Particle-Astro-Nuclear (PAN) Physics Seminar archive

Winter 2020

January 31

Matthew Luzum, University of São Paulo

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

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.

February 7

Dr. Johannes Weber, Michigan State University

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

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.

February 21

Florian Cougoulic, The Ohio State University

Helicity-dependent generalization of the JIMWLK evolution

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 an arbitrary value of $N_c$ and $N_f$.

For the unpolarized case, the generalization of the Balitsky-Kovchegov equation is done by the Jalilian-MarianIancuMcLerranWeigertLeonidovKovner (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 the previously used limit), and for the evaluation of helicity-dependent operator with an arbitrary number of Wilson lines. We derive an analog of the JIMWLK evolution equation for the small-x evolution of helicity distributions and obtain an evolution equation for the target weight functional.

February 26

Dr. Dmitri Liventsev (KEK)

Search for heavy neutrinos at Belle

The Standard Model (SM) is very successful in explaining almost all experimental results but still fails to explain certain phenomena, namely baryon asymmetry of the universe, the 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 28

Dr. Yasuki Tachibana

Jet flowing in the quark-gluon plasma fluid

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.

Fall 2019

September 27

Deepa Thomas, University of Texas at Austin

Probing Quark-Gluon Plasma with heavy quarks

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 allow 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 learned from these results, and project future prospects.

October 4

David Cinabro, Wayne State University

Status of Belle II

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.

October 11

Mayank Singh, McGill University

Thermal fluctuations in relativistic heavy-ion collisions

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 quantifying their effects on experimental observables.

October 18

Prof. Sean Couch, Michigan State University

Toward a Predictive Theory of Core-collapse Supernova Explosions

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.

November 8

Jure Zupan, University of Cincinnati

Anomaly free Froggatt-Nielsen models of flavor

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.

November 15

Prof. Bhupal Dev, Washington University in St. Louis

Non-standard Neutrino Interactions

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.

Winter 2019

January 18

Jorge Noronha, Rutgers University

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

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 1

Joe Osborne, Department of Physics, University of Michigan

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

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.

February 8

Elias Kammoun, University of Michigan

X-Ray obscuration in active galactic nuclei

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

Abigail Stevens, Michigan State University

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

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.

Fall 2018

September 14

Joe Osborne, Department of Physics, University of Michigan

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

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

Gojko Vujanovic, Ohio State University

Understanding the QGP through the lens of electromagnetic radiation

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

Joshua Berger, University of Pittsburgh

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

Jake Bennett, University of Mississippi

First collisions and plans for the future at Belle II

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 represents 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

Chun Shen, Wayne State University

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

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

Luke Pickering, University of Michigan

Neutrino interactions: Effects on T2K oscillation analyses

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 15 GeV neutrino energy regionwhere current and planned accelerator-based beams peakneutrinomatter 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 antineutrinosi.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

Malte Buschmann, University of Michigan

Simulation of a cosmological axion through the QCD phase transition

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 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

Felix Ringer, LBNL

Jet substructure in high-energy hadron collisions

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

Takafuni Niida, Wayne State University

Vorticity and polarization in heavy-ion collisions

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 Î' hyperons in heavy-ion collisions.

November 30

Rebecca Coles, Ohio State University

DESI commissioning instrument and metrology

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

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

IceCube: Beyond Astronomy

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

Chris Monahan, Institute of Nuclear Theory

Semileptonic decays of B mesons from lattice QCD

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 are 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.

Winter 2018

February 2

Kurt Jung, UIC

New Opportunities in Jet Measurements of the Quark-Gluon Plasma

In the current age of "Big Data" where the LHC reliably churns out tens of billions of collision events during each heavy-ion run period, our ability to probe the QGP with more rare objects is dramatically improving. This data overload, however, comes with a price, as it becomes more complicated to digest the onslaught of recent results in the context of how they relate to the QGP, especially with regard to recent measurements that suggest somewhat counterintuitive interpretations of small colliding systems. Recent measurements of azimuthal anisotropies in proton-lead collisions at the LHC show similar magnitudes to their lead-lead counterparts, suggesting a similar coherent behavior in both systems. This unexpected behavior, however, is tempered somewhat by the lack of any large jet modification effects in small systems. Finally, new measurements of jet substructure allow for new measurements of jet behavior in the medium independent of fragmentation, opening the door to highly-sensitive measurements of particle coherence in the medium. I will attempt to put these measurements in context and ask where we go from here.

February 16

Jinfeng Liao, University of Indiana

Strongly Interacting Matter Under Rotation

Recently the STAR Collaboration discovered the "subatomic swirls", that is, the most vortical fluid flow structures in the quark-gluon plasma produced via the AuAu collisions at the Relativistic Heavy Ion Collider (RHIC). Published in Nature and featured as a cover story, this discovery attracted significant interest and generated wide enthusiasm. In this talk, we discuss a number of progress in the theoretical studies of such strongly interacting matter under rotation, including novel effects from rotation on thermodynamics and phase transitions as well as transport processes. We also report quantitative studies of the vorticity structures in the QGP fluid from the transport model, and compute the global polarization effect of produced hadrons. In particular, our calculations show that the fluid vorticity in the CuCu or CuAu collision is comparable to that in the AuAu Collision. Surprisingly, we find the computed Î' hyperon polarization effect is enhanced in the CuCu and CuAu systems than the AuAu system at the same collisional beam energy and centrality class, with an interesting hierarchy CuCu > CuAu > AuAu due to interplay between Î' production timing and the time evolution of the vorticity. These predictions can be readily tested by experimental data.

February 23

Andrew Whitbeck, FermiLab

Observing the invisible: missing energy/momentum signatures at colliders & their implications for new physics

Understanding the hierarchy problem and elucidating the non-gravitational interactions of dark matter motivates collider searches for new physics with missing energy/momentum signatures. At the LHC, WIMPs are actively being searched for in the context of the Supersymmetric extensions to the SM (SUSY) which predict new sources of multijet plus missing energy events. New results in searches for R-parity conserving SUSY from CMS using 36/fb of 13 TeV data from the 2016 LHC run will be discussed. While these results are an important contribution to searches within the canonical WIMP parameter space, a new class of experiments is needed to probe thermal dark matter with masses less than ~1 GeV. Experimental challenges of fixed target experiments looking for invisible decays of dark photons, the prospect of applying CMS detector technology to address these challenges, and projected sensitivities of the LDMX experiment will be discussed.

March 1

Thomas Mehen, Duke University

Quarkonium Production in Jets at LHCb

This talk will describe new tests of quarkonium production using quarkonia that are produced within jets. We study the distribution in the fraction, z, of a jet's longitudinal momentum carried by the quarkonium. The z distribution is sensitive to the underlying NRQCD production mechanism. Analytic calculations of the z distributions in SCET that incorporate Next-to-Leading-Log (NLL) resummation disagree with default PYTHIA predictions. We describe a modified simulation method which agrees well with NLL analytic calculations. This method is then successfully applied to recent LHCb measurements of J/ψ within jets. We discuss the implications of this measurement for extractions of NRQCD long-distance matrix elements. Finally, we discuss other observables involving quarkonium within jets which may be useful for discriminating between NRQCD production mechanisms.

March 9

Sebastian Baum, Stockholm University

Dilute and Dense Axion Stars

Axion stars are hypothetical objects formed of axions, obtained as localized and coherently oscillating solutions to their classical equation of motion. Depending on the value of the field amplitude at the core |θ0|≡|θ(r=0)| , the equilibrium of the system arises from the balance of the kinetic pressure and either self-gravity or axion self-interactions. Starting from a general relativistic framework, we obtain the set of equations describing the configuration of the axion star, which we solve as a function of |θ0| . For small |θ0|?1 , we reproduce results previously obtained in the literature, and we provide arguments for the stability of such configurations in terms of first principles. We compare qualitative analytical results with a numerical calculation. For large amplitudes |θ0|?1 , the axion field probes the full non-harmonic QCD chiral potential and the axion star enters the dense branch. Our numerical solutions show that in this latter regime the axions are relativistic and that one should not use a single frequency approximation, as previously applied in the literature. We employ a multi-harmonic expansion to solve the relativistic equation for the axion field in the star, and demonstrate that higher modes cannot be neglected in the dense regime. We interpret the solutions in the dense regime as pseudo-breathers, and show that the lifetime of such configurations is much smaller than any cosmological time scale.

March 15

Daniel Pablos McGill University

Holography and The Problem of Parton Energy Loss in a Quark-gluon Plasma

The nearly perfect fluidity of the quark-gluon plasma (QGP) and its apparent strongly coupled nature has opened a rich window of phenomenology for holographic techniques. These studies offer key benchmarks against which to interpret the data in the context of the long-term quest towards the determination of the nature of the QGP degrees of freedom at collider relevant temperatures. In particular, the phenomenon of jet quenching, or parton energy loss, can be modelled through hybrid frameworks that exploit the wide separation of scales present in the system, combining perturbative QCD methods and holographic insights at their corresponding regime of applicability. In this talk, I will present the basis and phenomenology of such models, which are already capable of giving not only qualitative but also a quantitative description of many experimental data produced at the LHC and RHIC. Indeed, by exploring the geometric intuitions provided by holography, we are able to address genuine non-perturbative aspects of many body QCD that will hopefully lead us to a better understanding of the emerging collective behaviour observed in experiments (also in small systems), a crucial task in which the phenomenology of the jet/plasma interplay plays a central role due to its potential to unravel the precise way in which energy and momentum hydrodynamize in such short time scales.

March 23

Ryoutaro Watanabe, University of Montreal

Does complete set of data still prefer the B anomalies?

In this talk, I will show my ongoing work regarding new physics to accommodate the anomalies in b -> s mu mu and b -> c tau nu which have been standing on these days. So far, there are many papers for this topic and they concluded that U1 (singlet vector type of) leptoquark could explain the two simultaneously. In our work, we put a complete set of observables relevant for the above explanation and gives a fit analysis. As a result, we see what kind of patterns of LQ couplings are favored, which could be a guideline when one constructs a UV-completed model to accommodate the B anomalies.

March 30

Tyce DeYoung, MSU

First light at the IceCube Neutrino Observatory

The IceCube Neutrino Observatory, the world's largest neutrino detector, monitors a cubic kilometer of glacial ice below the South Pole Station to search for very high energy neutrinos from the astrophysical accelerators of cosmic rays. Since its commissioning in 2011, IceCube has discovered a flux of TeV-PeV scale astrophysical neutrinos, at a level with significant implications for our understanding of the dynamics of the non-thermal universe. The sources of this flux have remained elusive, however. In the last six months, hints of the identity of at least some of these sources have begun to emerge, suggesting that we are on the verge of opening a new window on the universe.

April 6

Jordan Steckloff, Planetary Science Institute

Breaking the Ice: How Sublimative Torques Alter and Destroy Cometary Bodies

To quote David Levy: "comets are like cats: they have tails, and they do precisely what they want." Comets are small ice-rich solar system objects that sublimate vigorously near perihelion. These sublimating gases entrain fine dust grains as they escape, forming a gas and dust cloud that can be seen from the Earth. Recent spacecraft missions to comets have found that that have strange bilobate shapes, undergo outbursts (rapid, unpredictable brightening events), and form long striated dust features in their tails that somehow align with the Sun rather than the nucleus. Additionally, their dynamics appear to require some mysterious mechanism for activating their sublimative activity. In this talk, I describe how all of these features are the result of ice sublimation, the process that defines these irregularly shaped bodies. Comets are too small to retain a significant atmosphere. Thus, the escaping, rarefied sublimating gases are asymmetrically distributed about the nucleus. This asymmetric sublimative mass loss generates torques that change the rotation state of the nucleus. Such rotational spin-up can induce internal stresses that fission the nucleus, forming cometary striae and preserving the strange bilobate shape of 67P/Churyumov-Gerasimenko. Additionally, the concentration of activity at the small lobe of 103P/Hartley 2 (and the activation/reactivation of comet nuclei more generally) is likely the result of avalanches triggered by such changes in the rotation state of the comet nucleus. Such avalanches may also cause highly collimated outburst plumes, such as those observed at 67P/Churyumov-Gerasimenko, which have thus far evaded explanation.

April 13

Keri Voss, Siegen University

Reparametrization of the heavy-quark expansion

The heavy-quark expansion has become an indispensable tool in the study of inclusive B decays. The heavy-quark expansion introduces a velocity vector v and allows for an expansion in the residual momentum of the heavy quark. The final result, however, is independent of the the choice of v and should be reparametrization invariance (RPI). In fact, RPI relates different orders in the heavy-quark expansion as was realized already years ago. We discuss the total rates of inclusive decays and obtain results that are manifestly RPI and can be expressed in terms of full QDC matrix elements and states. This approach leads to a partial re-summation the tower of operators of the heavy-quark expansion, which has the advantage that the number of independent parameters is reduced significantly.

April 20

Hsin-Yu Chen, Harvard University

Here comes the light GW170817 and gravitational-wave precision cosmology

With the first and second observing runs of Advanced LIGO and Virgo, the era of gravitational-wave astronomy has begun. One of the great promises of the field is the use of gravitational waves to directly measure the luminosity distance to sources, which was dramatically exemplified with the measurement of Hubble constant. In this talk I will share the discovery story of GW170817 and in particular discuss the constraints on the Hubble constant to be expected from binary mergers in ground-based gravitational wave detectors.

Fall 2017

August 7

Paul Moch Siegen University Loop-induced lepton and quark dipole transitions in Randall-Sundrum models We study the decay $mu to egamma$, $mu to 3e$, $mu N to e N$ as well as $tauto mugamma$, $tau to 3mu$ as well as $bar Bto X_s gamma$ in Randall-Sundrum models with an IR-localised bulk Higgs. The two models under consideration are a minimal model as well as a model with a custodial protection mechanism. We include the effects of treeand one-loop diagrams involving 5D gluon and Higgs exchanges as well as QCD corrections arising from the evolution from the Kaluza-Klein scale to the typical scale of the decay $bar Bto X_s gamma$.

August 14

Stefan Vogl, MPI

Dark Matter and the LHC: Realistic simplified models for collider searches

Dark matter searches at the LHC provide an intriguing way to probe dark matter interactions with the Standard Model. In order to allow for a flexible and reliable interpretation of LHC data and to facilitate comparison with other observables the "simplified model" framework, which is widely used by the experimental collaborations, has been developed. However, the simplified models used to describe the interactions of dark matter with Standard Model particles suffers from a number of shortcomings which limits their reliability. I'll discuss ways to address these issues and comment on the consequence for dark matter phenomenology.

September 8

Tan Luo, Central China Normal University

Linear Boltzmann Transport for Jet Propagation in the Quark Gluon Plasma

We develop a Linear Boltzmann Transport model for jet propagation in quark-gluon plasma in high-energy heavy-ion collisions. In this model, we take special consideration of recoiled partons from both elastic scattering and induced gluon radiation processes and their further propagation. Our simulations can provide description of not only the medium modification of the reconstructed jets but also the jet-induced medium excitation in the underlying hydrodynamic background. In this talk, we will discuss various jet observables in single jet and gamma-jets events and compare our results with the experimental data. To study the jet-medium interaction in detail, we further use the Linear Boltzmann Transport model (LBT model) coupled to (3+1)D ideal hydrodynamic evolution in real time with fluctuating initial conditions to simulate both the transport of jet shower partons and jet-induced medium excitation. In this coupled approach, soft partons from medium recoil and induced radiation from propagation of energetic shower partons in the Linear Boltzmann transport (LBT) model provide a source term to the 3+1D hydrodynamic evolution of the medium, which in term provide medium profile in real time for the parton shower propagation. With this coupled approach we investigate gamma-hadron correlations to study the effect of both jet-induced medium excitations and jet quenching due to parton energy loss.

September 15

Víctor Gonzalez, Universidad Complutense de Madrid

Determination of η/s with pT correlations from Pb-Pb collisions at √sNN = 2.76 and 5.04 TeV

QGP existence and its production in heavy ion collisions have been confirmed by experiments at RHIC and at LHC. The observed QGP behaves like a strongly interacting fluid that undergoes an explosive expansion, featuring a very low shear viscosity to entropy density ratio, η/s, i.e. exhibiting strong collectivity, but with near perfect liquid fluidity. Experimentally, the determination of the shear viscosity is conventionally carried out by comparing flow-coefficients, with predictions of hydrodynamical simulations involving shear viscosity to entropy density. Such comparisons feature many sources of theoretical uncertainty: initial conditions, event-by-event fluctuations, etc, but have been steadily improving making a 10% precision estimate of η/s now reachable. In the line of possible methods to determine η/s directly from measured data, a new theoretical approach, based on two-particle transverse momentum correlation, G2, was proposed by Gavin et al. The method relies on the existence of friction forces between neighboring fluid cells determined by the fluid viscosity. Friction produces drag that broaden the correlation function of particle pairs. The model of Gavin et al. is based on correlations between momentum currents which, experimentally, are measured with pT pair correlator G2. The challenge of obtaining η/s from LHC data at sNN = 2.76 and 5.04 TeV energies, within the reachable precision, will not only validate the proposed method but pave the way for extensions which will enable the extraction of the system relaxation time Ï"Ï€ from the evolution of the G2 rapidity profile showing the transition from a wavelike transport scenario to a diffusive one. This type of analyses, which extract results from the shape variation of, in this case, two-particle transverse momentum correlation, through different collision centralities, are very challenging, specially at the addressed energies. All the detector effects have to be identified and their impact minimized. But also the different pile-up scenarios, facilitated by the diverse time response of the involved detector components, have to be addressed and the potentially involved events discarded. We report on our progress in extracting η/s from LHC data at the ALICE detector as well as on the methods we are devising to cope with the detector inefficiencies.

September 29

Michael J Murray, University of Kansas

Photon Collisions at the LHC

Because of its very high energies and luminosity the Large Hadron Collider could also be called the Large Photon Collider. In this talk I will discuss photon nucleus, photon proton and photon-photon collisions at the LHC. Such collisions serve as very clean probes for the hadron wave-function and have excellent sensitivity to new phenomena in both QCD and electroweak physics.

October 6

Alexey Petrov, Wayne State University

Glueball Molecules

Glueballs are predicted in various QCD-based approaches as particles whose valence degrees of freedom are gluons. However, experimental searches for the glueballs are complicated because of the quantum-mechanical mixture of the glueball and regular qq-bar states with the same quantum numbers. I will discuss a new mechanism for hadronization of glueball states, in which glueballs form molecular bound states with regular hadrons, and its implications for the observed spectrum of hadrons. I argue that an anomalously long lifetime of the π(1800) state could result from the the fact that significant part of its wavefunction corresponds to the glueball-pion molecular state.

October 10

Rob Pisarski, BNL

The phase diagram of QCD: effective theory, tetraquarks, and (almost) Lifshitz points

I outline the development of an effective theory to describe the phase diagram of Quantum ChromoDynamics (QCD) at nonzero temperature and density. The goal is to develop a theory which can bridge numerical simulations on the lattice with the computation of transport coefficents. This is done by combining a linear sigma model for the chiral phase transition with a matrix model for deconfinement. In this context, I discuss how tetraquarks can affect the phase diagram, and even produce two phase transitions for very light quarks. I conclude with an outline of the role which Lifshitz points might play.

October 20

Sean Liddick, NSCL/MSU

Rare Isotope Science: Atoms to Stars

Understanding the properties of the atomic nucleus is one of the key goals of low-energy nuclear science. The continuous expansion in the availability of short-lived isotopes for experimental studies enables investigation of specific combinations of proton and neutrons that can isolate certain features of the nuclear many-body problem. Knowledge of nuclear properties far from stability can then be used in other areas such as astrophysics where nuclear science input is needed over a wide range of proton and neutron numbers to predict elemental abundances during the explosive final moments of a massive star. The National Superconducting Cyclotron Laboratory on the campus of Michigan State University (MSU) currently provides a large quantity of rare isotopes for sensitive experimental study. At the same time work is progressing on the Facility for Rare Isotope Beams (FRIB), a U.S. user facility currently under construction at MSU for the production of rare isotope beams. This talk will present some of the science performed at the NSCL with a few specific examples and describe the status and prospects when FRIB is completed.

October 27

Bilas Pal University of Cincinnati

Charmless hadronic B decays: recent Belle results and Belle II prospects

Charmless hadronic B decays are a good testing ground for the Standard Model (SM) of Particle Physics. The dominant amplitudes are CKM suppressed tree diagrams and/or bâ†'s or bâ†'d loop ("penguin") diagrams. Non-SM particle could appear in the loop, and hence these decays are sensitive to search for the New Physics. Some of the recent measurements of charmless hadronic B decays from Belle and the Belle II prospects will be discussed.

November 3

Tania Robens, MSU

Constraining extended Higgs sectors at the LHC and beyond

With the discovery of the Higgs boson in 2012, particle physics has entered an exciting era. While the LHC experiments currently do not find clear evidence for physics beyond the Standard Model, theoretical and experimental uncertainties still leave enough space for new physics. I will discuss the status of two scenarios that extend the scalar sector of the Standard Model, vis., a model with a simple scalar extension as well as a two Higgs doublet model with a dark matter candidate.

November 10

Yasuki Tachibana, Wayne State University

Medium Response to Jets in Heavy Ion Collisions

We study the jet structure modification in the quark-gluon plasma (QGP) with the inclusion of the medium response effect. The jet structures in heavy ion collisions are significantly modified by the processes involving strong interactions with the QGP fluid. Meanwhile, the jets are supposed to deposit their energy and momentum through these interactions and cause flows as the hydrodynamic medium response in the QGP fluid. The particles produced from the jet-induced flow are observed as part of the jets, and also modify the jet structures in the final state. We apply coupled jet-fluid model consisting of jet transport equations and relativistic hydrodynamics equations with source terms to perform the simulations of jet events and study how the hydrodynamic medium response can contribute to the jet observables in heavy ion collisions.

November 17

Carlos Argüelles, MIT/WIPAC

New physics searches with >TeV neutrinos

IceCube observation of high-energy astrophysical neutrinos has opened the astrophysical neutrino window. As we accumulate statistics IceCube not only starts characterizing the astrophysical neutrino component, but also makes improved measurements of the highest energy atmospheric neutrinos. In this talk I will discuss how we can use both high-energy atmospheric neutrinos as well as astrophysical neutrinos as a probe of new physics.

November 28

Simon Eidelman, Budker Institute of Nuclear Physics and Novosibirsk State University

Muon Anomalous Magnetic Moment and Low Energy e+e- Annihilation

The Muon Anomalous Magnetic Moment is one of the most precisely measured quantities in modern physics. Its measured value, known to 0.5 10^{-6} precision, is larger than the theoretical prediction in the Standard Model by almost 4 standard deviations. We discuss various aspects of the problem and explain how precise measurements of the low energy process e+e- into hadrons come into play.

December 1

Jason Chang, LBNL

The half-life of a free neutron from Lattice QCD

The axial coupling of the nucleon, $g_A$, is a fundamental property of neutrons and protons. The long-range nuclear force between nucleons and the $beta$-decay rate of a free neutron both depend on $g_A^2$. This coupling therefore underpins all of low-energy nuclear physics, controlling, for example, the primordial composition of the universe. While the value of $g_A$ is, in principle, determined by the fundamental theory of nuclear strong interactions, Quantum Chromodynamics (QCD), it is daunting to compute, as QCD is non-perturbative and has evaded an analytic solution. Lattice QCD provides a rigorous, non-perturbative definition of the theory through a discretised formulation which can be numerically implemented. Using an innovative computational method, we resolve the two outstanding challenges identified by the lattice QCD community for determining $g_A$: we demonstrably control excited state lattice artifacts and are able to utilise exponentially more precise numerical data resulting in the determination $g_A^{QCD} = 1.275 pm 0.012$, compatible with the experimentally measured value and with unprecedented precision of $0.95%$. This milestone calculation signals a new era of precision lattice QCD applications to high-impact experimental searches for physics beyond the Standard Model in nuclear environments.

December 8

Ciaran Hughes, FNAL

Searching for beauty-fully bound tetraquarks using lattice Non-relativistic QCD

Systems with even a moderate number of quarks, including light nuclei, are difficult to study theoretically, both when using a first-principles methodology (such as lattice QCD) or from within models. Instead of the these complicated systems, studying another realistic system where the dynamics naturally simplifies would greatly enhance our understanding of how quarks bind and enable us to make more robust predictions from models. Recently one such system has generated significant attention in the literature: a stable (in QCD) four quark bound-state composed of two bottom-quarks and two anti-bottom quarks, which could be experimentally accessible at the LHC. This seminar will explore the exciting search for this tetraquark state using the first-principles lattice QCD methodology.

Winter 2017

January 20

David Cinabro, Wayne State University

Search for Type IA Supernova subclasses

In response to a recently reported observation by Milne and collaborators of evidence for two classes of Type Ia Supernovae (SNe Ia) distinguished by their brightness in the rest-frame near ultraviolet (NUV), I report on a search for the phenomenon in publicly available light-curve data. My collaborators and I use the SNANA supernova analysis package to simulate SN Ia-light curves in the Sloan Digital Sky Survey Supernova Search (SDSS) and the Supernova Legacy Survey (SNLS) with a model of two distinct ultraviolet classes of SNe Ia and a conventional model with a single broad distribution of SN-Ia ultraviolet brightnesses. We compare simulated distributions of rest-frame colors with these two models to those observed in 158 SNe~Ia in the SDSS and SNLS data. The SNLS sample of 99 SNe~Ia is in clearly better agreement with a model with one class of SN~Ia light curves and shows no evidence for the reported distinct NUV sub-classes. The SDSS sample of 59 SNe~Ia with poorer color resolution does not distinguish between the two models.

February 17

Richard (Rick) Field University of Florida

Studying the Energy Dependence of the Underlying Event at the Tevatron and the LHC

I will review the CDF "underlying event" (UE) studies at the Tevatron starting with the first studies in 2000 and the first Tevatron QCD Monte-Carlo model tune, PYTHIA Tune A. I will discuss the extrapolation of the CDF Tevatron PYTHIA tunes to the LHC energies. CDF UE data at 300 GeV, 900 GeV, and 1.96 TeV can be combined with LHC data at 7 and 13 TeV allowing for a detailed study of the energy dependence of the various components of the UE at five center-of-mass energies. The CDF 300 GeV and 900 GeV data are a result of the "Tevatron Energy Scan" which was performed just before the Tevatron was shut down. The overall "transverse" region of can be divided into the "transMAX" and "transMIN" contributions. The "transMIN" is very sensitive to the multiple parton interaction component (MPI) of the UE, while "transDIF" ("transMAX" minus "transMIN") is very sensitive to the initial-state and final-state radiation. The "transMIN" and "transDIF" observables have very different energy dependences. The PYTHIA QCD Monte Carlo model tunes do a fairly good (although not perfect) job in describing the energy dependence of "transMIN" and "transDIF". I have enjoyed very much being involved with the CDF UE measurements at 300 GeV, 900 GeV, and 1.96 TeV, as well as the more recent CMS UE studies 7 and 13 TeV. Combined Tevatron and LHC UE studies will result in improved QCD Monte Carlo models and more accurate simulations of hadron-hadron collisions.

Matt Baumgart Rutgers University

Capture and Decay of Electroweak Wimponium

The spectrum of Weakly-Interacting-Massive-Particle (WIMP) dark matter generically possesses bound states when the WIMP mass becomes sufficiently large relative to the mass of the electroweak gauge bosons. In the specific case of the wino, we find that the rate for bound state formation is suppressed relative to direct annihilation, and so provides only a small correction to the overall annihilation rate. The implications for general nonabelian dark sectors though, show that bound state formation must be considered in any thorough treatment of observability. The soft photons radiated by the capture process and by bound state transitions could permit measurement of the dark matter's quantum numbers.

February 24

Carlos Wagner, Argonne National Laboratory; Enrico Fermi Institute and Kavli Institute for Cosmological Physics, UChicago

Higgs Coupling Measurements and New Physics

Precision measurements of the 125 GeV Higgs resonance recently discovered at the LHC have determined that its properties are similar to the ones of the Standard Model (SM) Higgs boson. However, the current uncertainties in the determination of the Higgs boson couplings leave room for significant deviations from the SM expectations. In fact, if one assumes no correlation between the top-quark and gluon couplings to the Higgs, the current global fit to the Higgs data lead to central values of the Higgs couplings to the bottom-quark and the top-quark that are about 2 σ away from the SM predictions. In this talk, we shall discuss theoretical models which could lead to a sizable enhancement (suppression) of the top-quark (bottom-quark) coupling to the Higgs and present some testable implications of these models. The speaker is the head of the ANL High Energy Physics Theory Group and professor at the EFI and the KICP, University of Chicago.

March 3

Michael Kohl, Jefferson Lab

Anomalies in fundamental observables - old physics or new physics?

Anomalies in measurements of the proton elastic form factors, the proton charge radius, and the muon magnetic moment have given rise to speculations about missing elements of old or new physics, such as two-photon exchange or the postulation of new particles still to be discovered, which could also be linked to dark matter. A framework of new experiments aims to resolve these puzzles by stringently testing the offered hypotheses. I will discuss aspects of the OLYMPUS, MUSE, TREK and DarkLight experiments and show how they are intertwined.

March 10

Yu Gao, Wayne State University

Searches for Extra Neutrinos

Extra species of non-Standard-Model neutrinos have been an appealing direction of new physics from both experimental phenomena and several theoretical frameworks. Their possible masses, if accessible to current experiments, can range from the eV scale up to multiples of TeV. For light sterile neutrinos I will discuss the recent developments in their measurement through high-energy atmospheric and very short baseline neutrino oscillations. I will also discuss the searches for heavy extra neutrinos from direct and indirect detection, as well as the prospects of directly probing the heavy neutrinos at the large hadron collider.

March 13

Matthias Neubert, Mainz University

LHC probes of axion-like particles

We argue that the study of rare Higgs decays in the high-luminosity run at the LHC can probe axions and axion-like particles (ALPs) in a wide range of parameter space, which is otherwise inaccessible to experimental searches. If the ALP decays predominantly into photons, our strategy covers the current "gap" in the mass range between 1 MeV and 60 GeV down to photon-axion coupling as small as 10^(-6)/TeV. An ALP is this parameter range can explain the anomalous magnetic moment of the muon and is consistent with electroweak precision tests and flavour constraints. In our analysis we consider the most general effective Lagrangian for a spin-0 particle protected by a shift symmetry, motivated by many extensions of the Standard Model with a spontaneously broken global symmetry.

March 24

Todd Pedlar, Luther College

Spectroscopy of Heavy Quarkonia and Related States at Belle and Belle II

In this talk, contributions made in the spectroscopy of heavy quarkonium and quarkonium-like states by the Belle Collaboration over the past decade will be discussed. The focus will be on both bottomonium and charmonium-related states including the most recent studies of the charged Zb and Zc states reported in the past few years by Belle. Prospects for further study of these systems in the future Belle II Experiment will also be presented. Matt Barrett 31 March David Gerdes University of Michigan The Coolest Place in the Solar System: New Worlds Beyond Neptune and the Hunt for Planet Nine The region beyond Neptune contains thousands of small, icy worlds that take centuries or even millennia to orbit the Sun. These "cosmic leftovers" constitute an archaeological record of the processes that shaped our Solar System. The objects with the longest orbital periods--some of which have been discovered by my group--display a statistically improbable orbital alignment that may result from the presence of a distant ~10 Earth-mass "Planet Nine". I'll describe how we are using data from the Dark Energy Survey, which was designed for extragalactic astronomy--to make exciting new discoveries in our own backyard, and discuss our ongoing search for Planet Nine.

April 7

Kirsten Tollefson Michigan State University

A New Way to Look at the Sky with the HAWC Gamma-Ray Observatory

The High Altitude Water Cherenkov (HAWC) Gamma-ray Observatory was completed in March 2015 and is now giving us a new view of the sky. HAWC is a continuously operating, wide field-of-view observatory sensitive to 100 GeV 100 TeV gamma rays and cosmic rays. It is 15 times more sensitive than previous generation extensive air shower gamma-ray instruments. It serves as a "finder" telescope and monitors the same sky as gamma-ray satellites (Fermi), gravity-wave (LIGO) detectors and neutrino observatories (IceCube) allowing for multi-wavelength and multi-messenger observations. HAWC hopes to answer questions such as "what is dark matter?" and "where do cosmic rays come from?" by observing some of the most violent processes in our Universe. I will present highlights from HAWC's first year of operation.

April 14

Amaresh Datta University of HawaiÊ"i at MÄnoa

Search for Antideuterons in Cosmic Ray Data from AMS-02 and Understanding the Deuteron/Antideuteron Production Mechanism from NA61 Data

Detection of antideuterons produced from dark matter annihilations or decays are complementary to direct detection techniques that probe the scattering cross-sections of dark matter. Low energy antideuterons are a most interesting probe because of their ultra-low astrophysical background, the dominant source of which are the interactions between cosmic-ray protons and interstellar medium (mostly H, He). High production threshold and a steep cosmic-ray spectrum, however, ensure a low background from such processes. We search for antideuterons in cosmic-ray data recorded by Alpha Magnetic Spectrometer (AMS-02) on board the International Space Station (ISS). Production of antideuterons and deuterons in nuclear interactions is a complex non-perturbative process. Using NA61/SHINE data (at CERN SPS) from p+p interactions with 158 GeV/c beam on liquid H target, we are working towards measurements of cross-sections of deuteron production. Comparison between cross-section measurements with predictions using models of coalescence between protons and neutrons will provide insight into the production mechanism and will help improve models. Extending the analysis techniques, measurements of antideuteron cross-sections will be helpful in limiting astrophysical background in AMS-02 data.

April 21

David McKeen, University of Pittsburgh

Neutrino Portal Dark Matter

Dark matter that interacts with the standard model (SM) through the "neutrino portal" is a possibility that is relatively less well studied than other scenarios. In such a setup, the dark matter communicates with the SM primarily through its interactions with (both mostly sterile and mostly active) neutrinos. In this talk, I will motivate neutrino portal dark matter and discuss some new tests of this possibility.

Fall 2016

Sept 16

Thomas Weiler, Vanderbilt University

Trends in Astrophysical Neutrino Data

After many years of waiting we now have a few years worth of astrophysical neutrino data. The "trickle-in" rate of signal events at the largest astro-neutrino detector, iceCube, is about 14events/year. We will discuss the trends exhibited by the ~50 accumulated events. Trends to be discussed include a possible North-South hemispherical asymmetry, an energy break in a single power-law spectrum, extragalactic versus galactic origins, and the possibility for neutrino flavor to shed light on cosmic acceleration mechanisms. (Truth in advertising: I am not a member of any experimental collaboration.)

October 21

Roy Briere Carnegie Mellon University

An Overview of BESIII Physics

BESIII began taking physics data on e+e- collisions in the 2-5 GeV energy range in 2009. I will give an overview of the datasets acquired and review some interesting physics results. Topics include weak flavor physics with D mesons (including quantum correlations), charmonium results, studies of exotic charmonium states (XYZ), and low-energy hadron physics.

November 4

Jacquelyn Noronha-Hostler, University of Houston

Going beyond the RAA to v2 puzzle

Event-by-event fluctuations caused by quantum mechanical fluctuations in the wave function of colliding nuclei in ultrarelativistic heavy ion collisions were recently shown to be necessary for the simultaneous description of RAA as well as the elliptic and triangular flow harmonics at high pT in PbPb collisions at the Large Hadron Collider. In fact, the presence of a finite triangular flow as well as cumulants of the flow harmonic distribution that differ from the mean are only possible when these event-by-event fluctuations are considered. In this talk, I combine event-by-event viscous hydrodynamics and an energy loss mode to make predictions for high pT RAA, v2{2}, v3{2}, and v2{4} in PbPb collisions at √sNN = 5.02 TeV. Additionally, new experimental observables are presented that can help distinguish between different energy loss mechanisms. Sean Gavin Wednesday November 9 4 pm Abhishek Sen BNL Technical challenges understanding heavy ion collisions in experiment and theory The bulk of hot and dense matter created by heavy ion collisions at RHIC behaves like an almost ideal fluid. In order to understand the hot QCD in detail, we need an analysis of heavy ion collision experimental data and theory, together with the dynamical modeling which connects them. The bridge between theoretical modeling and experimental observations is crucial to draw valid conclusions about the properties of QCD matter. An overview of technical challenges in experiment and theory will be presented.

November 11

Abderahmen Zoghbi, University of Michigan

Decoding the heartbeats of the Galactic black hole GRS 1915+105

GRS 1915+105 is a Galactic stellar-mass black hole that shows the most extreme variability properties among all known black holes. It shows coherent and stable periodic patterns in its X-ray emission not matched by any other object, which are suggestive of accretion instabilities. The fact that it also shows jets and outflow winds, makes it an excellent laboratory for understanding the stability of the accretion process and the inflow/outflow interaction. I will present results from recent state of the art X-ray observations of this object. We are able, for the first time, to probe changes in the accretion disk during the coherent oscillations, observe changes in the disk content as instabilities progress, and locate where the winds are launched from.

December 2

Ron Soltz Lawrence Livermore, National Laboratory

From Quark Soup to Jets: A peripatetic view of the quark gluon plasma

We review progress in understanding the properties and composition of the Quark Gluon Plasma, from the formulation of QCD through the present, including both successes and failures in developing this understanding. Specific attention is given to measuring and modeling the space-time evolution of the soft physics component before proceeding to describe the current research program which seeks to do the same for the hard/jet physics sector through the JETSCAPE framework under development at WSU.

Masha Baryakhtar, Perimeter Institute

Searching for Ultralight Particles with Black Holes and Gravitational Waves

The LIGO detection of gravitational waves has opened a new window on the universe. I will discuss how the process of superradiance, combined with gravitational wave measurements, makes black holes into nature's laboratories to search for new light bosons. When a bosonic particle's Compton wavelength is comparable to the horizon size of a black hole, superradiance of these bosons into bound "Bohr orbitals" extracts energy and angular momentum from the black hole. The occupation number of the levels grows exponentially and the black hole spins down. For efficient superradiance of stellar black holes, the particle must be ultralight, with mass below 10^-10 eV; one candidate for such an ultralight boson is the QCD axion with decay constant above the GUT scale. Measurements of BH spins can disfavor or provide evidence for an ultralight axion. Particles transitioning between levels of the gravitational "atom" and annihilating to gravitons may produce thousands of monochromatic gravitational wave signals, turning LIGO into a particle detector.

Winter 2016

January 29

Ahmad Idilbi, WSU

Hadronic Matrix Elements in (1+2) Dimensions

Hadronic matrix elements with longitudinal and transverse dependence play an important role in a wide variety of QCD related phenomena. Among other things, such quantities are required to address certain issues in hadronic spin physics, to make predictions for the transverse momentum dependent spectrum of the Higgs boson production at the LHC, to obtain three-dimensional hadronic tomography and for jet broadening (and other observables) of jets traversing a hot and dense medium. In my talk I will review the main subtle issues regarding transverse momentum dependent (TMD) functions, how they are resolved and certain properties obtained for the newly defined TMD functions. Especially I will consider generalized TMDs, TMD parton distribution functions and the jet quenching parameter q-hat. Time allows, I will discuss some of the intriguing remaining open questions that span most of the topics mentioned above.

February 12

Claude Pruneau, WSU

Bayesian Statistics

February 26

Matt Barrett, WSU

Particle Identification at Belle II

The Belle II experiment is an upgrade of the Belle experiment that will run at an instantaneous luminosity forty times higher than its predecessor, and is projected to record 50 ab-1 of data. Running at this luminosity requires many changes, including the installation of new sub-detectors. The status of the construction and testing of Belle II will be described, with a focus on the new time-of-propagation (TOP) sub-detector used for particle identification, together with the motivation, prospects, and schedule for the experiment.

March 4

Richard Lebed, Arizona State University

Excursions to Exotic Destinations

Following on from the generalities in my colloquium about the discovery and nature of the newly discovered exotic hadrons, this seminar summarizes my own research in this very active area. I discuss whether tetraquarks in large Nc QCD arise naturally or not; then I look at the dynamical diquark picture in a bit more detail to summarize its successes and shortcomings; what the "cusp effect" is, and how it can synchronize resonance masses with opening hadron thresholds; how to use the "quark-counting rules" of high-energy QCD to discern exotic structure; whether hidden-strangeness exotics have been seen and where to look for them; and lastly, brand-new work on whether hidden-charm, hidden-strangeness tetraquarks have already been seen.

March 7

Andreas Kronfeld, Fermilab

Lattice QCD and Flavor-Changing Neutral Currents

Recent lattice-QCD calculations have improved the precision of several hadronic matrix elements. Standard Model predictions for several observables (calculated with these results) are in tension with the corresponding experimental measurements. In the talk, I will give an overview on how lattice QCD calculations are done, using neutral B-meson mixing as a working example. I will then discuss the phenomenology of B mixing and also semileptonic decays mediated by flavor-changing neutral currents.

March 25

Michael Kordell, WSU

Jets in p(d)-A Collisions: Centrality Dependent Effects: Color Transparency or Energy Conservation?

The production of jets, and high momentum hadrons from jets, produced in deuteron (d)-Au collisions at the relativistic heavy-ion collider (RHIC) and proton (p)-Pb collisions at the large hadron collider (LHC) are studied as a function of centrality, a measure of the impact parameter of the collision. A modified version of the event generator PYTHIA, widely used to simulate p-p collisions, is used in conjunction with a nuclear Monte-Carlo event generator which simulates the locations of the nucleons within a large nucleus. We demonstrate how events with a hard jet may be simulated, in such a way that the parton distribution function of the projectile is frozen during its interaction with the extended nucleus. Using our approach, we demonstrate that the puzzling enhancement seen in peripheral events at RHIC and the LHC, as well as the suppression seen in central events at the LHC are mainly due to mis-binning of central and semi-central events, containing a jet, as peripheral events. This occurs due to the suppression of soft particle production away from the jet, caused by the depletion of energy available in a nucleon of the deuteron (in d-Au at RHIC) or in the proton (in p-Pb at LHC), after the production of a hard jet. We conclude that partonic correlations built out of simple energy conservation are mostly responsible for such an effect.

April 5

Peter Schwerdfeger, The New Zealand Institute for Advanced Study, Massey University, Auckland

Beyond the Standard Model - the Variation of Fundamental Constants in Space-Time

Fundamental constants like the speed of light c, the Planck constant h or the gravitational constant G play defining roles in physics and chemistry. Modern theories attempting to unify all four fundamental forces of nature suggest that all fundamental constants may vary in space and time. A small deviation from these constants would result in a completely different universe not able to sustain life. The search for small variations currently constitutes one of the most exciting areas of modern physics as it goes beyond the standard model in particle physics. In fact, this area of research is motivated by new theories unifying gravity with the other three fundamental interactions, as well as by a number of cosmological models. From atomic clock experiments we already know that the variation of the fine structure constant Î"α/α is less than ~10-17 per year, and the variation in the electron to proton mass ratio Î"μ/μ (μ=me/mp) is similarly small with less than ~10-15 per year. Quasar and Big Bang nucleosynthesis data gave hints for non-zero variations, which, however, have not been confirmed yet. For further progress in this area it is important to find enhanced effects in atoms or molecules for the variation of fundamental constants. Our research group, in close collaboration with V. V. Flambaum (Sydney) and many others, currently searches for best candidates to measure variations of fundamental constants in future high-precision laboratory experiments.

April 15

Joshua Spitz, U of M

Kaon decay-at-rest and a very unique neutrino

When a charged-kaon decays at rest, it usually (64%) produces a monoenergetic muon neutrino at 236 MeV. Recently, this unique neutrino has been identified as an important tool for studying neutrino oscillations at short baseline, probing the nucleus, and understanding the neutrino interaction itself. I will discuss the "kaon decay-at-rest" concept for neutrino physics and present a set of experiments that will be able to perform the relevant measurements in the next few years.

May 26

Martin Jung, Tech. Univ. Munich

Bounds on new physics from electric dipole moments

Electric dipole moments are extremely sensitive probes for additional sources of CP violation in new physics models. The multi-scale problem of relating the high precision measurements with neutrons, atoms and molecules to fundamental parameters can be approached model-independently to a large extent; however, care must be taken to include the uncertainties from especially nuclear and QCD calculations properly. The resulting bounds on fundamental parameters are illustrated in the context of Two-Higgs-Doublet models.

Fall 2015

September 18

Clint Young, MSU

Electromagnetic recombination spectra at the quark-hadron phase transition

Photons are radiated when quarks and gluons hadronize. This is true not only in jets but also in heavy ion collisions, where a thermalized plasma of quarks and gluons cools into a weakly interacting gas of hadrons. In the quark-meson model at finite temperature, quarks coalesce into pions and radiate like any other accelerating electric charge. The ratio in the yields of these photons to the yields of pions in our simplified model goes roughly as $e^2/g^2_{qbar{q}pi}$. Because $g_{qbar{q}pi}$ is a parameter of an effective theory and is fit to data, this ratio is merely an estimate, but for the standard range of values used, this ratio is 5-10%. The photon production at hadronization of the quark-gluon plasma will be part of the solution to the photon puzzle, both because it enhances the yield of photons at momenta of about 2 GeV/c, and because the photons produced are made at late times and will have significant elliptic flow.

October 16

Kendall Mahn, MSU

New antineutrino oscillation results from the T2K experiment

One of the most promising investigations of beyond-the-Standard-Model physics has been the study of neutrino oscillation, that is, the conversion of neutrinos from one flavor to another as they propagate. While neutrino oscillation is studied in a wide variety of experiments, accelerator based experiments, such as T2K, use a muon neutrino or antineutrino beam as a probe. This talk will describe the first results from T2K for antineutrino disappearance, a test of non-standard matter interactions, and the initial search for electron antineutrino appearance. In particular, the presence of electron antineutrino appearance transition is a necessary requirement for future CPV experiments with neutrinos, and has not been observed yet.

October 23

Ruth Van der Water, FNAL

New-Physics Searches in B-meson semileptonic decays with Lattice QCD

B-meson decays provide a wealth of complementary observables that enable tests of the Standard Model and probe different new-physics scenarios, provided sufficiently precise and reliable experimental measurements and theoretical calculations. Recently several tantalizing 2-3sigma tensions have been observed in B-meson decays; new experimental measurements, including observations of heretofore unseen processes have also appeared. The Fermilab Lattice and MILC Collaborations recently completed lattice-QCD calculations of the underlying hadronic form factors for B->pi and B->K semileptonic decays. Here I summarize the numerical form-factor computations and then discuss the phenomenological implications. Using the FNAL/MILC form factors, I present results for observables in the Standard Model for Bâ†'Ï€(K)l+l-, Bâ†'Ï€(K)νν̅, and Bâ†'Ï€Ï"ν decays. For Bâ†'Ï€(K)l+l-, I then compare the Standard-Model expectations with experimental measurements. Assuming the Standard Model, I determine the Cabibbo-Kobayashi-Maskawa matrix elements |V_{td}|, |V_{ts}|, and their ratio from B-meson semileptonic decays. Alternatively, taking the CKM matrix elements from unitarity, I constrain new-physics contributions at the electroweak scale.

October 30

Mark Reynolds, UM

Probing the Spin Evolution of SMBHs at Cosmological Distances

The co-evolution of a super-massive black hole (SMBH) with its host galaxy through cosmic time is encoded in its spin. At z>2, super-massive black holes are thought to grow mostly by merger-driven disk accretion leading to high spin. It is not known, however, whether below z<1 these black holes continue to grow in this way (so called coherent accretion) or instead in a less organized more erratic manner (chaotic accretion). An established method of measuring the spin of black holes is through the study of relativistic reflection features from the inner accretion disk. I will present recent work wherein we have for the first time directly measured the spin of cosmologically distant SMBHs, by taking advantage of the boost in S/N provided by the strong gravitational lensing of distant Quasars.

November 13

Sarah Gallagher, University of Western Ontario

Winds, Winds Every Where: Radiatively Driven Outflows from Supermassive Black Holes

Supermassive black holes reside in the centers of every massive galaxy. In relatively brief spurts, black holes grow as luminous quasars through the infall of material through an accretion disk. Remarkably, the light from the accretion disk can outshine all of the stars in the host galaxy by a factor of a thousand, and this radiation can also drive energetic mass outflows. Mass ejection in the form of winds or jets appears to be as fundamental to quasar activity as accretion, and can be directly observed in many objects with broadened and blue-shifted UV emission and absorption features. A convincing argument for radiation pressure driving this ionized outflow can be made within the dust sublimation radius. Beyond, radiation pressure is still important, but high energy photons from the central engine can now push on dust grains. This physics underlies the dusty wind picture for the putative obscuring torus. I'll describe our model of the dusty wind and evaluate its successes and shortcomings in accounting for observed properties of quasars such their mid-infrared power, fractions of hidden objects, and column densities of important ions.

November 20

William Wester III, FNAL

Non-WIMPy Dark Matter Searches at Fermilab

"What is the nature of dark matter" that accounts for approximately 80% of the matter in the universe? Gaining popularity is to invoke the possibility that "Non-WIMPy" new particles form the dark matter in contrast to usual Weakly Interacting Massive Particles hypothesis. Novel ideas and novel experiments, often at a very small scale, are exploring large areas of previously unexplored parameter space. Plus, they are a lot of fun too!

December 4

Mike Lisa, tOSU

Global Hyperon Polarization in Ultra-relativistic Heavy Ion Collisions Measured by the STAR Experiment at RHIC

Non-central collisions between ultra-relativistic heavy ions involve millions of h-bar of angular momentum. It is unclear how much if any of this angular momentum is transferred to the quark-gluon plasma created at midrapidity. Such a transfer may arise via a spin-orbit coupling in QCD or, in a hydrodynamic picture, through shear forces that generate a vorticity in the fluid. While thermalization of energy and light-flavor chemical degrees of freedom in heavy ion collisions is well-established, thermal distribution of angular momentum among all available substates is far from clear. Angular momentum thermalization or vorticity in the QGP may result in a correlation between the spin of emitted hadrons and the direction of the angular momentum of the overall system. This "global polarization" is distinct from polarization relative to the particle production plane observed at very forward angles in p+p collisions. Due to their so-called self-analyzing nature, hyperons reveal their spin orientation in their decay. STAR has measured the first non-zero signal of the polarization of Lambdas and AntiLambdas relative to the direction of the collision's angular momentum, estimated by the event reaction plane, at several collision energies. I will discuss details of the analysis, the energy and centrality dependence of the signal, and two methods of quantifying the polarization. I will also discuss detector and accelerator upgrades that will allow us to study this new signal in far greater detail in the upcoming second phase of the Beam Energy Scan at RHIC.

Winter 2015

February 6

Professor Anne Sickles University of Illinois at Urbana-Champaign

The Lighter Side of Heavy Ion Collisions: What have we learned from colliding large nuclei with protons, deuterons and He3?

The stated goal of heavy ion physics is to produce and study the high temperature state of quantum chromodynamics where quarks and gluons are not confined inside hadrons, the quark gluon plasma. Large nuclei are used to maximize the size of the created matter. Asymmetric collisions, where a proton or deuteron collides with a large nucleus have been used to study modifications to the bound nucleons in nuclei in the absence of the quark gluon plasma Recent measurements from both RHIC and the LHC show effects very similar to those seen in heavy ion collisions which are attributed to the quark gluon plasma. I'll discuss the experimental situation, including very recent results on He3+Au collisions from PHENIX.

February 20

Dr. John R., Arrington Argonne National Laboratory

Nucleon form factors: detours, U-turns, roundabouts, and a head-on collision

Jefferson Lab experiments utilizing polarization degrees of freedom to extract proton and neutron form factors have dramatically changed our understanding of the structure of nucleons. These experiments have illuminated the role of quark orbital angular momentum, allowed for the separation of up- and down-quark distributions, and demonstrated the importance of diquark correlations in proton structure. However, it has been a somewhat bumpy ride: the first polarization measurements of the proton form factors at high Q^2 showed a discrepancy with earlier unpolarized extractions, leading to a detailed theoretical and experimental reexamination of two-photon exchange contributions. More recently, ultra-precise measurements of the proton radius from muonic hydrogen are at odds with extractions from electron scattering. I will summarize the Jefferson Lab form factor program, covering what we have learned about the structure of the proton, recent results on two-photon exchange corrections and future plans aimed at resolving the proton radius puzzle.

March 6

Scott Pratt, Michigan State University

Have we finally "Seen" the Quark Gluon Plasma?

For the past 20 years experiments have attempted to create and observe the quark gluon plasma in heavy ion collisions, but it has proven difficult to quantitatively characterize its properties from experimental observation. However, during the last few years a new class of experimental observations based on correlations driven by local charge conservation is proving to be able to address one of our most fundamental questions about the chemical makeup of matter created in heavy ion collisions: "Does it have the properties, e.g. the density of quarks, one would expect from an equilibrated quark gluon plasma. I will show how charge balance functions measured by STAR at the Relativistic Heavy Ion Collider can be interpreted by simple models and infer charge susceptibilities. These will then be compared to values extracted from lattice gauge theory.

April 10

Dr. Mauricio Martinez Guerrero, The Ohio State University

Testing hydrodynamics with a new exact solution of the Boltzmann equation

We present an exact solution to the Boltzmann equation which describes a system undergoing boost-invariant longitudinal and azimuthally symmetric radial expansion for arbitrary shear viscosity to entropy density ratio. This new solution is constructed by considering the conformal map between Minkowski space and the direct product of three dimensional de Sitter space with a line. The resulting solution respects SO(3)_q x SO(1,1) x Z_2 symmetry. We compare the exact kinetic solution with exact solutions of the corresponding macroscopic equations that were obtained from the kinetic theory in ideal and second-order viscous hydrodynamic approximations. The macroscopic solutions are obtained in de Sitter space and are subject to the same symmetries used to obtain the exact kinetic solution.

Fall 2014

September 17

Daniel Cebra Univ. of California

Davis beam energy scan at RHIC

September 24

Itay Yavin, McMaster Univ. & Perimeter Institute

Particle Theory

September 26

Jay Strader Michigan State Univ.

Black Holes in Globular Clusters

October 3

Misty Bentz, Georgia State University

Black Hole Masses in Active Galaxies

October 8

Daniel McKinsey, Yale Univ.

Low-Energy Ionization and Scintillation Response of Liquefied Noble Gases

October 31

Chia-Ying Chiang Wayne State Univ.

Modeling the X-ray Spectra of AGN with a Relativistic Reflection Model

November 5

Minakshi Nayak, Wayne State Univ.

Evidence of the suppressed decay B- to D K-, D to K+ pi- pi0

November 14

Andre de Gouvea Northwestern Univ.

Fundamental Physics with Muons

December 5

Sudeshna Ganguly, Wayne State University

Measurement of branching fractions of rare semi-leptonic D_s decays at Belle