV dark matter and its constraint with the astrophysical observations. We also study the formation of the halo dark matter and its impact on properties of neutron stars included mass, gravitational mass, and tidal deformability.

October 13, 2023

Anne Medling, University of Toledo, Toledon, OH

Observational Constraints for Physical Models of Black Hole Fueling and Feedback

Abstract

I will review the important component parts of black hole fueling and feedback models and discuss observational constraints recently or newly available to test our inputs to hydrodynamical simulations. Among them, I will present KOALA: the Keck OSIRIS AO LIRG Analysis, an adaptive optics-assisted near-infrared integral field spectroscopy campaign of 30+ nearby gas-rich galaxy merger nuclei. Our dataset traces stellar and gas kinematics and properties at few 10s of pc resolution, providing an excellent laboratory for studying the fueling and feedback associated with the central supermassive black holes and nuclear starbursts. These data have shown that 50-500 pc nuclear disks are a nearly ubiquitous mechanism for funneling gas to the black holes. High central dynamical masses suggest that black holes may 'claim their mass' early in a merger, but that that material takes much of the merger timescale to find its way through the accretion process. This gas pileup scenario is supported by recent ultra-longbaseline ALMA observations and presents a significant challenge to current common sub-grid black hole accretion rate prescriptions. Our dataset also reveals high ratios of shock-excited molecular gas (H_2 2.12 micron emission) compared to ionized hydrogen (Br gamma emission) reveal star formation- and AGN-driven nuclear outflows that in some cases can be traced out to several kpc scales. For more information on the survey and access to our data, visit koala-goals.github.io.

September 22, 2023

Ouynh Lan Nguyen, University of Norte Dame, Norte Dame, IN

Dark Matter, Neutron Star, and Gravitational Waves

Abstract

The small scale structure problems remains a challenging discrepancy between observations and simulations in the standard LambdaCDM model for the formation of galaxies. The problem is that LambdaCDM simulations predict a steep power-law mass density profile at the center of galactic dark matter halos. However, observations of dwarf galaxies in the Local Group reveal a density profile consistent with a nearly flat distribution of dark matter near the center. A number of solutions to this dilemma have been proposed. Here, we summarize investigations into the possibility that the dark matter particles themselves self interact and scatter. Such self-interacting dark matter particles can smooth out the dark-matter profile in high-density regions. In this talk, we will present the beyond standard model for MeV dark matter and its constraint with the astrophysical observations. We also study the formation of the halo dark matter and its impact on properties of neutron stars included mass, gravitational mass, and tidal deformability.
Winter 2023
January 13, 2023

Prof. J. Lajoie, Harmon-Ye, Iowa State University

From sPHENIX at RHIC to ePIC at the EIC

Abstract

The sPHENIX detector currently under construction at Brookhaven National Laboratory's Relativistic Heavy Ion Collider (RHIC) is designed to significantly advance studies of the microscopic nature of nuclear matter. The experiment incorporates full azimuth vertexing, tracking, and a complete set of electromagnetic and hadronic calorimeters over the pseudorapidity range |η| < 1.1. This powerful detector system is coupled with a high rate DAQ in order to deliver unprecedented data sets enabling a wide range of jet measurements at RHIC. sPHENIX has an extensive a multi-year physics program planned which includes Au+Au, polarized p+p and p+Au collisions. In particular, the use of jets as a probe in p+p/p+A and e+A collisions allows access to the interaction of the hard-scattered partons with the nuclear environment and is sensitive to a wide range of scales. Measurements of jets and jet substructure in these systems will provide unprecedented access not only to nuclear PDFs and saturation, but spin-orbit correlations in the nucleon through measurements of the Sivers and Collins asymmetries and how these observables can be modified in a nucleus. The Electron Ion Collider (EIC), to be built by JLab and BNL, will be unique in colliding polarized electrons off polarized protons and light nuclei, providing the capability to study multi-dimensional tomographic images of protons and nuclei, and collective effects of gluons in nuclei. In this talk I will both present an overview of jet and jet substructure measurements in sPHENIX at RHIC and highlight the complementarity between p+p/p+A collisions at RHIC and e+A collisions at the future EIC.
Fall 2022
December 16, 2022

Prof. Anthony Timmins, University of Houston

Future studies with the ALICE experiment

Abstract

The ALICE experiment was built to study many-body Quantum Chromo-Dynamics (QCD) at high temperature and effectively zero baryon density, using relativistic heavy-ion collisions at the Large Hadron Collider (LHC). These collisions form the Quark Gluon Plasma (QGP), a state of matter where quarks and gluons are no longer confined inside hadrons. The ALICE program centers around the key questions related to QGP phenomena. These include the macroscopic and microscopic properties of the QGP, and the details of the QGP phase transition to hadrons, that is believed to have taken place in the early Universe. At the same time, ALICE's versatile setup allows for the study of pp collisions, p--Pb collisions, and ultra-peripheral collisions. The associated studies can provide some of the most stringent tests of QCD and Beyond Standard Model searches. They serve as deep probes of the properties of cold nuclear matter and allow for investigations of stellar and interstellar phenomena. I will discuss the planned upgrades for the ALICE experiment that will occur in the 2020s and 2030s. Prospects for future measurements will be presented in light of these upgrades.

December 2, 2022

Dr. Agnieszka Sorensen, University of Washington

The equation of state of dense nuclear matter from heavy-ion collisions

Abstract

In this talk, I will discuss progress on constraining the equation of state (EOS) of symmetric dense nuclear matter, as described in arXiv:2208.11996. The study uses hadronic transport simulations with parametrizable mean-field interactions together with flow data from the STAR experiment at the center-of-mass energies of 3.0 and 4.5 GeV to constrain the EOS through Bayesian analysis. I will discuss the findings in the context of other known constraints from heavy-ion collisions and neutron star studies. I will also outline developments in state-of-the-art hadronic transport codes necessary to fully utilize the potential of the forthcoming data from the BES-II FXT program at RHIC to constrain the EOS of symmetric dense nuclear matter.

November 18, 2022

Dr. Amruta Joadand, Caltech

The Enigmatic Transitional millisecond pulsar, PSR J1023+0038: Discovery of UV millisecond pulsations

Abstract

Transitional millisecond pulsars (tMSPs) switch between a low-mass X-ray binary (LMXB) and a radio millisecond pulsar (RMSP) state, establishing a firm evolutionary link between the two source classes. tMSPs provide a great avenue to study the low-level accretion processes that spin up pulsars to millisecond periods. Systematic, multi-wavelength observational campaigns over the last decade have resulted in surprising findings such as i) persistent, multi-year-long, low-level (Lx <10^34 ergs/s) accretion state with coherent pulsations; ii) radio outflows, and iii) uninterrupted pulsar spin down in the X-rays. In this unique state, we have now found the first known UV millisecond pulsar with a dedicated multi-wavelength campaign involving the Hubble space telescope. In my talk, I will review the observational understanding of tMSPs while highlighting this exciting discovery which challenges our understanding of low-level accretion and pulsed emission in neutron stars.

November 11, 2022

Dr. Nicole Lewis, Brookhaven National Laboratory

Baryon Stopping in Photonuclear Collisions

Abstract

Photonuclear collisions are one of the simplest processes that can happen in a heavy-ion collision. They occur when one nucleus emits a quasi-real photon that interacts with the other colliding nucleus, similar to an electron-ion collision except that the photon tends to have a much smaller virtuality. Photonuclear collisions can be used to study bulk properties of the medium such as collectivity due to initial-state effects and hadron chemistry. In these photonuclear collisions, we observed baryon stopping: more baryons that antibaryons even at angles perpendicular to the beam line. This phenomenon is well documented in proton-proton and heavy-ion collisions, but it is not well understood and has never before been seen in photonuclear collisions. This could indicate the existence of a baryon junction within the nucleon, a nonperturbative Y-shaped configuration of gluons that carries the baryon number and is attached to all three valence quarks. These measurements will also help inform future measurements using particle identification at the upcoming Electron Ion Collider.

November 4, 2022

Dr. Yoni Khan, Illinois University

Muon beam searches to probe the g-2 anomaly

Abstract

The recent results from the Fermilab g-2 experiment have reinforced the tension between the experimental measurement and the Standard Model prediction for the anomalous magnetic moment of the muon, now at more than 4 sigma. In this talk, I will assume that the anomaly is real and describe how a program of muon beam experiments at a variety of energy scales could definitively uncover the new physics that could resolve it, regardless of the underlying model. At a minimum, there must be one new particle that couples to the muon, which can be discovered at fixed-target muon beam experiments or at a low-energy muon collider. If the new particle has electroweak charges, the observed value of the anomaly permits new particle masses up to the 100 TeV scale, which can be discovered at a muon collider either through direct production or indirectly through their contributions to rare processes. The non-observation of any new physics at a 30 TeV muon collider would have profound implications for naturalness, flavor, and unitarity.

October 28, 2022

Prof. Meenakshi Narain, Brown University

Exploring the Particle Universe at the Large Hadron Collider

Abstract

The Large Hadron Collider (LHC) at CERN, Switzerland, is currently the world's most powerful particle accelerator. During 2015-2018 (Run 2 era), it has delivered an unprecedented amount of proton-proton collision data at a center-of-mass energy of 13 TeV. I will present some of the highlights from its extensive physics program ranging from studies of the Higgs Boson properties to the searches for physics in unchartered territories beyond those predicted by the Standard Model. In addition, starting around 2027+, the High-Luminosity LHC (HL-LHC) will deliver proton-proton collisions at a center-of-mass energy of 14 TeV. I will summarize the exciting new hardware developments that are underway in CMS and the physics opportunities they open up at the HL-LHC.

October 21, 2022

Dr. Kristen Dage, McGill University

Ultraluminous X-ray Sources in Extragalactic Globular Clusters

Abstract

Currently, ultraluminous X-ray sources (ULXs) with globular cluster (GC) counterparts have been identified. This is exciting, as ULXs have been theorized as potential intermediate-mass black holes. New black hole mergers detected by LIGO-Virgo may also be associated with GCs, underscoring the importance of ULXs as a potential linkage between GC electromagnetic and gravitational wave source populations. GC ULXs show a diverse behavior with regards to temporal variability, both on long (16 years) and short (~hours) timescales, in both the X-ray and optical wavelengths. They can switch on or off over the course of many years or remain at a constant luminosity. Some sources exhibit a long-term change in their luminosity with no discernible variability within the other observations, other sources show a stunning long-term variability while also demonstrating variability on the timescale of around four hours. I will undertake a comprehensive comparison of the temporal variability of the zoo of currently known GC ULXs, discuss the possible origins of some of the extreme variability observed, and how this informs our knowledge of black hole populations in extragalactic globular clusters.

October 7, 2022

Lopamudra Mukherjee, University of Mississippi

Survey of FCNC in Light Dark Vector Boson Models

Abstract

In this talk, I will take you through different light vector boson models and illustrate their fate in context to flavor-changing neutral current decays of the B- and K-meson. Contrary to the findings of an earlier work, due to the correct calculations of the FCNC amplitudes, we report that O(1) couplings are not required to fit the data on rare and flavor-changing B and K decays. We also include a robust treatment of hadronic decays of dark Z in its width. However, we also find that the allowed parameter region, in spite of providing a very good fit to the b -> s l+ l− data, is ruled out from various other constraints from low energy measurements such as the atomic parity violation, K+ -> mu+ + invisible decay, Bs − Bs-bar mixing, etc.

September 23, 2022

Dr. Ilaria Vai, CERN & University of Bergamo, Italy

A new generation of gaseous detectors for the CMS experiment

Abstract

The future of gaseous detectors technology relies on Micropattern Gaseous Detectors (MPGDs): they can reach extreme rate capabilities, space resolutions and are resistant to radiations, fundamental characteristics for nowadays high energy physics experiments. Gas Electron Multipliers in particular have gone through a 20-year-long R&D phase that led them to become a mature technology, ready for operation in large experiments.

In this seminar I will focus on the R&D that the CMS collaboration has been doing on Triple-GEM detectors: we will look at the rationale behind the choice of this technology for the upgrade of the muon system. I will then describe the performance achieved in test beams and in laboratory qualification. Finally, I will outline how the Triple-GEM detectors were installed in the experiment and focus on the results obtained during commissioning and in the early stages of data taking with cosmic rays and beam.

September 16, 2022

Hannah Bossi, Yale University

Investigating the R-dependence of jet suppression in ALICE using machine learning techniques

Abstract

At sufficiently high temperatures, QCD matter becomes a hot and dense medium known as the quark-gluon plasma (QGP). The QGP can be experimentally recreated through the collisions of relativistic heavy ions. Hard scattered partons in high-energy collisions fragment and hadronize to form a spray of particles called a jet. Jets in heavy-ion collisions interact with the QGP, leading to so-called "jet quenching" effects such as a suppression of jet yields and modification of internal jet structure that can be used to constrain the properties of the QGP. The dependence of jet suppression on the jet radius (R) and jet pT is a useful observable to disentangle competing energy loss mechanisms. Due to the presence of the large underlying event in heavy-ion collisions, measurements at large R and low pT are limited by the pT resolution using traditional techniques. A new method using machine learning techniques is used to correct the large background in heavy-ion collisions and extend the measurement of inclusive jet yields to lower pT than previously achieved in heavy-ion collisions at the LHC. This talk will present the inclusive jet nuclear modification factors in Pb–Pb collisions in various centrality classes at root-s = 5.02 TeV recorded with the ALICE detector for resolution parameters up to R = 0.6 for jet transverse momenta down to 40 GeV/c. These results suggest that jets reconstructed with larger resolution parameters are more suppressed. Comparisons with jet quenching models will also be shown.
Winter 2022
April 22, 2022

Dr. Jean-François Paquet, Duke University, US

The quark-gluon plasma: multi-messenger nuclear physics, microscopic relativistic fluids and big dat

Abstract

The quark-gluon plasma is a new phase of matter that can be produced by colliding large nuclei at velocities close to the speed of light. This plasma is both the smallest and hottest liquid ever produced, extending the size of a few proton radii but reaching temperatures higher than those found in the most extreme astrophysical events. The explosive expansion of this plasma can be described with relativistic fluid dynamics, and provides a window into the equation of state and transport coefficients of strongly coupled nuclear matter. I present recent constraints on the viscosities of the quark-gluon plasma, obtained through a large-scale Bayesian analysis combining measurements from two collider experiments. I discuss electromagnetic radiation from the quark-gluon plasma and their potential to provide additional constraints on the viscosities.

April 1, 2022

Prof. Keri Vos, Maastricht University, The Netherlands

B mesons as a telescope for new physics

Abstract

B meson decays are important players in the search for physics beyond the Standard Model (SM) of particle physics. Linked to the antimatter-matter asymmetry in the universe, a key interest in this is also improving the understanding of the mechanism of CP violation within the SM. The large amount of data gathered by the B factories and LHCb allows testing the SM with an unprecedented precision, probing scales much higher than the reach of direct searches at the LHC. Naturally, this also requires precise theoretical predictions. In this talk, I will present some of the challenges and new ideas to push the theoretical precision up. Specifically, I will focus on the determination of the CKM element Vcb and QED effects in non-leptonic decays.

March 4, 2022

Prof. Gunther Roland, Massachusetts Institute of Technology, US

February 25, 2022

Prof. You Zhou, University of Copenhagen, Denmark

February 18, 2022

Dr. Bjoern Schenke, Brookhaven National Laboratory, US

February 11, 2022

Prof. Kevin Kelly, Texas A&M University, US

Where we’re going with neutrino oscillation experiments

Abstract

In the last several decades, neutrino oscillations have gone from an experimental anomaly to robust evidence for beyond-the-Standard-Model physics. While much has been learned since the first experiments, several aspects of oscillations remain unknown, including the degree to which CP is violated in the lepton sector. In this talk, I will explore our current knowledge of neutrino oscillations, and discuss how the next generation of experiments can further enlighten us. These upcoming experiments have the ability to test “standard” and BSM neutrino oscillation hypotheses, as well as a multitude of non-neutrino BSM physics scenarios.

February 4, 2022

Prof. Chun Shen, Wayne State University, US

Longitudinal dynamics and particle production in relativistic nuclear collisions

Abstract

In this talk, I will present an improved three-dimensional dynamical initialization model for relativistic heavy-ion collisions, implementing local energy-momentum conservation and baryon charge fluctuations at string junctions. These improvements lead to an excellent description of the charged hadron and net proton rapidity distributions in Au+Au collisions from 7.7 to 200 GeV and Pb+Pb collisions at 8.77 and 17.3 GeV. Based on these results, we quantify the amount of baryon stopping at the initial impact and baryon transport during the hydrodynamic evolution and hadronic scattering phases. The effects of baryon stopping and strangeness neutrality on identified particle yields are quantified as a function of collision energy. We further expand the model description to asymmetric p+Al and (p, d, $^3$He)+Au collisions at the top RHIC energy and p+Pb, Xe+Xe, and Pb+Pb collisions at LHC energies. The particle rapidity distributions in asymmetric collision systems can provide crucial constraints on modeling the early-time longitudinal dynamics.

January 28, 2022

Dr. Sigtryggur Hauksson, IPHT, CEA-Saclay, France

Anisotropic jet momentum broadening and jet polarization

Abstract

Heavy-ion collisions produce high-temperature QCD matter known as the quark-gluon plasma (QGP). Jets probe the QGP as they traverse the medium and undergo transverse momentum broadening. Recent work has shown that this momentum broadening is highly anisotropic in the early stages of heavy-ion collisions.

In the first half of this talk, we analyze in detail how anisotropic momentum broadening leads to net polarization of jet partons emitted in medium-induced bremsstrahlung. Jet polarization could therefore give a new way of measuring medium anisotropy.

In the second half of the talk, we provide our own calculation of jet broadening in an anisotropic, weakly-coupled quark-gluon plasma. A main result is that momentum broadening is substantially reduced at lower momenta compared with an equilibrium medium.

January 21, 2022

Prof. Bryce Littlejohn, IIT, Illinois, US

Search for an excess of electron neutrino interactions in MicroBooNE using multiple final state topologies

Abstract

I will present a measurement of electron neutrino interactions from the Fermilab Booster Neutrino Beam using the MicroBooNE liquid argon time projection chamber performed to address the nature of the excess of low energy interactions observed by the MiniBooNE collaboration. Observation of an excess of electron neutrino detections in MicroBooNE would represent clear evidence of new physics in the neutrino sector, such as the existence of new neutrino mass states beyond those associated with the three Standard Model neutrinos. Three independent electron neutrino searches were performed by MicroBooNE across multiple single electron final states, including an exclusive search for two-body scattering events with a single proton, a semi-inclusive search for pion-less events, and a fully inclusive search for events containing all hadronic final states. With differing signal topologies, statistics, backgrounds, reconstruction algorithms, and analysis approaches, the results are found to be consistent with the nominal electron neutrino rate expectations from the Booster Neutrino Beam and no excess of electron neutrino events is observed. I will summarize important details of MicroBooNE's new centerpiece result, while also providing some broader context on its impact on searches for physics beyond the Standard Model in the neutrino sector.

January 14, 2022

Prof. Tien-Tien Yu, University of Oregon, US

Solar Neutrinos: from background to signal

Abstract

Solar neutrinos are an inevitable background to any dark matter direct detection experiment as they closely mimic the signature of dark matter. In this talk, I will discuss the effects of solar neutrinos on the reach of dark matter-electron scattering experiments, with a focus on semiconductor and noble liquid detectors. In addition, I will present the prospects of measuring and understanding the various solar neutrino components using the same detectors, as well as the effects of non-standard neutrino interactions, thus turning solar neutrinos from a background to an interesting signal in their own right.

Slides
Fall 2021
December 10, 2021

Professor Anne Lohfink, Montana State University

Traffic patterns around accreting black holes

Abstract

Black hole accretion is one of the most energetic processes in the Universe, making the surrounding of black holes a place of many extremes and an interesting study target. Despite a wealth of studies, many open questions remain. In my talk, I will discuss new results regarding two of those remaining questions. Initially, I will explore the question of whether the torus structure observed near accreting supermassive black holes is the same for sources with strong obscuration (Seyfert 2s) and sources with little obscuration (Seyfert 1s). To shed light on this matter, I will present results from an X-ray and IR study of the torus in a sample of polar-scattered Seyferts. The second half of my talk will then focus on the connection of the accretion process to the compact jet, as it is seen in the hard state of black hole X-ray binaries but also in some AGN.

Slides

December 3, 2021

Dr. Rob Pisarski, Brookhaven National Lab, US

Three of four things in Extreme QCD

Abstract

I discuss several topics relevant to the phase diagram of QCD at nonzero temperature and density. This includes the possible appearance of a "Quantum Pion Liquid" at low temperatures and density; how to find a "moat" spectrum, necessary for a QpiL, in heavy ion collisions; the solution of nuclear matter in 1+1 dimensions; and what the lattice tells us about the relation between the chiral and deconfining transitions.

November 19, 2021

Professor Piotr Bożek, AGH University, Krakow, Poland

Mapping flow fluctuations in heavy-ion collisions

Abstract

Collective flow in heavy-ion collision undergoes event-by-event fluctuations. The azimuthally asymmetric flow generated in each event fluctuates in its magnitude and direction for each harmonic. Another aspect of the flow fluctuations manifests itself in the decorrelation of flow vectors measured in two different kinematic bins. The decorrelation of the flow can be measured as the flow factorization breaking coefficient at two different rapidities or at two different transverse momenta. We discuss possible mechanisms leading to such effects. The flow vector decorrelation can be due to the flow magnitude of or flow angle decorrelation. The two effects can be separated by measuring the factorization breaking for higher moments of harmonic flow coefficients. We briefly discuss how the two contributions are related in a simple model. The separation of flow magnitude and flow angle decorrelation can be also studied for the nonlinear flow coupling between flow harmonics of different order.

Slides

November 12, 2021

Dr. Bhupal Dev, Washington University, US

Hints of SUSY in Flavor Anomalies?

Abstract

The recent results from the Fermilab muon g − 2 experiment, as well as the persisting hints of lepton flavor universality violation in B-meson decays, present a very strong case for flavor-nonuniversal beyond the Standard Model physics. We will discuss a minimal R-parity violating supersymmetric framework with relatively light third-generation sfermions (dubbed as ‘RPV3’), which provides a simultaneous explanation of all flavor anomalies. We will also discuss complementary tests and distinct signatures of this scenario in the high-pT searches at current and future colliders.

October 29, 2021

Professor Giorgio Torrieri, Unicamp, Brazil

Hints of SUSY in Flavor Anomalies?

Abstract

The observation, in hadronic collisions, of "ideal fluid" type behavior in systems of a comparatively small number of particles, presents a conceptual puzzle, since the way we usually derive hydrodynamics is via approximating "many" particles as a continuum. I will argue that making sense of this requires re-deriving relativistic hydrodynamics as a "bottom-up" theory, with no reference to microscopic physics except the local emergence of a thermalized system. This is in contrast to usual attempts to understand hydrodynamics as a "top-down" theory, in terms of models such as transport and holographic strongly coupled systems. We attempt to do this using basic statistical mechanics and find the apparently counter-intuitive conclusion that in the small viscosity limit, it might indeed be that smaller systems could thermalize faster.

Slides

October 22, 2021

Dr. Maíra Dutra, Carleton University, Canada

Testable portal models of FIMP dark matter

Abstract

Dark matter particles can interact so weakly with the standard model fields that they may never have reached thermal equilibrium in the early universe. The relic density of such feebly interacting massive particles (FIMPs) is produced via the so-called freeze-in mechanism. This possibility can explain why we have not yet detected dark matter but is also appealing from a theoretical perspective since tiny couplings might be a consequence of heavy particles needed to solve different puzzles in particle physics. In this talk, I will present two testable models of FIMP dark matter. The first model is a neutrino portal where three right-handed heavy neutrinos participate in the type-I seesaw mechanism while mediating interactions between the visible and dark sectors. If a sufficiently long early matter-dominated period occurred during the freeze-in process, FIMP self-annihilation becomes testable by indirect detection experiments. The second model is a Z' portal in which the SM fermions and a fermionic dark matter candidate are both charged under a new U(1) symmetry. Remarkably, the rich phenomenology of Z' bosons is currently constraining regions of the Z' parameter space in which the dark matter relic density is achieved via freeze-in.

Slides

October 15, 2021

Professor Francesco Becattini, University of Florence, Italy

Recent developments of spin physics in relativistic heavy ion collisions

Abstract

Spin is a relatively new topic in the rather mature field of relativistic heavy ion collisions and it has attracted much interest over the past few years. The predictions of the hydrodynamic model of the Quark Gluon Plasma have been confirmed by the measurements of global spin polarization of Lambda hyperons. However, the measurements of spin polarization as a function of the hyperon momentum revealed consistent discrepancies with respect to the theoretical predictions. In this talk, I will first present some recent theoretical developments which imply a solution of the local polarization puzzles. In the second part, I will show that spin can be used as a probe of local parity violation in heavy ion collisions, an effect that has been long sought through the well-known Chiral Magnetic Effect. By measuring Lambda helicity correlation as a function of the difference of their azimuthal angles, it is in principle possible to find evidence of local parity violation without the involvement of the electromagnetic field.

Slides

October 8, 2021

Professor Nathaniel Craig, University of California, Santa Barbara

Is Nature Natural? The Electroweak Hierarchy Problem Circa 2021

Abstract

The discovery of the Higgs boson at the LHC marks the culmination of a decades-long quest for the final piece of the Standard Model. But the discovery of the Higgs also adds new urgency to the hierarchy problem, namely the question of why the Higgs boson is so light despite its unique quantum sensitivity to much higher energy scales. This puzzle is made all the more challenging by the lack of evidence for conventional approaches to the hierarchy problem at the LHC and other experiments. In this talk, I'll discuss the essential features of the hierarchy problem and its many possible solutions — ranging from the familiar to the highly speculative — with a particular focus on new developments.

October 1, 2021

Dr. Zhangbu Xu, Brookhaven National Laboratory, USA

How STAR discovered the Breit-Wheeler Process and Vacuum Birefringence

Abstract

In 1934, Breit and Wheeler predicted that collisions of photons could create matter/antimatter, even suggesting doing so by accelerating heavy ions as the only viable approach. Heisenberg, Euler (1936) and Toll (1952) predicted vacuum polarization in magnetic field, and the refractive index depending on the photon polarization. At relativistic velocity, the spiraling magnetic and perpendicular electric fields generated by ultra-relativistic heavy ions, are of equal strength—which is the definition of a photon, a quantized “particle” of light. It provides an ideal physical laboratory for testing strong field QED.

The STAR collaboration investigated if collisions of photons surrounding RHIC’s ions could be uniquely identified as the Breit-Wheeler process. We studied 6085 e+e- pairs produced in UPC collisions. All available kinematic variables of the electron-positron pairs are studied with this high-statistics data sample. By correlating the photons’ momentum, spatial location, and polarization with experimental observables, we assessed that the transverse momentum vectors of photons were driven by the local electromagnetic field, not by Heisenberg’s uncertainty principle randomly determined by the nuclear size. Following a newly proposed method, we discovered a striking fourth-order azimuthal distribution of (16.8+-2.5)%. The high-precision data were consistent with particles being generated by real photon interactions, rather than from highly virtual photons. We experimentally investigated the spatial distribution of the electromagnetic field and the dependence of photon interaction cross-section on the polarization angle relative to the magnetic field. The experimental results have implications for vacuum birefringence and for mapping the magnetic field which is important for emergent QCD phenomena.

Slides

September 24, 2021

Professor Sergei A. Voloshin, Wayne State University

Search for the Chiral Magnetic Effect: Recent results from isobar collisions at RHIC

Abstract

The chiral magnetic effect (CME) is predicted to occur as a consequence of a local violation of P and CP symmetries of the strong interaction amidst a strong magnetic field generated in relativistic heavy-ion collisions. Experimental manifestation of the CME involves a separation of positively and negatively charged hadrons along the direction of the magnetic field. Previous measurements of the CME-sensitive charge-separation observables remain inconclusive because of large background contributions. In order to better control the influence of signal and backgrounds, the STAR Collaboration has performed a blind analysis of a large data sample of approximately 3.8 billion isobar Ru+Ru (ARu = 96, ZRu = 44) and Zr+Zr (AZr = 96, ZZr = 40) collisions at the top RHIC energy. Prior to the blind analysis, the CME signatures were predefined as a significant excess of the CME-sensitive observables in Ru+Ru collisions over those in Zr+Zr collisions, owing to a larger magnetic field in the former. This presentation reports on the findings from the isobar blind analysis and their significance for the CME search in heavy-ion collisions.

Slides

September 17, 2021

Dr. Soumya Mohapatra, Columbia University, US

Investigating the quark-gluon plasma in proton-proton collisions

Abstract

The quark-gluon plasma (QGP) is a phase of QCD matter that occurs at temperatures of a few trillion Kelvin, wherein the degrees of freedom are not colorless hadrons but deconfined quarks and gluons. The QGP occurred naturally in the early universe a few microseconds after the Big Bang when the temperature of the universe was above the deconfinement temperature. The QGP can be recreated in particle colliders by colliding "heavy" nuclei, like lead or gold, at relativistic energies. Until a few years ago, it was believed that the QGP could only be recreated in such "heavy-ion" collisions. However, measurements in proton-proton (pp) collisions showed the presence of features that are strikingly similar to those observed in heavy-ion collisions. This raises the possibility that a tiny droplet of the QGP is produced even in pp collisions. However, these features can also be qualitatively reproduced by theoretical models that attribute their origin to semi-hard processes. In this talk, I will present several recent measurements that aim to establish whether or not the QGP is produced in pp collisions.

Slides

September 10, 2021

Professor Peter Christiansen, Lund University, Sweden

Studying dense QCD dynamics with quantum number balance

Abstract

The strangeness enhancement observed by ALICE in small collision systems has led to a confrontation between traditional pp models, in which high-multiplicity pp collisions are an almost incoherent sum of parton-parton collisions (e.g., PYTHIA), and QGP-like models, where the parton-parton collisions lead to the formation of a medium. To differentiate between these models (and their extensions), we have done a new series of measurements where we have tried to determine how the strangeness and baryon number of a Xi baryon (B=+1, S=-2) is balanced (B=-1, S=+2) by other hadrons. In this way, we wanted to measure if there is evidence that the quarks directly form hadrons (close correlations in momentum space) or that there is significant diffusion between quark production and hadronization (longer range correlations). The data seems to favor short-to-medium range correlations and a weak multiplicity dependence (unlike for the strangeness enhancement itself).

In the second half of the talk, I will therefore speculate that maybe these correlations are limited by an intermediate phase that we denote the gluon plasma (GP) and where there are few light quarks. In this picture, the hydrodynamization ("modern version of thermalization") is driven by gluons and it is first late that quark pairs appear and therefore their diffusion is small. This scenario, related to the old idea of Hot Glue, has potentially many nice features (photon flow and little or no CME). To test this idea we propose to extend the Xibaryon studies to study how charm and anticharm hadrons balance, since charm will be produced in the initial interactions and therefore be able to probe the full evolution of the collision. Finally, we also discuss how these ideas can be used to test the idea of J/psi regeneration.

Slides

September 3, 2021

Professor Jamie Nagle, University of Colorado at Boulder

What is the end game in heavy-ion physics?

Abstract

Exciting times are ahead with the running of sPHENIX and STAR with forward upgrades at RHIC and Run-3 starting at the LHC. At the same time, heavy ion running at RHIC will be ending this decade as construction of the Electron Ion Collider gets underway. In this talk, I will review some key findings from RHIC that have taken advantage of the flexibility of the machine. I will put these results in context in terms of the "end game" of the program and what we have learned and what remains.

Slides
Winter 2021
May 7, 2021

Prof. Dr. Mattia Dalla Brida, CERN

The energy-momentum tensor of QCD from a moving frame

Abstract

The energy-momentum tensor (EMT) is a fundamental quantity of any quantum field theory. In QCD, in particular, its correlation functions encode information on the thermodynamic properties of the quark-gluon plasma, as well as on the internal structure of hadrons. Quantitative determinations of these properties require a non-perturbative solution of the theory. At present, lattice QCD is the only known method that allows for first-principles non-perturbative calculations. The application of these techniques, however, necessitates a proper non-perturbative definition of the EMT. The problem is in fact non-trivial due to the explicit breaking of (Euclidean) Poincare' symmetry by the lattice regularization. In this talk, we review the difficulties in devising a practical definition of the EMT in lattice QCD, and present a novel framework to address the problem. The latter is based on studying QCD at finite temperature from the point of view of an observer in a moving reference frame. We shall present how within this framework it is possible to find many compelling identities through which the EMT can be defined. In addition, new ways to compute thermodynamic quantities are possible.

Slides

Recording

April 30, 2021

Prof. Dr. Jean-Yves Ollitrault, Institut de Physique Théorique, CEA Saclay

Effective viscosities for anisotropic flow

Abstract

Determining the transport coefficients of the quark-gluon plasma, such as its shear (η) and bulk (ζ) viscosities, is one of the goals of heavy-ion physics. An important question is how their temperature dependence can be constrained using experimental data. The observable that is most sensitive to the viscosity is anisotropic flow. I show that in relativistic hydrodynamics, the damping of elliptic and triangular flows is determined by an effective viscosity, which is independent of the system size and centrality. This in turn means that this effective viscosity is the only quantity that can be extracted from data at a given collision energy. It is the sum of effective shear and bulk viscosities, each of which is a weighted average of the temperature-dependent viscosity. The effective shear viscosity is driven by the lowest temperatures, just above freeze-out, while the effective bulk viscosity is driven by somewhat higher temperatures.

Paper

Slides

Recording

April 23, 2021

Prof. Michael Lisa, The Ohio State University

Subatomic Smoke Rings: Polarization and Toroidal Vorticity in the QGP

Abstract

Since the discovery of global hyperon polarization in Au+Au collisions at RHIC about five years ago, there has been intense theoretical and experimental focus on the topic. After a brief review, I will discuss novel vortex structures that may be generated in two situations. The first is a p+A collision, which may produce droplets of QGP that develop a toroidal vortex ("smoke ring") structure. Experimental observation of such a structure would provide compelling evidence supporting the hydrodynamic nature of this tiny system, a much-debated topic today. The other is an idealized "hot moving spot" that may result from the thermalization of a jet in an expanding QGP; in this case, the "smoke ring" centers on the jet direction. In both cases, we suggest an experimental observable to measure the toroidal vortex structure, and present full hydrodynamical simulations to make quantitative predictions. I will also discuss next steps for more realistic calculations.

Paper

Paper

Recording

April 16, 2021

Prof. Dr. Xin-Nian Wang, Lawrence Berkeley National Laboratory

Surfing the wake of the jet-induced shock-wave in a quark-gluon plasma

Abstract

Jets in QCD have become a powerful tool in high-energy particle and nuclear physics since the concept was developed in the 70's. They have been used to study properties of the quark-gluon plasma (QGP) in high-energy heavy-ion collisions through the jet quenching phenomenon. Jet quenching is caused by parton energy loss when an energetic parton propagates through the QGP medium. Since the parton travels at the speed of light which is much faster than the velocity of sound inside a QGP, such energy loss to the medium will generate a supersonic shock wave. In this talk, I will discuss recent renewed efforts to search for such a shock wake and how to use it to study properties of the QGP in high-energy heavy-ion collisions.

Recording

April 9, 2021

Dr. Christopher Plumberg, University of Illinois at Urbana-Champaign

Constraining Relativistic Hydrodynamic Behavior in Nuclear Collisions

Abstract

Hydrodynamics is a ubiquitous phenomenon in nature. It also provides a remarkably powerful description of the space-time evolution of relativistic nuclear collisions. Nevertheless, understanding its success in such systems is far from trivial. To date, several indicators have been developed to quantitatively assess the validity of relativistic hydrodynamics quite generally, including systematic expansions in deviations from local equilibrium, expansions in thermodynamic gradients, and constraints imposed by relativistic causality. In this talk, I will discuss some recent progress in exploring the applicability of relativistic hydrodynamics to both small and large nuclear collisions, using a number of these quantitative indicators to assess its validity. I will focus in particular on recent findings concerning large violations of causality in state-of-the-art numerical simulations of p+Pb, O+O, and Pb+Pb collisions at the LHC. I will also discuss some of the implications of these findings for further constraining our understanding of nuclear collision evolution.

Slides

Recording

April 2, 2021

Dr. Daniel Tapia Takaki, University of Kansas

Entanglement and Quantum tomography for collider physics

Abstract

Quantum mechanics is experiencing an experimental and theoretical renaissance. In this talk, we will discuss novel ways to use quantum mechanics and provide several experimental applications of quantum tomography for proton-proton and heavy-ion collision experiments at the CERN Large Hadron Collider. We will discuss application of this model-independent analysis technique for Z bosons, dijets and quarkonia. The first observation of an unexpected correlation of spin and momentum in the experimental data will also be presented.

Recording

March 26, 2021

Dr. Giuliano Giacalone, ITP Heidelberg

Correlating isotropic flow with anisotropic flow in heavy-ion collisions: nuclear phenomenology at high energy beyond the quark-gluon plasma

Abstract

Experiments conducted at the Relativistic Heavy Ion Collider and at the Large Hadron Collider have established that the interaction of two nuclei at relativistic energy creates a small droplet of quark-gluon plasma (QGP), whose dynamics, from its formation till its fragmentation into hadrons, can be effectively described with the laws of relativistic (viscous)hydrodynamics. I argue that the great success of this hydrodynamic description permits us to search for exciting nuclearphenomena beyond the original purposes of the heavy-ion program. Experimentally, this can be achieved by looking at somewhat unconventional multi-particle correlation observables, where the measures of the anisotropy of the emission of hadrons, the so-called flow coefficients, v_n, are correlated with the magnitude of the isotropic emission, i.e., the average transverse momentum, , of the hadron spectrum. I show that these v_n- correlations provide in particular: i) a novel means to observe deformations in the geometric shape (structure) of the colliding ions; ii) a handle to manipulate the strong electromagnetic fields produced in the interaction of nuclei at high energy; iii) a way to trigger manifestations of the correlation of gluon fields in the pre-QGP stages of the collision process. I point out a few additional phenomena that can be analyzed with the same techniques, and emphasize that the upcoming experimental advances (LHC 3&4, sPHENIX, STAR forward upgrade) will enable us to pursue such studies with success over the next decade.

Recording

Slides

March 19, 2021

Dr. Jasmine Therese Brewer, CERN

Slow modes in the rapidly-expanding quark–gluon plasma

Abstract

A crucial question in understanding the onset of hydrodynamic behavior in the quark–gluon plasma is whether hydrodynamics is “unreasonably effective” in describing systems far-from-equilibrium. This is motivated by the observation that many models of expanding systems exhibit an apparent simplification in their description while gradients are large and hydrodynamics is not expected to apply. We provide a new conceptual approach to understanding this simplification based on far-from-equilibrium slow modes. For a class of collision integrals in kinetic theory, these slow modes can be explicitly identified as the instantaneous ground states of an effective Hamiltonian describing the evolution of moments of the distribution function. They are qualitatively distinct from hydrodynamic modes when the system is far from equilibrium, suggesting that the simplification is not directly related to the onset of hydrodynamics. Importantly, these slow modes dominate the evolution when gradients are small compared to the energy gap, which occurs both at early times and in the hydrodynamic limit.

Slides

Recording

March 5, 2021

Prof. Alakabha Datta, University of Mississippi

Light Particles and Flavor Anomalies.

Abstract

Weakly coupled light states like the dark photon or the dark Higgs have been discussed extensively. I will discuss a few flavor anomalies that could indicate the presence of light particles. These anomalies are in B and K decays, g-2 measurements of the charged leptons and in neutrino oscillation experiments. While most of the discussion will employ a general description of the interactions of these light states I will also present a specific model of a dark Higgs that mixes with a 2HDM Higgs sector.

Slides

Recording

February 26, 2021

Prof. Dr. Raju Venugopalan, Brookhaven National Laboratory, Stony Brook University

The chiral anomaly and the proton's spin: axion-like dynamics and spin diffusion via topological transitions

Abstract

The proton's spin arises fundamentally from the complex many-body dynamics of its spinning quark and gluon constituents. In Quantum Chromodynamics, this dynamics is strongly influenced by the chiral anomaly, a property of the QCD vacuum not manifest in the equations of motion. We will outline the key elements of a powerful formalism where the role of the anomaly is made manifest and show that the appropriate treatment of the anomaly is deeply tied to the resolution of the so-called U_A(1) problem in QCD. At high energies, we conjecture that the corresponding emergent dynamics is analogous to that of a popular dark matter candidate, the axion, with spin diffusion occurring via topological "sphaleron" transitions. These ideas have strong bearing on searches for the Chiral Magnetic Effect at RHIC and can be cleanly tested at a future Electron-Ion Collider.

February 19, 2021

Dr. Sören Schlichting, Universität Bielefeld

Jet quenching and equilibration in Heavy-Ion collisions

Abstract

We investigate the medium induced fragmentation of jets in a high-temperature QCD plasma. Based on an effective kinetic theory of QCD, we study the non-equilibrium evolution of the jet shower [1] and the chemical equilibration of jet fragments in the medium [2]. By including radiative emissions as well as elastic interactions, our approach extends all the way from the jet energy scale to the temperature of the medium and includes important effects such as the recoil of the medium. We present results for the in-medium fragmentation, including chemical and kinetic equilibration of the soft fragments [1,2] and discuss implications of our result to jet quenching physics and the problem of thermalization of the quark-gluon plasma in heavy ion collisions.

[1] Y.Methar-Tani, S.Schlichting JHEP 09(2018) 144
[2] S.Schlichting, I. Soudi arXiv:2008.04928[hep-ph]

Slides

Recording (Link will become inactive 6 months after February 19, 2021)

February 12, 2021

Dr. Konrad Tywoniuk, University of Bergen

Energy loss of QCD jets in heavy-ion collisions

Abstract

The quark-gluon plasma (QGP) created in high-energy heavy-ion collisions at RHIC and LHC is opaque to energetic and heavy particles that are created in short-distance particle scattering. Jets, aligned collections of energetic hadrons resulting from the fragmentation of fundamental quarks and gluons that are collected within a cone of radius R, are of special interest since they develop on time-scales comparable to the lifetime of the plasma. Jet ``quenching'', or the suppression of the jet yield at large transverse momentum, is therefore a probe not only of the elastic and inelastic interactions with the medium, but also of the medium's capability to resolve correlated QCD color charges. The energy removed from the jet is redistributed in modes that span hard collinear gluon radiation (bremsstrahlung) to softer excitations that ultimately thermalize with the surrounding medium.

The radius dependence of the jet spectrum is particularly sensitive to the rich physics outlined above. In the first part of the talk, I will present a recent calculation of the jet spectrum in heavy-ion collisions where the medium parameters are sampled from a realistic hydrodynamic evolution of the QGP. Up to relatively large radii R~0.6, the suppression is dominated by perturbative physics while non-perturbative effects, related to the details of thermalization, start to dominate at R~1. This provides, for the first time, a solid basis for higher-order precision calculations of the jet spectrum that are paramount to realize the potential of hard probes as precision tools to extract the properties of the QGP.

However, jets are rare events and their spectrum drops rapidly with transverse momentum. This induces a strong bias on any process happening in the medium and makes it hard to dig out rare events where heavy-ion jets were substantially modified. In the second part of my talk, I will report on a recent attempt to extract the jet energy before quenching using machine learning. This allows to reduce the biases and enhance the signal of medium modifications. It also allows to better constrain jets as tomographic tools of the medium.

Slides

Recording (Link will become inactive 6 months after February 12, 2021)

February 5, 2021

Prof. Rainer J. Fries, Texas A&M University

Constraining the Effective Shear Viscosity of Hot Hadron Matter

Abstract

Transport properties of exotic QCD matter have received much attention since it was discovered that very low shear viscosity-over-entropy ratios eta/s are realized in quark gluon plasma just above the pseudo-critical temperature Tc that separates this phase from hot hadron matter. Both theoretical calculations and estimates from data collected in high-energy nuclear collisions have indicated values of eta/s close to the conjectured lower bound, implying that quark gluon plasma is an almost perfect liquid. Moving our attention below Tc, the transport properties of hot hadron matter are less clear. Theoretical predictions differ by an order of magnitude. We argue that constraints on hadronic eta/s can be derived from the same high-energy nuclear data sets, if the deviations of final freeze-out particle distributions from thermal equilibrium are analyzed. In this talk we describe our method, our attempts to quantify uncertainties, our final results, and the remaining open questions.

Slides

January 29, 2021

Dr. Aihong Tang, Brookhaven National Laboratory

Search for the Chiral Magnetic Effect in Heavy Ion Collisions: Challenges and Status

Abstract

The Chiral Magnetic Effect (CME) is the generation of electric current induced by local chirality-imbalance in the presence of magnetic field, and the existence of CME in relativistic heavy ion collisions is an indication of local parity violation in strong interactions. The experimental search for the CME has been carried out extensively in the past decade at the Relativistic Heavy Ion Collider and the Large Hadron Collider. In this talk, I will review the current progress of experimental studies of CME, with particular emphasize on the challenge associated with background separation, as well as special considerations on isobaric collisions.

Slides

January 22, 2021

Dr. Peter M. Jacobs, Lawrence Berkeley National Laboratory

Jet quenching at RHIC and LHC: a status report

Abstract

Jet quenching, the interaction of energetic jets with the Quark Gluon Plasma (QGP), was discovered 20 years ago. However, its underlying mechanisms, and what jet quenching measurements tell us about the QGP, are still only partly understood. There has been an explosion of new jet quenching observables and measurements in the past few years, whose connections and overall physics message are sometimes difficult to discern. I will suggest a framework to think about them in a unified way, and discuss selected measurements of inclusive jet suppression and in-medium jet scattering by STAR@RHIC and ALICE@LHC. I will also discuss prospects of a comprehensive understanding of jet quenching using the tools developed by the JETSCAPE Collaboration.

Slides

January 15, 2021

Prof. Scott Pratt, Michigan State University

Extracting the Diffusivity of Light Quarks in the Quark Gluon Plasma from Heavy-Ion Collisions

Abstract

The diffusivity and viscosity are the two most fundamental transport coefficients of the quark-gluon plasma. Whereas viscosity has attracted enormous attention, the diffusivity has garnered less attention because it has been seen as less experimentally accessible. In this talk, experimental measurements of correlations based on local charge conservation, especially those involving kaons, will be shown to be sensitive to the diffusivity. It will be demonstrated that with careful modeling and analysis the diffusivity might be extracted at the 50% or factor of 2 level, which is similar to the degree to which the shear viscosity has been constrained.
Fall 2020
December 11, 2020

Dr. Chun Shen, Wayne State University

Observable signatures of initial state momentum anisotropies in nuclear collisions

Abstract

We show that the correlation between the elliptic momentum anisotropy, v2, and the average transverse momentum, [pT ], at fixed multiplicity in nuclear collisions carries information on the origin of the observed momentum anisotropy. We develop the hybrid IP-Glasma+Music+UrQMD model that includes contributions from final state response to the initial geometry as well as initial state momentum anisotropies of the Color Glass Condensate. This model predicts a characteristic sign change of the correlator ρ_2(v2, [pT ]) as a function of charged particle multiplicity in p+Au and d+Au collisions at s = 200 GeV, and p+Pb collisions at s = 5.02 TeV. This sign change is absent in calculations without initial state momentum anisotropies. The model further predicts a qualitative difference between the centrality dependence of ρ_2(v2,[pT]) in Au+Au collisions at s = 200GeV and Pb+Pb collisions at s = 5.02TeV, with only the latter showing a sign change in peripheral events. Experimental observation of these distinct qualitative features of ρ_2(v2, [pT ]) in small and large systems would constitute strong evidence for the presence and importance of initial state momentum anisotropies predicted by the Color Glass Condensate effective theory.

December 4, 2020

Dr. Matthew Kelsey, University of Cincinnati

Heavy Flavor in Nuclear Science

Abstract

Measurements of hadrons containing heavy flavor quarks has emerged as one of the pillars of heavy-ion physics due to the nature of their production, which allows them to be treated as “external” probes of the de-confined medium produced in heavy-ion collisions. Their utility in probing the various stages of the heavy-ion collisions, spanning from the initial conditions to hadronization, has been exploited at both the Relativistic Heavy-Ion Collider (RHIC) and Large Hadron Collider (LHC), with some interesting results emerging in recent years. In this seminar I will give an experimental review of (open) heavy flavor hadron measurements in heavy-ion collisions, with a focus on recent results from the STAR collaboration which has extended the measurements into the bottom quark sector. Additionally, with the Electron-Ion Collider (EIC) emerging as the future US-based precision QCD machine set to supersede RHIC, I will highlight potential experimental opportunities with heavy flavor with a precision silicon-based vertex detector.

November 20, 2020

Dr. Elena Gramellini, Fermi National Accelerator Laboratory

The What, the Why and the How of Testbeam Experiments for Neutrinos

Abstract

As we enter the era of neutrino precision physics, the need arises for detectors with highly accurate response models, for full scale proto-types, and for a detailed understanding of the interplay between the products of neutrino interactions and the target nucleus. Testbeam experiments can provide all of that. This talk will present a (biased) overview of recent testbeam efforts for neutrino physics, focusing on experiments with high Fermilab involvement. By discussing a few selected examples, we will explore why and how testbeam experiments are key players in the current neutrino physics panorama.

November 13, 2020

Dr. Joachim Moritz Brod, University of Cincinnati

Precision Standard-Model Prediction of epsilon_K

Abstract

The parameter epsilon_K describes CP violation in the neutral kaon system and is one of the most sensitive probes of new physics. The large uncertainties related to the charm-quark contribution to epsilon_K have so far prevented a reliable standard-model prediction. In this talk, I will review mixing in the neutral kaon system, and then show that CKM unitarity suggests a unique form of the weak effective Hamiltonian in which the short-distance theory uncertainty of the imaginary part is dramatically reduced. The uncertainty related to the charm-quark contribution is now at the percent level. I will conclude with an outlook on further calculations that have the potential to render epsilon_K a precision observable on par with the rare kaon decays.

November 6, 2020

Dr. James Mulligan, Lawrence Berkeley National Laboratory, University of California-Berkeley

Simulating real-time dynamics of hard probes in nuclear matter on a quantum computer

Abstract

Recent advances in quantum devices have raised the prospect for widespread scientific applications of quantum computing within the next few years. We present a framework to simulate the real-time dynamics of hard probes such as heavy quarks or jets in a hot, strongly-coupled quark-gluon plasma (QGP) on a quantum computer. Hard probes in the QGP can be treated as open quantum systems, in which a subsystem interacts with an external environment. Due to large computational costs, most current phenomenological calculations of hard probes evolving in the QGP use semiclassical approximations of the quantum evolution. Quantum computation can mitigate these costs, and offers the potential for a fully quantum treatment with exponential speedup over classical techniques. We report a simplified demonstration of our framework on IBM Q quantum devices, and apply recently developed error mitigation techniques. Our work demonstrates the feasibility of simulating open quantum systems on current and near-term quantum devices, which is of broad relevance to applications in both hot and cold nuclear matter.

Slides

October 30, 2020

Dr. Robert Bernstein, Fermi National Accelerator Laboratory

Searching for muon to electron conversion: The Mu2e experiment at Fermilab

Abstract

The Mu2e experiment will measure the charged-lepton flavor violating (CLFV) neutrino-less conversion of a negative muon into an electron in the field of a nucleus. The conversion process results in a monochromatic electron with an energy slightly below the muon rest mass. Mu2e will improve the previous measurement by four orders of magnitude using a new technique, reaching a SES (single event sensitivity) of 3 x 10^{-17} on the conversion rate, and a discovery at 2 x 10^{-16}. The experiment will reach mass scales of nearly 10^4 TeV, far beyond the direct reach of colliders. The experiment is sensitive to a wide range of new physics, complementing and extending other CLFV searches. Mu2e is under design and construction at the Muon Campus of Fermilab with our first physics run in early 2025.

October 23, 2020

Dr. Linda Carpenter, Ohio State University

Indirect Detection in Next Generation Dark Matter Models

Abstract

Next Generation DM models go beyond simplified models to offer a full theoretical picture of the mediating particle between DM and the Standard Model. These models often have multiple mediating particles, and multiple coupling between Dark Matter and the Standard Model fields. As such indirect detection spectra are very complex. I introduce a new calculational tool to automatically compute all 2-2 DM annihilation process to and any and all gauge invariant pairs of SM particles, in generic user generated models. This tool computes and visualized the partial annihilation rates and photon flux spectrum, then compares the spectrum to known photon flux measurements to generate constraints on the Dark Sector.

October 16, 2020

Dr. David Curtin, University of Toronto

Cosmology and Astrophysics of Dark Complexity

Abstract

Dark matter could be part of a complex dark sector that is distinct from but in some ways analogous to the visible sector. This is motivated, for example, by the Twin Higgs model, which solves the little Hierarchy Problem without colored top partners, but also generically by analogy to the richness and non-minimality of the Standard Model. The Twin Higgs model provides a useful benchmark to explore the vast signature space of dark complexity in a theoretically motivated framework. Dark complexity is the flipside of hidden valleys phenomenology at colliders, and depending on model details, the phenomenology looks very different: either spectacular long-lived particle signals at colliders, or a plethora of unusual cosmological and astrophysical signatures via the existence of a predictive hidden sector. I will focus on the latter possibility, and describe how the asymmetrically reheated Twin Higgs realization of dark complexity predicts correlated signals in the CMB, Large Scale Structure, and direct detection searches, as well as higgs precision measurements at colliders. The existence of complex interacting DM relics also predicts highly exotic stellar objects called Mirror Stars with signatures that are remarkably robust with respect to theoretical uncertainties in the hidden sector. Mirror stars could be the first and highly spectacular harbinger of dark complexity and may show up in optical and X-ray searches, LIGO gravitational wave signals, or microlensing surveys. This provides a vivid, multidisciplinary example of the complementarity between collider experiments and cosmological/astrophysical observations to discover the solution to fundamental mysteries like dark matter and the hierarchy problem.

October 9, 2020

Dr. Brian Shuve, Harvey Mudd College

Baryogenesis and Dark Matter from Freeze-In

Abstract

I propose a simple, unified, and testable framework for the generation of the baryon asymmetry and dark matter. The baryon asymmetry and dark matter are created via freeze-in through the the decays and inverse decays of QCD-triplet scalars, at least one of which must be in the TeV mass range. I will show that the out-of-equilibrium baryogenesis condition and the dark matter density constraint typically require the lightest scalar to be long-lived, giving good prospects for detection or exclusion in current and upcoming colliders. I will also motivate other astrophysical, cosmological, and collider signatures.

October 2, 2020

Dr. Robert Schabinger, Michigan State University

Cusp and Collinear Anomalous Dimensions in Four-Loop QCD from Form Factors

Abstract

In this talk, I present a recent ab initio calculation of the four-loop cusp anomalous dimensions of massless QCD. Novel computational technology developed by us over the course of several years was critical to our success. Our methods and approach to the calculation open the door to the calculation of the four-loop collinear anomalous dimensions of massless QCD, for which we have already obtained precise numerical results superior to the estimates currently available in the literature.

September 18, 2020

Dr. Miguel Arratia, University of California-Riverside

Jet tomography of the proton at the future Electron-Ion Collider

Abstract

The future Electron-Ion Collider (EIC) will use electrons to image the quarks and gluons inside protons and neutrons with unprecedented precision. This will allow us to reveal the origin of their mass, spin, radius, and other properties. The EIC will not only allow us to extend traditional studies from fixed-target experiments to uncharted kinematic regions, but also will give us a novel tool: “jets” of particles. In this talk, I will focus on the prospects of using jets to perform a “quantum 3D tomography” of the proton at the EIC. I will discuss the experimental feasibility of key measurements that will exploit the unprecedented combination of hermetic tracking, particle identification, and calorimetry of the future EIC detectors. I will argue that a jet program at the EIC could unleash a new era in the field of 3D imaging of the nucleon.

September 11, 2020

Dr. Lia Corrales, University of Michigan

New Frontiers of X-ray Exploration: From Astromineralogy to Supermassive Black Holes

Abstract

X-ray astronomy as a field has only existed for about 60 years, yet has led to some of the most breathtaking discoveries in the last century of astrophysics. In this talk, I will discuss two science frontiers of high resolution X-ray imaging and spectroscopy: (1) the astromineralogy of interstellar dust grains, and (2) the accretion flow of Sgr A*, the supermassive black hole at the center of the Milky Way. The X-ray energy band is sensitive to absorption and emission by all abundant metals in the interstellar medium (ISM), both in gas and dust form, enabling us to answer key questions in dust grain growth and processing. X-ray photoabsorption features observed in high resolution spectra of Galactic X-ray binaries directly reveal the mineral composition of interstellar dust. I will review my work on the heavily obscured Galactic Center sight line, where dust scattering significantly alters the apparent size, spectral shape, and timing of X-ray variable sources. And finally, after 20 years of the Chandra X-ray Observatory, we have released new high resolution spectral data for Sgr A* that will be irreplaceable for the next 10-20 years. I will describe how future X-ray missions — XRISM, ARCUS, Athena, and Lynx — will contribute to each of these topics.

September 4, 2020

Dr. Prithwish Tribedy, Brookhaven National Laboratory

Status of CME Search Before Isobar Collisions and Methods of Blind Analysis From STAR

Abstract

The STAR collaboration is currently pursuing the blind analysis of the data for isobar collisions that was performed at RHIC in the year 2018 to make a decisive test of the Chiral Magnetic Effect (CME). Why is it so difficult to detect signals of CME in the experiment? Do we really understand different sources of background? Why observing similar charge separation between p/d + A and A + A does not stop us from pursuing the search for CME? In my talk, I‘ll attempt to address some of these questions and briefly outline a few recent STAR analyses based on new methods and observables to isolate the possible CME-driven signal and non-CME background contributions at the top RHIC energy. Finally, I describe the procedure for the blind analysis of the isobar data. An outstanding question remains – what happens if we go down in energy? I address this by discussing how the new event-plane detector (EPD) upgrade provides a new capability at STAR towards CME search using the data from the RHIC BES-II program.
Winter 2020
April 10, 2020

Prithwish Tribedy

April 3, 2020

Elena Gramellini

March 27, 2020

Dr. Lia Corrales

March 20, 2020

Dr. Malte Buschmann, University of Michigan

Foreground Mismodeling and the Point Source Explanation of the Fermi Galactic Center Excess

Abstract

The Fermi Large Area Telescope has observed an excess of ~GeV energy gamma rays from the center of the Milky Way, which may arise from near-thermal dark matter annihilation. Firmly establishing the dark matter origin for this excess is however complicated by challenges in modeling diffuse cosmic-ray foregrounds as well as unresolved astrophysical sources, such as millisecond pulsars. Non-Poissonian Template Fitting (NPTF) is one statistical technique that has previously been used to show that at least some fraction of the GeV excess is likely due to a population of dim point sources. These results were recently called into question, but we show that this is largely due to foreground mismodelling. We repeat the NPTF analyses using a state-of-the-art model for diffuse gamma-ray emission in the Milky Way and introduce a novel statistical procedure, based on spherical-harmonic marginalization, to provide an improved description of the Galactic diffuse emission in a data-driven fashion. With these improvements, we find that the NPTF results continue to robustly favor the interpretation that the Galactic Center excess is due, in part, to unresolved astrophysical point sources across the analysis variations that we have explored.

March 6, 2020

Dr. Spencer Klein, Lawrence Berkeley National Laboratory & University of California, Berkeley

Interactions of ultra-high energy cosmic neutrinos in IceCube

Abstract

The IceCube neutrino observatory has observed astrophysical neutrinos with energies up to 10 PeV (1 PeV = 10^15 eV)), 20,000 times higher in energy than are studied with particle accelerators. In addition to providing information about astrophysical particle accelerators, they allow us to extend studies of neutrino interactions by many orders of magnitude upward in energy. I will discuss our diffuse neutrino results and present two neutrino-properties measurements: a measurement of the neutrino interaction cross-section, determined by measuring neutrino absorption in the Earth, and a measurement of the inelasticity, the fraction of neutrino energy transferred to the outgoing lepton. I will also present a new technique: coherent radio Cherenkov emission from ultra-high energy neutrino showers, and plans to build a radio-array to instrument ~100 km^3 of Antarctic ice. A new detector extend neutrino studies up to 10^20 eV – beyond the energy reach of CERN’s Large Hadron Collider.

February 28, 2020

Dr. Yasuki Tachibana

Jet flowing in the quark-gluon plasma fluid

Abstract

We consider the case, in QCD, of a single jet propagating within a strongly interacting fluid, of finite extent. Interactions lead to the appearance of a source of energy-momentum within the fluid. The remnant jet that escapes the container is analyzed along with portions of the medium excited by the jet. We study the effect of a static versus an expanding medium, with jets traveling inward versus outward, considering the medium response via recoils in partonic scatterings based on a weakly-coupled description and its combination with hydrodynamical medium response based on a strongly-coupled description, followed by incorporation into a jet. The effect of these limits on the reconstructed energy, momentum and mass of the jet, as a function of the angle away from the original parton direction are studied. It is demonstrated that different flow velocity configurations in the medium produce considerable differences in jet observables. This work highlights the importance of accurate dynamical modeling of the soft medium as a foundation on which to calculate jet modification, and casts skepticism on results obtained without such modeling.

February 26, 2020

Dr. Dmitri Liventsev, KEK

Search for heavy neutrinos at Belle

Abstract

The Standard Model (SM) is very successful in explanating almost all experimental results but still fails to explain certain phenomena, namely baryon asymmetry of the Universe, existence of dark matter and neutrino oscillations. Heavy neutrinos appear in many extensions of the SM as a way to establish neutrino masses, provide a dark matter particle etc. We report on the search for heavy neutrinos using data collected by the Belle detector at the asymmetric e+e- collider KEKB in KEK, Tsukuba, Japan.

February 21, 2020

Florian Cougoulic, Ohio State University

Helicity-dependent generalization of the JIMWLK evolution

Abstract

The small-x evolution equations for the quark and gluon helicity distribution have recently been constructed by finding sub-eikonal corrections to the eikonal shock wave formalism. Those equations are written for correlators of infinite light-cone Wilson lines along with the so-called polarized Wilson lines. Those equations close in the large $N_c$-limit ($N_c$ is the number of quark colors), but also in the large $N_c & N_f$-limit ($N_f$ is the number of quark flavors). However, in the shock wave formalism, no closed form can be obtained for arbitrary value of $N_c$ and $N_f$.
For the unpolarized case, the generalization of the Balitsky-Kovchegov equation is done by the Jalilian-Marian—Iancu—McLerran—Weigert—Leonidov—Kovner (JIMWLK) functional evolution equation. Such an approach for the small-x evolution of the helicity is beneficial for numerical evaluation at finite $N_c$ and $N_f$ (beyond previously used limit), and for the evaluation of helicity-dependent operator with an arbitrary number of Wilson lines. We derive an analogue of the JIMWLK evolution equation for the small-x evolution of helicity distributions and obtain an evolution equation for the target weight functional.

February 7, 2020

Dr. Johannes Weber, Michigan State University

Strong coupling constant and heavy quark masses in (2+1)-flavor QCD

Abstract

I present three determinations of the strong coupling constant and one of the heavy quark masses in (2+1)-flavor QCD using lattice calculations with Highly Improved Staggered Quark (HISQ) action and extremely fine lattices. I discuss a determination using the moments of the pseudo-scalar quarkonium correlators at several values of the heavy valence quark mass and two complementary determinations of the strong coupling constant using the energy or singlet free energy of a static quark-antiquark pair at zero and finite temperature.

January 31, 2020

Matthew Luzum, University of São Paulo

Including momentum and stress in a systematic framework for describing the evolution of a heavy-ion collision

Abstract

The evolution of a relativistic heavy-ion collision is typically understood as a process that transmutes the initial geometry of the system into the final momentum distribution of observed hadrons, which can be described via a cumulant expansion of the initial distribution of energy density and is represented at leading order as the well-known eccentricity scaling of anisotropic flow.

We extend this framework to include the contribution from initial momentum-space properties, as encoded in other components of the energy-momentum tensor. We confirm the validity of the framework in state-of-the-art hydrodynamic simulations. With this new framework, it is possible to separate the effects of early-time dynamics from those of final-state evolution, even in the case when the distribution of energy does not fully determine subsequent evolution, as expected in small systems.

Specifically, we answer the question of when and how azimuthal correlations from the initial state survive to the final state. Additionally, this framework elucidates the generic features of the system evolution that are responsible for the impressive success of hydrodynamic simulations, but which may still hold even in cases when hydrodynamics is not applicable.

January 24, 2020

Dr. Nandita Raha, Wayne State University

The Muon g-2 xperiment at Fermilab

Abstract

The anomalous magnetic moment of the muon can be both measured and computed to a very high precision, making it a powerful probe to test the Standard Model and search for new physics. The previous measurement by the Brookhaven E821 experiment found a discrepancy from the SM predicted value of about ~3.6 standard deviations. The Muon g–2 experiment at Fermilab will improve the precision to 140 parts per billion compared to 540 parts per billion of E821 by increasing statistics and using upgraded apparatus. The first run of data taking has been accomplished in Fermilab, where the same level of statistics as E821 has already been attained. This talk/seminar, summarizes the basics of muon physics, the status of the experimental and briefly describes the data quality of the first run. It compares the statistics of this run with E821 and discusses the future outlook.
Fall 2019
November 15, 2019

Prof. Bhupal Dev, Washington University in St. Louis

Non-standard Neutrino Interactions

Abstract

In the Standard Model (SM), neutrinos can only interact via charged- and neutral-current weak processes. However, in beyond the SM scenarios for neutrino mass generation, the new mediators often induce non-standard interactions (NSI) of neutrinos with matter. Understanding these NSI effects is of great phenomenological interest, as they could probe the underlying neutrino mass mechanism, or at the very least, serve as a foil for the three-neutrino oscillation scheme. We will discuss a framework that could give rise to potentially observable NSI of either vector or scalar type, and their detection prospects at current and future experiments. In particular, we will discuss a new probe of NSI using the ultra-high energy neutrinos at IceCube.

November 8, 2019

Prof. Jure Zupan, University of Cincinnati

Anomaly free Froggatt-Nielsen models of flavor

Abstract

We introduce two anomaly free versions of Froggatt-Nielsen (FN) models, based on either G_FN=U(1)^3 or G_FN}=U(1) horizontal symmetries, that generate the SM quark and lepton flavor structures. The structure of these ``inverted'' FN models is motivated by the clockwork mechanism: the chiral fields, singlets under G_FN, are supplemented by chains of vector-like fermions charged under G_FN. Unlike the traditional FN models the hierarchy of quark and lepton masses is obtained as an expansion in M/phi, where M is the typical vector-like fermion mass, and phi the flavon vacuum expectation value. The models can be searched for through deviations in flavor observables such as K-Kbar mixing, mu to e conversion, etc., where the present bounds restrict the masses of vector-like fermions to be above O(10^7 GeV). If G_FN is gauged, the models can also be probed by searching for the flavorful Z' gauge bosons. In principle, the Z's can be very light, and can be searched for using precision flavor, astrophysics, and beam dump experiments.

October 18, 2019

Prof. Sean Couch, Michigan State University

Toward a Predictive Theory of Core-collapse Supernova Explosions

Abstract

Tremendous progress has been made recently in our theoretical understanding of massive stellar death. This has been enabled in large part by the advent of high-fidelity 3D simulations of the supernova mechanism. I will discuss the recent developments and our progress in building a predictive theory of massive stellar death. In particular, I will discuss the important roles that turbulence and realistic 3D stellar structure are playing in the supernova mechanism. I will also present the emerging picture of the very complex connection between progenitor structures and the outcomes of stellar core collapse. Finally, I will discuss the role of ubiquitous rotation and magnetic fields in altering the character of supernova explosions. All stars rotate and have magnetic fields and this fact can have a qualitative impact on core-collapse supernova explosions.

October 11, 2019

Mayank Singh, McGill University

Thermal fluctuations in relativistic heavy ion collisions

Abstract

Heavy ion collision experiments are appropriate systems for studying QCD at high energies. Owing to the extremely small sizes and lifetimes of these systems, we cannot use external probes to study these. Experiments typically detect the particles produced after these collisions. A standard phenomenological model is used to interpret the data from these experiments. A key component of the model uses relativistic hydrodynamics to simulate the evolution of a strongly interacting QGP.
The anisotropies observed in the experiment are usually attributed to the geometric and quantum fluctuations in the initial stages of the collisions. Thermal fluctuations in the QGP phase are another possible source of these fluctuations which have largely been excluded from theoretical studies owing to the technical difficulties in incorporating them. We present a procedure of including these fluctuations in simulations and quantying their effects on experimental observables.

October 4, 2019

Prof. David Cinabro, Wayne State University

Status of Belle II

Abstract

Belle II and SuperKEKB are the upgrades to the very successful Belle and KEKB B-factory. The goal of this new effort is to increase the data set by a factor of 50 enabling the search for physics beyond the standard model at the intensity frontier. Data taking started in early 2019, and I will describe the new detector and accelerator, give its present status, show some preliminary results, and estimate future prospects.

September 27, 2019

Deepa Thomas, University of Texas at Austin

Probing Quark-Gluon Plasma with heavy quarks

Abstract

Heavy quarks (charm and beauty) are powerful probes to investigate the production and properties of Quark-Gluon Plasma (QGP), a deconfined medium produced in high-energy heavy-ion collisions. Heavy quarks are produced in hard scattering processes with large momentum transfer before the formation of the QGP, thus experiencing the full evolution of the system. The partons transversing the QGP undergo energy loss by collisional and radiative processes. The dependence of these processes on the mass and color charge of partons can be studied with charm and beauty quarks. Studies of heavy-flavor angular correlations and jets allows characterization of the heavy-quark fragmentation processes. They can provide constraints to energy loss models adding information on how the energy is dissipated. In this talk, I will present experimental measurements of heavy-flavour production with the ALICE detector at the LHC, discuss what we have learnt from these results, and project future prospects.

September 13, 2019

Anthony Timmins, University of Houston

The structure of nucleus and proton at the LHC

Abstract

A variety of measurements from collisions of large and small systems are sensitive to the spatial configuration of the initial state of those systems. One important example is measurements of anisotropic flow, which carry information regarding the initial state eccentricity. To this end, I will review such measurements from the LHC running periods 1 and 2, and discuss their implications for state of the art initial state calculations. I will also discuss prospects for future running periods at the LHC, where much larger data samples will be collected, and a greater variety of nuclear species are expected to be collided.
Winter 2019
January 18, 2019

Yacine Mehtar-Tani, Brookhaven National Laboratory

Higher order corrections to jet quenching in heavy ion collisions

Abstract

In standard analytic approaches to energy loss in heavy ion collisions, jets are approximated by single partons and thus higher-order effects in the strong coupling constant are neglected. This may prove insufficient to reliably extract QGP properties at high pT, where a significant jet suppression was recently reported by the ATLAS collaboration in PbPb collisions at the LHC. In this work, we explore higher-order contributions to the inclusive jet spectrum which may be sizable owing to the fact that the probability for a highly virtual parton to split in the medium increases with the jet pT. As the effective number of jet constituents increases, jets are expected to lose more energy than a single color charge. This translates into a logarithmic enhancement of higher orders in the perturbative series that need to be resumed. As a result, we obtain a Sudakov-like suppression factor which we investigate in the leading logarithmic approximation. We note, however, that the phase space for higher-order corrections is mitigated by coherence effects that relate to the fact that, below a characteristic angular scale, the medium does not resolve the inner jet structure. In this case, the jet loses energy coherently as a single color charge, namely, the primary parton.

February 1, 2019

Jorge Noronha, Rutgers University

High-density matter out of equilibrium: from the lab to the sky

Abstract

In this seminar, I will discuss some of the main challenges concerning the description of quantum chromodynamics (QCD) in the baryon-rich regime in heavy-ion collisions and also in neutron star mergers. After presenting a realistic prediction for the location of the critical point in the QCD phase diagram, I will present the first systematic study of the emergence of hydrodynamics in a far-from-equilibrium relativistic fluid with a critical point. For rapidly expanding systems such as the matter formed in heavy-ion collisions, the onset of hydrodynamic behavior is shown to be significantly delayed by the presence of critical phenomena. We then switch gears to consider the out-of-equilibrium behavior of the extremely dense matter formed in neutron star mergers. We solved a long-standing open problem in the field of viscous hydrodynamics and its coupling to general relativity by proving causality, existence, and uniqueness of the solutions of the highly nonlinear equations of motion of viscous hydrodynamics in curved spacetime. These results pave the way for the inclusion of viscous effects in state-of-the-art simulations of gravitational-wave signals coming from neutron star mergers.

February 8, 2019

Elias Kammoun, University of Michigan

X-Ray obscuration in active galactic nuclei

Abstract

It is commonly thought that "type 2" active galactic nuclei (AGN) are usually obscured in X-rays by material with high column densities (NH), whose exact location and distribution remain an open question. The obscuring material is generally identified with dusty molecular "torus" at the parsec scale, within the "Unification Scenarios" of AGN. However, several pieces of evidence challenge this interpretation. In particular, a handful of AGN has shown rapid changes in column density that are in favor of a clumpy distribution of optically thick clouds rather than a homogeneous structure. The NH-variability timescale suggests that the material is located closer distances to the supermassive black hole (SMBH) which is consistent with the broad-line region (BLR). In this context, the passage of a BLR-gas cloud in our line of sight, that is orbiting the SMBH, will not affect only the AGN's light curve but it shows also a strong impact on its spectroscopic and polarimetric properties. In fact, as the cloud moves in our line of sight it will shade different regions of the accretion disc, which will allow us to probe the innermost regions close to the SMBH. In my talk, I will present the X-ray spectral and polarimetric effects of such eclipsing events. Then, I will present the first results from a survey carried with the Nuclear Spectroscopic Telescope Array (NuSTAR) that aims to characterize the hard X-ray properties of obscured AGN in the local Universe. I will also discuss the role that future high-resolution X-ray observatories such as Athena and XARM will play in identifying and studying obscured AGN.

March 1, 2019

Abigail Stevens, Michigan State University

Mapping Matter in Strong Gravity: Spectral-Timing of Black Holes and Neutron Stars

Abstract

One of the best laboratories to study strong-field gravity is the inner 100s of kilometers around black holes and neutron stars in binary systems with low-mass stars like our Sun. The light curves of low-mass X-ray binaries show variability on timescales from milliseconds to months — the shorter (sub-second) variability is particularly interesting because it probes the inner region of the accretion disk and compact object. My research looks at X-ray quasi-periodic oscillations (QPOs) from black holes and neutron stars (as well as coherent X-ray pulsations from neutron stars) by fitting the phase-resolved energy spectra of these signals to constrain their physical origin and track their evolution in time. In this talk, I will present a state-of-the-art "spectral-timing" analysis of QPOs from different classes of sources and different accretion states, and I will discuss how this sets the stage for future research.

April 5, 2019

Amber Stuver, Villanova University

May 8, 2019

Tapan Nayak

Characterizing the Quark-Gluon Plasma with the ALICE experiment at the CERN

Abstract

For only a few millionths of a second after the Big Bang, our universe consisted of a hot and dense soup of quarks and gluons, which cooled down very quickly to form protons, neutrons, and other such normal nuclear matter. The discovery and characterization of this new phase of matter called the quark-gluon plasma (QGP), required the creation of a sufficiently large and extended volume of hot and dense matter, which is possible by colliding heavy-ions at ultra-relativistic energies.

The Large Hadron Collider (LHC) at CERN, commissioned in the year 2009, has collided proton-proton, proton-lead, xenon-xenon and lead-lead ions at unprecedented energies. The ALICE (A Large Ion Collider Experiment) collaboration at the LHC has carried out a comprehensive study to characterize the QGP phase through various probes. In the presentation, we will discuss the recent results from ALICE and the future program at the LHC.

May 10, 2019

Luca Visinelli, Stockholm University

Probing the Early Universe with Axion Physics

Abstract

Axions and axion-like particles are excellent dark matter candidates, spanning a vast range of mass scales from the milli- and micro-eV for the QCD axion, to 10^-22eV for ultralight axions, to even lighter candidates that make up the “axiverse”. In some scenarios, inhomogeneities in the axion density lead to the formation of compact structures known as axion “miniclusters” and axion stars. Topological defects in the early universe might also contribute the energy density of axions and generate primordial gravitational waves that can possibly be detected in future experiments. I will first discuss astrophysical and cosmological constraints on axions at either end of this spectrum, using data from the cosmic microwave background anisotropies and the effects of miniclusters on the gravitational microlensing and on direct detection. I will then assess the formation and the evolution of axion stars in various astrophysical regimes.
Fall 2018
September 14, 2018

Joe Osborne, University of Michigan

Effects from color flow in proton-proton and proton-nucleus collisions

Abstract

In the last two decades, the study of nucleon structure has shifted from a one-dimensional picture to exploring the dynamic three-dimensional structure of partons within the nucleon. In the transverse-momentum-dependent framework, non-perturbative parton distribution functions and fragmentation functions explicitly carry dependence on partonic transverse momentum rather than only the collinear momentum of the parton with respect to the hadron. The recent interest in the transverse structure of the proton has largely been motivated by the novel phenomenological consequences that have been predicted for these nonperturbative functions, in particular regarding the role that color charge plays in hard scattering processes. For example, factorization breaking has been predicted in hadronic collisions where a final-state hadron is measured and the observable is sensitive to nonperturbative transverse momentum. This prediction has the interesting quantum mechanical consequence that partons are entangled via their color across colliding protons. In this talk, I will discuss the role of color flow in addition to recent results sensitive to these predicted effects in proton-proton and proton-nucleus collisions.

September 28, 2018

Gojko Vujanovic, Ohio State University

Understanding the QGP through the lens of electromagnetic radiation

Abstract

Recent viscous hydrodynamical studies [1,2] at the Relativistic Heavy-Ion Collider (RHIC) and the Large Hadron Collider (LHC), show that bulk viscosity plays an important role in their phenomenological description. A temperature-dependent bulk viscosity in the hydrodynamical evolution of the medium can modify the development of the hydrodynamic momentum anisotropy differently in the high- and low-temperature regions. Thus, anisotropic flow coefficients of various observables are affected differently depending where their surface of last scattering lies. For the case of hadronic observables, they are predominantly sensitive to low-temperature regions, while electromagnetic radiation is emitted at all temperatures. Therefore, bulk viscosity should affect electromagnetic radiation differently than hadron emission. The effects of bulk viscosity on one of the electromagnetic probes, namely photons, has already been investigated [1]. The same statement holds true for hadrons [2]. The goal of this presentation is to study how thermal dilepton production, the other source of electromagnetic radiation, gets modified owing to the presence of bulk viscosity at RHIC and LHC energies. With calculations at different collision energies, comparisons in the dilepton signal can be made and more robust conclusions regarding the role of bulk viscosity in high energy heavy-ion collisions can be drawn. Dilepton radiation from the dilute hadronic phase of the medium will also be included to ascertain whether these modifications may be observable in experimental data. [1] Jean-François Paquet et al., Phys. Rev. C 93 no. 4, 044906 (2016) [2] S. Ryu et al., Phys. Rev. Lett. 115 no. 13, 132301(2015).

October 5, 2018

Joshua Berger, University of Pittsburgh

Abstract

Detecting boosted dark matter at large volume neutrino detectors

We study novel scenarios where thermal dark matter (DM) can be efficiently captured in the Sun and annihilate into boosted dark matter. In models with semi-annihilating DM, where DM has a non-minimal stabilization symmetry, or in models with a multi-component DM sector, the annihilation of DM can give rise to stable dark sector particles with moderate Lorentz boosts. Taking advantage of the energetic proton recoils that arise when the boosted DM scatters off matter, we propose a detection strategy that uses large volume terrestrial detectors, such as those designed to detect neutrinos or proton decays. In particular, we propose a search for proton tracks pointing away from the Sun. We present bounds and sensitivity at Super-Kamikande and Hyper-Kamiokande respectively. We then discuss the possibilities for enhanced sensitivity at DUNE and other liquid argon TPC detectors. We present the first full Monte Carlo event generation for boosted dark matter and discuss the modeling challenges. We use this tool to discuss the first fully realized analysis of boosted dark matter at DUNE.

October 9, 2018

Jake Bennett, University of Mississippi

First collisions and plans for the future at Belle II

Abstract

The Belle II experiment, currently under construction at the KEK laboratory in Tsukuba, Japan, is the next generation of the highly successful B-factories. A substantial upgrade of both the Belle detector and the KEKB accelerator represent an essentially new experiment. The ultimate goal of Belle II is to collect about 50 times as much data as its predecessor, opening the path to measuring rare decays that may give hints on the hunt for new physics. Commissioning of the accelerator was recently completed and preparations are ongoing for data taking with the full Belle II detector in the spring of 2019. With this early data, it is possible to start getting an idea of the expected performance of the detector as well as to better understand beam backgrounds. In this talk, I will introduce the experiment and present some of the first results coming from Belle II.

October 19, 2018

Chun Shen, WSU

Dynamical modeling of relativistic heavy-ion collision: correlations from flows and beyond

Abstract

In this talk, I will discuss that the universal hydrodynamic response can lead to a consistent description of the flow observables in heavy-ion collisions over more than 2 orders of magnitude in measured hadron multiplicity. This standard theoretical framework helps us to elucidate the origin of the collective behavior in small collision systems, such as high multiplicity p+Pb collisions. Next, by going beyond the long-range flow correlations, we implement local charge conservation during the particlization stage. It introduces non-trivial short-range correlations. A first study gives promising results compared to the Au+Au measurements at the top RHIC energy. This can provide the most realistic background calculations for the RHIC isobar runs for the search of the Chiral Magnetic Effects.

October 26, 2018

Luke Pickering, University of Michigan

Neutrino interactions: Effects on T2K oscillation analyses

Abstract

Neutrino oscillation experiments are chasing the answer to a number of fundamental questions, most importantly: Is there enough Charge-Parity violation in the lepton sector to explain the deficit of anti-matter in the observable universe? In the 1–5 GeV neutrino energy region—where current and planned accelerator-based beams peak—neutrino–matter interaction theory is non-perturbative, and currently available models fail to predict the extant data well. This is problematic for oscillation analyses that depend strongly on interpreting observations through such models. Over the next decade, interaction-model uncertainties will set the limit on the precision of oscillation experiments. The Tokai-to-Kamioka (T2K) experiment, which has been taking data since 2010, is one such oscillation experiment. The latest analysis shows tantalizing hints of differences in the oscillation of neutrinos and antineutrinos—i.e. lepton sector CP violation. This talk will discuss what we are currently learning with the T2K data, how the neutrino interaction uncertainties are parameterized, and what the future holds for the field.

November 2, 2018

Malte Buschmann, University of Michigan

Simulation of a cosmological axion through the QCD phase transition

Abstract

We perform a full (3+1)-dimensional numerical simulation of the axion field around the QCD epoch.
Our aim is to fully resolve large dynamical non-linear effects in the inhomogenous axion field. These effects are important as they lead to large overdensities in the field at late times. Those overdensities will eventually evolve into an axion mini-cluster, which has various phenomenological implications like microlensing events. It is therefore important to have a reliable estimate of the number of overdensities and their mass relation.

November 9, 2018

Felix Ringer, LBNL

Jet substructure in high-energy hadron collisions

Abstract

Collimated jets of hadrons serve as precision tests of the standard model and in particular QCD. For example, inclusive jet and jet substructure observables have been applied extensively to constrain Parton distribution functions and to probe the hot and dense medium created in heavy-ion collisions, as well as to the search for physics beyond the standard model. In this talk, I will mainly focus on recent theoretical developments based on the effective field theory approach to jet physics. This newly established framework allows for precision calculations of jet cross-sections and enables a direct comparison of experimental data and first-principles calculations of jet substructure observables. In addition, I will discuss a new approach to QCD factorization of jet cross-sections in heavy-ion collisions.

November 16, 2018

Takafuni Niida, WSU

Vorticity and polarization in heavy-ion collisions

Abstract

The matter created in non-central heavy-ion collisions is expected to possess a significant fraction of the initial angular momentum carried by the two colliding nuclei. This angular momentum can lead to vorticity of the system and be partially transferred to the spin of produced particles due to the spin-orbit coupling, leading to the phenomenon of global polarization. The STAR Collaboration observed finite signals in Au+Au collisions at √sNN = 7.7 - 39 GeV and later at √sNN = 200 GeV, indicating non-zero vorticity of the system. The global polarization might differ between particles and antiparticles, due to the opposite sign of the magnetic moments, which could be a direct tool to study the magnetic field in heavy-ion collisions. Furthermore, a possible local vortical structure along the beam direction might be caused by azimuthal anisotropic flow. In this talk, I will present recent results on the polarizations of Λ hyperons in heavy-ion collisions.

November 30, 2018

Rebecca Coles, Ohio State University

DESI commissioning instrument and metrology

Abstract

The Dark Energy Spectroscopic Instrument (DESI) is under construction to measure the expansion history of the Universe using the Baryon Acoustic Oscillation technique. The spectra of 35 million galaxies and quasars over 14000 sq deg will be measured during the life of the experiment. A new prime focus corrector for the KPNO Mayall telescope will deliver light to 5000 fiber optic positioners. The fibers, in turn, feed ten broad-band spectrographs. We will describe the methods and results for the commissioning instrument and metrology program, the products of which will be used to determine absolute astrometric reference data for subsequent telescope commissioning. We will use the commissioning instrument and metrology program to measure the absolute three-axis Cartesian coordinates of the optical devices on the commissioning instrument which will be needed to ensure that we accurately map the DESI correctors optical distortions.

December 7, 2018

Francis Halzen, Wisconsin IceCube Particle Astrophysics Center and Department of Physics, University of Wisconsin-Madison

IceCube: Beyond Astronomy

Abstract

An informal seminar on the other physics done with IceCube.

This special seminar is a follow-up to Professor Halzen's colloquium on Thursday, December 6, 2018.

December 7, 2018

Chris Monahan, Institute of Nuclear Theory

Semileptonic decays of B mesons from lattice QCD

Abstract

Where is all the new physics hiding? In spite of enormous successes, such as the discovery of the Higgs boson, and a mountain of data, direct searches at the LHC--the energy frontier--have so far failed to turn up new fundamental particles. An alternative approach is to hunt for answers at the intensity frontier: the possibility of new physics lurks in tantalizing discrepancies between theoretical predictions and experimental observations in the flavor physics sector. The Cabibbo-Kobayashi-Maskawa (CKM) matrix, which describes the mixing of quark mass eigenstates under the weak force, is unitary in the Standard Model. By constraining CKM matrix parameters through measurements of multiple different processes, any observations of deviations from unitarity may hint at new physics effects. Key to this program is precise theoretical predictions, which require lattice QCD calculations of hadronic contributions to Standard Model processes. I review the latest lattice calculations of B-meson decays from the HPQCD collaboration and highlight the role of results from LHCb, which are expected in the near future.

Particle-Astro-Nuclear (PAN) Physics seminars

Series archives

May 14, 2024

Randa Asad, American University of Sharjah

Ages, metalicities and detailed abundances of star clusters from their resolved and unresolved spect

Abstract

April 19, 2024

Joshua Spitz, University of Michigan

Using Ancient Rocks to Look for Atmospheric Neutrinos

Abstract

April 12, 2024

Junjie Zhu, University of Michigan

Latest diboson polarization results from ATLAS

Abstract

April 5, 2024

Jonathon Crass, Ohio State University

iLocater: Searching for Earth-like exoplanets among the stellar noise

Abstract

March 29, 2024

Filomena Nunes, Michigan State University

BAR: Bayesian Analyses of Reactions

Abstract

March 22, 2024

Mesut Arslandok, Yale University

Unveiling hadronization processes new insights and future perspectives with ALICE at LHC

Abstract

March 8, 2024

Angelo Ricarte, Harvard University

Event Horizon Insights Into the Cosmic Assembly of Supermassive Black Holes

Abstract

March 1, 2024

Malu Sudha, Wayne State

A Broadband Spectro-Temporal View of NS LMXBs

Abstract

February 23, 2024

Alakadha Datta, University of Mississippi

A sterile neutrino behind the B and MiniBooNE anomalies

Abstract

February 16, 2024

Friederike Bock, Oak Ridge

A New Era of Electron-Ion Collider Physics - The ePIC detector and its forward calorimeter

Abstract

February 9, 2024

Zhong Yang, CCNU

Quark-gluon plasma and jet-induced medium response in high-energy heavy-ion collisions

Abstract

February 2, 2024

Labani Mallick, University of Manitoba and CITA, University of Toronto

Impact of AGN on Black Hole’s Event Horizon, Host Galaxy, and Beyond

Abstract

January 26, 2024

Sandeep Chatterjee, IISER Berhampur

Deposition and evolution of baryons in relativistic heavy ion collisions

Abstract

January 19, 2024

Hendrik Roch, Wayne State University

Hybrid Hadronization and Fragmentation Hadrons in the Afterburner within the JETSCAPE Framework

Abstract

December 8, 2023

Cliff Burgess, McMaster University, Hamilton, ON

Open EFTs: A Decoherent Description of Primordial Fluctuations (special time)

Abstract

December 1, 2023

Gregoire Pihan , Wayne State University, Detroit, MI

Tracing the baryon number in relativistic isobar collisions at RHIC

Abstract

November 17, 2023

Christopher Madrid, FNAL

Harnessing Time: The CMS MIP Timing Detector for the HL-LHC Era

Abstract

November 3, 2023

Yang-Ting Chien, Georgia State University, Atlanta, GA

Open Target jet substructure and correlation

Abstract

October 27, 2023

Andrew Olivier, University of Norte Dame, Norte Dame, IN

Neutron Detection at the MINERvA Neutrino Scattering Experiment

Abstract

October 20, 2023

Ouynh Lan Nguyen, University of Norte Dame, Norte Dame, IN