Hadron Ion Tea (HIT) Seminar Series


[formerly the Heavy Ion Tea Seminars]


Nuclear Science Division


Lawrence Berkeley National Laboratory

HIT seminars are on Tuesdays at 3:30pm Pacific Time (unless otherwise noted)

Current Organizers: Jennifer Rittenhouse West, Shujie Li, Farid Salazar and Nu Xu

HIT zoom link

Previous seminars can be viewed on our HIT Youtube Channel

Upcoming seminars

We welcome you back to our Hadron-Ion Tea Seminar Series! All talks are 100% virtual except for local speakers (in-person & zoom) - we hope you join us!

October 4th, 2022, 3:30 PM PDT (Zoom only)

Dr. Yoshitaka Hatta (BNL)

Host: Farid Salazar

Spin Physics Opportunities at the EIC
Slides


I give an overview of high energy QCD spin physics with particular emphasis on physics opportunities at the future Electron-Ion Collider. Topics will include longitudinal spin decomposition, orbital angular momentum, spin at small-x, Ji sum rule and the generalized parton distributions, and transverse single spin asymmetries. I review the recent developments in the field and identify what are the outstanding challenges at the EIC.

October 11th, 2022, 3:30 PM PDT (Zoom only)

Dr. Niklas Mueller (U. Washington)

Host: Farid Salazar

What can QIS do for high energy and nuclear physics?


The possibility to simulate quantum many-body systems with digital quantum computers and analog devices is an exciting opportunity for high energy and nuclear physics. I will present an overview over new directions in two old examples: understanding systems far-from-equilibrium, such as QCD in ultra-relativistic heavy ion collisions, and their approach to thermal equilibrium, and addressing thermal systems in regimes where Monte-Carlo importance sampling techniques face a sign problem. For those of you impatiently waiting for quantum computers to outrun classical computers, I will emphasize that QIS not only allows to make progress computationally, but more importantly conceptually, including previously unexplored aspects such as, e.g. entanglement. I will present a few relevant examples, still far from the ultimate goal QCD, but interesting because of their interdisciplinary relevance for high energy and nuclear physics, condensed matter theory and quantum information science.


Tuesday, October 18th, 2022, 3:30 PM PDT (in person & zoom)

Dr. Minjung Kim (UC Berkeley and LBNL)

Host: Nu Xu

Quarkonium Production in Heavy-ion Collisions at the LHC

Measurements of J/ψ production have been a valuable probe to study the properties of the hot and dense medium created in heavy-ion collisions, also known as the quark-gluon plasma (QGP). Experimentally, the first glimpse of the QGP was provided by collisions of lead beams at the Super Proton Synchrotron (SPS) in the late 90s via the measurements of J/ψ production. The suppression of J/ψ production in Pb–Pb collisions with respect to p–A collisions was observed, which was proposed as a smoking gun of the QGP as a consequence of colour screening in the QGP medium keeping charmed quark-antiquark pairs from binding to each other.

The higher collision energy at the Large Hadron Collider (LHC) with respect to previous collision programs at SPS and RHIC opened new perspectives on quarkonium measurements due to the increased heavy quark production cross section. The large data samples collected at the LHC based on the excellent performance of the LHC and the four experiments provided precise measurements of charmonium and bottomonium production in a wide kinematic range. Moreover, a multitude of new observables including multi-differential measurements of various quarkonium states becomes accessible, which provided crucial inputs to disentangle various quarkonium in-medium effects in the presence of the QGP.

In this talk, a selection of recent quarkonium measurements at the LHC will be discussed.

25 October 2022 Dr. Tyler Hague (LBNL, in person & zoom). Host: Shujie Li

Thursday, October 27th, 2022 3:30 PM PDT (in person & zoom)

Mr. Henry Klest ( Stonybrook University)

Host: Nu Xu

Teaching an Old Experiment New Tricks: Measuring Modern Jet Observables Using Archived H1 e+p DIS Data

A renaissance in jet physics is now underway, with novel, theoretically rigorous approaches to jet measurements being used to probe QCD in new ways using data from hadronic collisions at RHIC and the LHC. It is timely to explore these new techniques using data from high-energy collider experiments, which were recorded before these techniques were developed. In particular, colliders with leptons in the initial state provide a clean and complementary environment to study jets. The H1 experiment was a hermetic, general-purpose detector at the HERA electron-proton collider complex at DESY, which terminated data-taking in 2007. However, the H1 Collaboration continues to be active scientifically, preserving the data and updating analysis software. The H1 dataset therefore remains as accessible for high-quality analyses as that for currently running experiments, making it the ideal playground for testing modern QCD analysis approaches on DIS data before the EIC turns on. This talk will focus on the measurement of groomed event shapes in ep DIS collisions, using a set of novel inclusive observables which leverage recent advances such as the Centauro jet algorithm and precision jet grooming phenomenology. The advantages and challenges of the event-wide grooming technique will be discussed, as well as some lessons learned that are applicable to the EIC physics program.

1 November 2022 Dr. Feng Yuan (LBNL, in person & zoom). Host: Farid Salazar

8 November 2022 Dr. Björn Schenke (BNL). Host: Farid Salazar

Thursday, November 10th, 2022 3:30 PM PDT (in person & zoom)

Dr. Misha Stephanov (UIC)

Host: Nu Xu

15 November 2022 Dr. Tommaso Giani (NIKHEF Amsterdam) Host: Shujie Li Nota bene: Special time 10 am PST

22 November 2022 Dr. Agnieszka Sorensen (U. Washington). Host: Jennifer Rittenhouse West

Thursday, November 29th, 2022 3:30 PM PDT (zoom)

Dr. Jochen Klein (CERN, zoom)

Host: Nu Xu

Physics Program and Detector Development with ALICE3

ALICE 3 constitutes the next-generation upgrade for heavy-ion physics in LHC Runs 5 and 6. It addresses the questions about the quark-gluon plasma which remain inaccessible to other existing or planned experiments, e.g. on the transport properties and thermalisation in the QGP, the formation of hadrons, and the early stages of the plasma evolution. To this end, precise measurements of heavy-flavour probes as well as of electromagnetic radiation are key. The required pointing and tracking performance are achieved with a high-resolution vertex tracker, installed within the beam pipe, and a large-acceptance tracker, both based on monolithic silicon-pixel sensors. The particle identification relies on a combination of a silicon-based time-of-flight detector and a Ring-Imaging Cherenkov detector. In addition, an electromagnetic calorimeter, a muon identifier, and a dedicated forward detector for ultra-soft photons are foreseen. In this presentation, we will explain the detector concept and its physics reach as well as discuss the innovative R&D activities in areas of interest for HEP experiments in general.

6 December 2022 Dr. Alba Soto-Ontoso (CERN). Host: Farid Salazar

13 December 2022 Dr. Allison Zec (UNH). Host: Jennifer Rittenhouse West

20 December 2022 Dr. Chiara Bissolotti (Argonne). Host: Jennifer Rittenhouse West

Welcome to the 2023 Hadron-Ion Tea Seminar Series! Happy New Year everyone!

17 January 2023, 3:30 PM PDT

Dr. Adam Freese (U. Washington)

Host: Jennifer Rittenhouse West

Spatial distributions of energy and stresses in hadrons


The Lorentz group of special relativity contains a Galilean subgroup, which manifests in the light front picture of spacetime. Light front coordinates thus allow a fully relativistic spatial description of the internal structure and dynamics of hadrons, specifically in the form of two-dimensional densities on the plane transverse to the observer's line of sight. The energy-momentum tensor allows distributions of energy, momentum, spin and stresses to be obtained. In this talk, I elaborate on the physical meaning of light front coordinates, and explain the formalism for determining internal distributions of hadrons. Concrete model examples for the internal structure of mesons are provided.

Thursday, 08.11.2022, 2:30 PM PDT Special date and time! in the Theory Lounge (hybrid)


Dr. Raymond Ehlers (LBNL)

Host: Nicole Apadula/Peter Jacbos

What can we learn about the quark-gluon plasma from reconstructed jets with Bayesian inference?

Slides Youtube



Bayesian inference provides an approach for constraining the parameters of complex models according to the available information. In particular, the wealth of information contained within multi-messenger experimental measurements provides the opportunity for detailed data-model comparison. The need for such rigorous comparison is pervasive throughout science. The JETSCAPE collaboration has now applied this Bayesian approach to the familiar problem of jet quenching. In this talk, I will discuss our recent results, in-progress analysis, and implications for the future of the field.

Wednesday, 06.29.2022, 3:30 PM PDT

Joint Nuclear Theory/HIT seminar! Special date on Wednesday!


Dr. Jennifer Rittenhouse West (LBNL)

Host: Xin-Nian Wang

Diquark Formation as a Breakthrough of Fundamental QCD into Nuclear Physics



A diquark bond formed from valence quarks across a nucleon-nucleon pair has been proposed as the fundamental quantum chromodynamics (QCD) physics causing short-range correlations (SRC) in nuclei. Short-range correlated nucleon-nucleon pairs and the nucleon shell model are the basis for nuclear physics, with SRC accounting for 20% of the nucleons in a nucleus. While SRC have been extensively studied both experimentally and theoretically, notably by the CLAS collaboration in recent years, their underlying cause at the QCD level has remained a mystery. The diquark formation model, if shown to be the cause of SRC in nuclei, represents a breakdown of the assumption of scale separation in effective field theories. Rather than a boundary between scales, however fuzzy and broad, a case is made in this work for diquark formation as a direct breakthrough of the underlying theory, capturing 20% of the physics of nuclear structure.

Tuesday, 06.21.2022, 3:30 PM PDT


Dr. Aihong Tang (BNL)

Host: Xin-Nian Wang

Global Spin Alignment in Relativistic Heavy Ion Collisions : A Progress Review


Slides Youtube


In relativistic heavy ion collisions, quarks can possess global spin polarization in a globally vortical system. Such process is initially induced by the spin-orbital coupling, and the evolution of polarized quarks and the subsequent formation of hadrons involves various interesting physics mechanisms. This phenomena can be studied either by global spin polarization of hyperons or global spin alignment of vector mesons. Recently the STAR collaboration released interesting results of global spin alignment for phi- and K*-mesons. It is found that the surprisingly large value of phi-meson global spin alignment cannot be explained by conventional mechanisms, but can be accommodated by a model invoking the strong force field. In this talk we will review the recent progress in the understanding of global spin alignment, and in particular we will discuss STAR's result and its implications.

Monday, 06.13.2022, 3:00 PM PDT (Hybrid at Persevervance Hall, note special time and date!)


Prof. Ulrich Mosel (Giessen University)

Host: Jennifer Rittenhouse West

Neutrino-nucleus interactions in quantum-kinetic transport theory



The analysis of results from long-baseline experiments such as T2K, NOvA and DUNE requires knowledge of the incoming neutrino energy. The latter has to be reconstructed from only partially measured final states of the reaction. Any theory thus has to go beyond the calculation of inclusive cross sections and has to deliver the full final state of the reaction. Since all present experiments work with nuclear targets not only the initial, first interaction of the incoming neutrino plays a role. In addition, the final state interactions of the initially produced hadrons with the nuclear environment are important and determine the final state. The state-of-the-art method to treat such processes is quantum-kinetic transport theory which has been around since 50 years, but only over the last 20 years major numerical implementations to describe nuclear reactions have become available. In my talk I will illustrate some of the results obtained with such a theory, applied both to nuclear reactions and neutrino-nucleus reactions.


Tuesday, 06.07.2022, 12 PM PDT - Special time!


Dr. Sergey Kulagin (Institute of Nuclear Research, RAS Moscow)

Host: Jennifer Rittenhouse West

What can we say about modification of the bound nucleon at the parton level from global QCD fits?

Slides


We briefly review available experimental observations on nuclear effects in deep-inelastic scattering (DIS). We then briefly discuss a few basic mechanisms responsible for nuclear corrections and review progress in understanding the observed phenomenon focusing on the valence quark region. We report the results of our global QCD analysis which includes a "standard" set of high-energy data for the proton target (DIS, DY production of lepton pair as well as W+- / Z boson production) and also nuclear 2H, 3H, and 3He DIS data. In this analysis we treat nuclear corrections in DIS in terms of a nuclear convolution approach with off-shell bound nucleon. The off-shell correction describes the modification of parton distributions in bound nucleons, which is determined along with the parton distribution functions (PDFs). A number of systematic studies have been performed aiming to estimate the uncertainties arising from the use of various deuterium data sets, from the model of high twist contributions to the structure functions, from the treatment of target mass corrections. We compare our predictions for the ratio F2n/F2p and the d/u ratio of the quark distributions with the results of other analyses as well as with the recent data from the MARATHON experiment.

Tuesday, 05.31.2022, 3:30 PM PDT


Dr. Christopher McGinn (Univ of Colorado Boulder)

Host: Sooraj Radhakrishnannan

Inclusive and Electroweak Boson-tagged Jets as Probes of the Quark-Gluon Plasma and Medium Response

Slides Youtube


Jets, as proxy for hard scattered partons in initial collision of heavy and ultrarelativistic nuclei, are modified significantly relative their vacuum reference counterparts when traversing the subsequently formed hot-and-dense medium of deconfined quarks and gluons known as the Quark-Gluon Plasma (QGP). Specifically, a suppression in the overall production of jets is observed compared to vacuum expectation, as well as a modification to jet fragmentation patterns towards softer fragments. These phenomena are known collectively as 'jet-quenching'. Recently, much attention has been paid to the impact of jet-medium interactions on the medium itself, in searches for medium response and in searches for quenching in small systems (such as proton-nucleus collisions) in the context of observed high-pT v2. Using data taken with the ATLAS detector at the LHC, sqrt(sNN) = 5.02 TeV, jets produced with electroweak boson partners (unmodified by strong-force interactions in QGP) are studied to characterize both the jet production and fragmentation, with the latter providing insight into the necessity of incorporating medium response in theoretical model comparisons. Additionally, simultaneous studies of jet v2 and quenching in big-and-small systems reveals there may be more questions on the exact nature of the jet-medium interactions in both systems and how they lead to the physical final state observed.


Tuesday, 05/24/2022,3:30 PM PDT

Prof. Mike Lisa (Ohio State University)

Host: Xin-Nian Wang

Subatomic Smoke Rings: Polarization and Toroidal Vorticity in the QGP

Slides Youtube


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

Tuesday, 05.17.2022, 3:30 PM PDT


Prof. Jorge Noronha (UIUC)

Host: Xin-Nian Wang

Hydrodynamic Frames: the Good, the Bad, and the Ugly

Slides Youtube


Three of the most cutting-edge experiments in modern science, RHIC, LHC, and LIGO are now producing data whose description requires a major overhaul of our current understanding of what constitutes fluid dynamic behavior in the relativistic regime. In this talk I will explain how the choice of hydrodynamic variables in a system out of equilibrium, i.e., our definition of the so-called hydrodynamic frame, affects the domain of applicability of relativistic viscous fluid dynamics formulations. I will also show how developments in relativistic viscous hydrodynamics obtained in heavy-ion collisions could be instrumental in determining the viscous properties of ultradense matter formed in neutron star mergers.


Tuesday, 05.10.2022, 3:30 PM PDT


Prof. Kenji Fukushima (Univ. of Tokyo)

Host: Feng Yuan

Continuity or Discontinuity between Nuclear and Quark Matter and the Astrophysical Implications


Slides Youtube


In this talk I will review theoretical scenarios of quark matter at high density. Although a phase transition is not logically excluded, a crossover or weak first-order transition is likely to occur. I will explain how the equation of state is constrained by the neutron star observation and demonstrate that the future gravitational wave detection can identify the nature of the quatk matter onset.


Wednesday, 05.04.2022, 3:30 PM PDT (Special date)

(Hybrid talk in the INPA room)

Prof. Carl Schroeder (LBNL/UCB)

Host: Peter Jacobs

Laser-Plasma Accelerators


Slides


Laser-driven plasma-based accelerators (LPAs) are able to sustain extremely large accelerating gradients, orders of magnitude larger than those achievable using conventional metallic accelerating structures. LPA experiments have demonstrated the generation of multi-GeV electron beams in cm-scale plasmas. These high gradients have attracted interest in LPA technology for high-energy collider applications. In this talk, I will review the basic physics of LPAs, LPA research in the BELLA Center at LBNL, and how LPAs can be developed for various applications. Employing LPAs as a linac for an e+e- collider is the most challenging application, and I will discuss the design considerations and expected performance for an LPA-based linear collider. .


Tuesday, 04.26.2022, 3:30 PM PDT

(This will be a hybrid seminar in theTheory Lounge)

Dr. Jan Steinheimer (FIAS)

Host: Sooraj Radhakrishnan

Hyper-nuclei production in heavy-on collisions


slides Youtube


Hypernuclei have been an interesting topic of study for more than half a century. Yet their properties are still not fully understood. In this talk, I will give a short introduction to hypernuclei and how they can be produced. Here, the production of nuclei with one or more units of strangeness from relativistic heavy ion collisions is of particular interest, due to the abundance of strange baryons created. While the absorption of hyperons offers a chance to create large hypercluster in the spectator fragments of nuclear collisions, also the observation of light hypernuclei from the central hot region is of interest. I will discuss how the production probability can be well described by a coalescence mechanism using the UrQMD model over a beam energy range of three orders of magnitude. In addition I will show how the measurement of different nuclei can be used to determine the size of the region of homogeneity from which baryons, that will eventually form (hyper-)nuclei, are emitted . Within this context I will discuss recent interpretations of the centrality dependence of (hyper-)nuclei production.


Tuesday, 04.19.2022, 3:30 PM PDT

Dr. Brandon Kriesten (Center for Nuclear Femtography)

Slides Youtube

Host: Jennifer Rittenhouse West

Quark and Gluon Spatial Distributions in the Nucleon


Studying the role of gluonic observables in exclusive scattering processes is essential as new physics programs, such as an electron ion collider, are planned in unprecedented kinematic regimes. I will present a parameterization of quark and gluon generalized parton distributions (GPDs) calculated using a reggeized spectator model. This parameterization is constrained using a combination of lattice QCD form factor calculations and extracted deep inelastic parton distributions. We evolve our parameterization at leading order in Q2 to the scale of experimental data using a perturbative QCD evolution framework. We demonstrate expected spatial distributions under Fourier transformation using our parametrization. Understanding the behavior of gluon GPDs is a first step towards extracting the gluon contribution to deeply virtual Compton scattering (DVCS) and timelike Compton scattering (TCS) observables at the EIC.

Tuesday, 04.12.2022, 3:30 PM PDT

Dr. Gunther M Roland (MIT)

Host: Sooraj Radhakrishnan

Hot QCD with sPHENIX at RHIC


Slides Youtube


Over the last decades heavy-ion experiments at RHIC and LHC have demonstrated a range of novel QCD phenomena that emerge under conditions of extreme pressure and temperature. New efforts, sPHENIX at RHIC and the upgraded LHC experiments, will begin collecting high precision new data in the next year. These data will allow us to investigate the microscopic origins of observed phenomena in the produced Quark-Gluon Plasma (QGP). Of particular importance will be the complementarity of experiments in the two energy regimes, elucidating the temperature dependence of QGP properties. In this talk I will present the sPHENIX design, construction status and expected performance, and discuss case studies that illustrate key aspects of the sPHENIX physics program.



Tuesday, 03.29.2022, 3:30 PM PST

Prof. MaElena Tejeda Yeomans (Universidad de Colima)

Host: Jennifer Rittenhouse West

Rise and Fall of Lambda and anti-Lambda Polarization from the Core-Corona Model


Slides Youtube


The polarization of particles produced in heavy-ion collisions provides the perfect arena to study amazing phenomena such as the collective rotation of the nuclear medium, the transference of global angular momenta to spin properties of certain particles, and the evolution of these properties when there are drastic changes in the properties of the hot and dense medium. Recently, measurements by STAR collaboration at RHIC and HADES collaboration at GSI show the rising of Lambda and anti-Lambda global polarization with decreasing collision energy. Many models predict the vanishing of global polarization due to the lack of system angular momentum, but the height and location of the expected peaks for both Lambda and anti-Lambda are still not well understood. In this talk I will report on recent work to study Lambda and anti-Lambda global polarization in heavy-ion collisions using the core-corona model, where the source of these hyperons is a high-density core and a less dense corona. I will show that the overall properties of the polarization excitation functions can be linked to the relative abundance of Lambdas and anti-Lambdas coming from the core versus those coming from the corona. We will see how the global polarization peak at the expected ranges of collision energies but, the exact positions and heights of these peaks depend on the centrality class, which is directly related to the QGP volume and lifetime, as well as on the relative abundances of Lambdas and anti-Lambdas in the core and corona regions. Finally, I will talk about the improvements we are making to this model to study polarization properties of other species, and as a probe of critical phenomena in the nuclear medium.

Tuesday, 03.22.2022, 3:30 PM PST

Dr. Xiaojun Yao (MIT)

Host: Xin-Nian Wang

Pure quark and gluon jet observables

Slide Youtube


Disentangling quark- and gluon-initiated jets can help us to better understand fundamental interactions in QCD and use jets as probes of the quark-gluon plasma in heavy ion collisions. Many previous studies relied on the Sudakov factors of some jet substructure observables such as the soft drop jet mass in the tail region and failed to reach a 100% efficiency in the disentangling. In this talk, I will introduce novel jet observables that are made pure quark or gluon in a wide kinematic region. The construction is based on the collinear drop grooming technique and nonperturbative effects are taken into account. I will show both analytic and Monte Carlo results for these observables in proton-proton collisions and discuss the impact of initial-state radiation and multi-parton interaction. Finally, I will discuss the potential obstacles in applying these observables in heavy ion collisions.

Tuesday, 03.15.2022, 2:00 PM PST (Special time)

Dr. You Zhou (NBI)

Host: Xin-Nian Wang

Multi-particle correlations for the new decade of QGP studies

Slide Youtube


Multi-particle correlations have been compelling tools to probe the properties of the Quark-Gluon Plasma (QGP) created in the ultra-relativistic heavy-ion collisions. In this seminar, I will present a generic recursive algorithm for multi-particle cumulants, which enables the calculation of arbitrary order multi-particle cumulants. Among them, I will emphasize a particular series of mixed harmonic multi-particle cumulants, which measures the general correlations between any moments of different flow coefficients. The study of these new multi-particle cumulants in heavy-ion collisions will significantly improve the understanding of the initial event-by-event geometry fluctuations and the hydrodynamic response in the final state. This will pave the way for more stringent constraints on the initial state and help extract more precise information on how the created hot and dense matter evolves. Last but not least, I will show the most recent study of correlations between anisotropic flow and mean transverse momentum in terms of multi-particle correlations/cumulants. I will show how we can directly access the initial conditions of heavy-ion collisions using the latest experimental measurements at the LHC and discuss the critical challenge of the state-of-the-art QGP studies via Bayesian analyses.


Tuesday, 03.08.2022, 2:00 PM PST

Dr. Giuliano Giacalone (Heidelberg University)

Host: Xin-Nian Wang

The initial state of the quark-gluon plasma: status, prospects, interdisciplinary connections

Slides Youtube


The hydrodynamic model of the quark-gluon plasma (QGP) formed in relativistic nuclear collisions has permitted us over the years not only to obtain quantitative estimates of the transport properties of this medium from data, but also to establish a phenomenologically viable picture of its initial condition and how it emerges from the interaction of two ions at high energy. I review the current understanding of the initial condition of the QGP, emphasizing the outcome of state-of-the-art models and the overall picture that they yield. I discuss the progress made in the definition of observable quantities that offer a specific sensitivity to the physics of the initial state, with a focus on recent results (both theoretical and experimental) on mean transverse momentum-anisotropic flow correlations. Such observables pose unprecedented constraints on the parameters of state-of-the-art Monte Carlo generators for nuclear collisions, demonstrating, in particular, the importance of having an accurate implementation of the structure of the colliding ions, and the nucleons therein, in such frameworks. Consequently, the initial state of heavy-ion collisions provides fertile ground for new interdisciplinary connections involving different aspects of hadronic and nuclear physics across energy scales.

Tuesday, 2022.02.22, 3:30 PM PST


Yi Yin (Quark Matter Research Center, Institute of Modern Physics (Chinese Academy of Science))

Host: Sooraj Radhakrishnan

Spin-momentum correlation in hot and dense QCD matter

Slides Youtube


The transport phenomena involving spin are instrumental in investigating quantum effects in many-body systems. In heavy-ion collisions, the recent measurement of spin polarization and spin alignment opens a new avenue to explore the properties of hot and dense QCD matter. Based on linear response theory and quantum kinetic equation, we have systematically studied spin-momentum correlation induced by hydrodynamic gradients [1]. In addition to the widely studied thermal vorticity effects, we identify an undiscovered contribution from the fluid shear [2]. This shear-induced polarization (SIP) can be viewed as the fluid analog of strain-induced polarization observed in elastic and nematic materials. The possible signature of SIP at RHIC and LHC will be elaborated. Then, I will present our prediction for the signature Spin Hall effect induced by baryon chemical gradient at RHIC beam scan energies [3,4]. If time permitted, I will briefly discuss the effect of SIP on vector mesons. .

Wednesday, 2022.02.015, 3:30 PM PST


Douglas Higinbotham (Jefferson Lab)

Host: Jennifer Rittenhouse West

Slides Youtube

The End of the Proton Radius Puzzle?


For many years scientists believed that the proton radius was 0.877(6) fm based on a series of atomic Lamb shift and electron scattering measurements. In 2010, a new type of measurement, making use of muonic hydrogen, determined the radius to be 0.842(1) fm. The large systematic difference between muonic hydrogen measurements and the previous results became known as the proton radius puzzle. To solve this puzzle, a world-wide theoretical and experimental investigation has been undertaken. I will review the status of the puzzle with an emphasis on electron scattering results and the systematic differences between the different analysis techniques that led to disparate conclusions. I will leave it to the audience to decide if the puzzle is solved.

Joint NT and HIT seminar (note special day and time)

Wednesday, 2022.02.02, 1:00 PM PST

Dr. Yong Zhao (Argonne National Lab)

Host: Aaron Meyer

Lattice QCD Determination of the Bjorken-$x$ Dependence of PDFs at Next-to-next-to-leading Order


Slides Youtube


The large-momentum effective theory (LaMET) is a systematic approach to calculate parton physics from Euclidean approaches such as lattice QCD. With major progress in the lattice renormalization and perturbative matching, the lattice calculation of PDFs with LaMET is now entering the stage of precision control. In this talk, I will present a state-of-the-art lattice QCD calculation of pion valence quark distribution with next-to-next-to-leading order matching correction, which is done using two fine lattices with spacings $a=0.04$ fm and $0.06$ fm and valence pion mass $m_\pi=300$ MeV at boost momentum as large as 2.42 GeV. I will demonstrate that perturbative matching in Bjorken-$x$ space yields a reliable determination of the valence quark distribution for moderate x with a target precision, which shows considerably improved systematic uncertainty compared to a previous analysis of the same lattice data with a short-distance factorization approach in the coordinate space, and is in excellent agreement with the most recent global analyses.

Tuesday, 2022.01.25, 3:30 PM PST

Prof. Rene Bellwied (University of Houston)

Host: Sooraj Radhakrishnan

Matter under extreme conditions - Particle Collisions along the QCD Phase Diagram


Slides Youtube

Relativistic particle collisions have come a long way during the past two decades with the characterization of states of matter along the QCD phase transition line. I will try to show how these discoveries lead to significant multi-disciplinary efforts to understand the creation and evolution of matter under extreme conditions. Examples that will be highlighted are the connection of fundamental quantum theories to collective phenomena and particle production, as well as astrophysical measurements that link to interactions observed at RHIC and LHC.

Tuesday, 2022.01.18, 3:30 PM PST

Prof. Tanja Horn (JLab & The Catholic University of America)

Host: Jennifer Rittenhouse West

PION AND KAON STRUCTURE FUNCTIONS


Slides Youtube


Pions and kaons are, along with protons and neutrons, the main building blocks of nuclear matter. They are connected to the Goldstone modes of dynamical chiral symmetry breaking, and appear to be key to the further understanding of the mechanisms that generate all hadron mass in the visible universe. The distribution of the fundamental constituents, the quarks and gluons, is expected to be different in pions, kaons, and nucleons. However, experimental data are sparse. As a result, there has been persistent doubt about the behavior of the pion's valence quark structure function at large Bjorken-x and virtually nothing is known about the contribution of gluons. Experiments at the 12 GeV JLab using hard scattering from the virtual meson of the nucleon will shed light on this by providing information on how emergent mass manifests in the wave function and about the quark-gluon momentum fractions. The Electron-Ion Collider (EIC) with an acceptance optimized for forward physics will enable a revolution in our ability to study pion and kaon structure. The unique experimental facilities at the EIC will provide access to structure functions over a wide range of kinematics. This would allow for measurements testing if the origin of mass is encoded in the differences of gluons in pions, kaons, and nucleons, and measurements that could serve as a test of assumptions used in the extraction of structure functions and the pion and kaon form factors. Measurements at an EIC would also allow to explore the effect of gluons at high x. In this talk we will discuss the status of measurements at Jefferson Lab and prospects of such measurements at the EIC.

Tuesday, 2022.01.11, 3:30 PM PST

Prof. Jiangyong Jia (SUNY Stony Brook)

Imaging nuclear structure in heavy-ion collisions

slides Youtube


The hydrodynamic modeling of the quark-gluon plasma (QGP) permits us today not only to perform quantitative extractions of the transport properties of the QGP, but also to strongly constrain its initial condition. A growing body of experimental evidence shows that the QGP initial condition is strongly impacted by the shape and radial structure of the colliding nuclei. We discuss the exciting prospect of using precision flow measurements as a tool to image the structure of atomic nuclei, and show how such measurements probe the quadrupole, octupole, and triaxial deformations of the colliding ions, as well as their neutron skin. Motivated by recent groundbreaking measurements from RHIC and LHC, we discuss in particular the case of collisions of isobaric nuclei, which provide the cleanest access route to the collective structure of the colliding ions. We discuss the implications of obtaining an information about the structure of nuclei from high-energy collisions that is fully complementary to that obtained in low-energy experiments, and argue that a scan of stable isobars at high-energy colliders may open a new exciting direction of research in nuclear physics.