Previous HIT Seminars

Tuesday,  March 21, 2023  3:30 PM PST (zoom)

Dr. Jihee Kim (Argonne)  

Host: Jennifer Rittenhouse West

"Design Concept of Imaging Barrel Electromagnetic Calorimeter for the Electron-Ion Collider"

The Electron-Ion Collider (EIC) will be an experimental facility to explore the gluons in nucleons and nuclei, shedding light on their structure and the interactions within. Physics goals, detector requirements, and technologies at the EIC are outlined and discussed in the EIC community White Paper and Yellow Report. In particular, for the barrel electromagnetic calorimetry, the electron energy and shower profile measurements play a crucial role in the separation of electrons from background pions in deep inelastic scattering processes. Moreover, the calorimeter must measure the energy and position of photons, identify single photons originating from deeply virtual compton scattering process, and photon pairs from pi^0 decays. Based on detector requirements, we propose a design of the imaging barrel electromagnetic calorimeter. It is a hybrid design utilizing imaging calorimetry based on monolithic silicon sensors (AstroPix) and scintillating fibers embedded in Pb.  We have studied the proposed calorimeter in detail through realistic simulations to test it against the requirements for the physics case described in the EIC community Yellow Report. In this talk, I will present the expected calorimeter performance based on simulations with 3T magnetic field and the outlook of the upcoming R&D program related to the imaging calorimetry will be also presented.

Special date & room - same time!

Thursday,  March 16, 2023  3:30 PM PST (in-person & zoom) Room 70-191 

Dr. Ian Moult (Yale University)  

Host: Wenqing Fan

Slides Youtube

"Conformal Colliders Meet the LHC"

Jets of hadrons produced at high-energy colliders provide experimental access to the dynamics of asymptotically free quarks and gluons and their confinement into hadrons. Motivated by recent developments in conformal field theory, we propose a reformulation of jet substructure as the study of correlation functions of a specific class of light-ray operators and their associated operator product expansion (OPE). We show that multi-point correlation functions of these operators can be measured in real LHC data, allowing us to experimentally verify properties of the light-ray OPE. We then discuss how this reformulation provides new ways of experimentally studying QCD at colliders, as well as new theoretical techniques for performing previously intractable calculations.

Tuesday,  March 14th, 2023  3:30 PM PST (zoom)

Slides Youtube

Dr. Jianwei Qiu (Jefferson Lab)  

Host: Farid Salazar 

"Exclusive hard processes for extracting Generalized Parton Distributions"

The Generalized Parton Distributions (GPDs) describe the distribution of quarks/gluons inside a colliding hadron in both longitudinal partonic momentum fraction $x$ and transverse space (“tomographic images”).  Their moments of the momentum fraction $x$ provide critical information on partonic angular momentum contribution to the hadron spin and gravitational form factors of the hadron.  Extracting GPDs reliably from experimental measurements has been a major science goal for studying QCD and hadron physics.  However, conventional exclusive processes such as deeply-virtual Compton scattering (DVCS) cannot fully disentangle the longitudinal dependence and provide the tomographic images at fixed x.  In this talk, I will introduce a class of exclusive hard processes, to be referred as single diffractive hard exclusive processes (SDHEP), for the extraction of GPDs.  I will discuss the necessary and sufficient conditions for SDHEP to be factorized in terms of GPDs.  I will also demonstrate that SDHEP is not only sufficiently generic to cover all known processes for extracting GPDs, but also well-motivated for the search of new processes for the study of GPDs.  Finally, I will carefully examine the sensitivity of SDHEP to the parton momentum fraction $x$ dependence of GPDs.

Tuesday,  March 7th, 2023  3:30 PM PST (in-person & zoom)

Dr. Haiyan Gao ( BNL and Duke University )  

Host: Shujie Li 

"Physics Program with SoLID"

The Solenoidal Large Intensity Device (SoLID) is a new experimental apparatus proposed for Hall A at the Thomas Jefferson National Accelerator Facility (JLab). SoLID will combine large angular and momentum acceptance with the capability to handle high data rates at large luminosity. As such SoLID will push JLab to a new limit at the QCD intensity frontier to exploit the full scientific potential of the 12-GeV CEBAF. The slate of approved high-impact experiments consists of the tomography of the nucleon in 3-D momentum space from Semi-Inclusive Deep Inelastic Scattering, expanding the phase space in the search for new physics and novel hadronic effects from parity-violating Deep Inelastic Scattering, a precision measurement of near-threshold J/psi production to probe the gluon field and its contribution to the proton mass, and more. In this talk, I will discuss the rich SoLID physics program and the proposed apparatus.

Change in time & location:

Thursday,  March 2, 2023  1 PM PST (in-person & zoom) Nuclear theory seminar room!

Slides Youtube

Dr. Agnieszka Sorensen (University of Washington)  

Host: Jennifer Rittenhouse West

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

The equation of state (EOS) of dense nuclear matter can give insights into fundamental properties of QCD: among others, it can elucidate phases of matter in different regions of the QCD phase diagram, it can help explain the structure of both neutron stars and neutron-rich nuclei, and it can inform us about the nature of the underlying fundamental interactions. In experiments colliding heavy nuclei at relativistic velocities, the EOS is probed through observables describing the collective behavior of the produced matter, such as flow observables, the dependence of which on the EOS can be studied in simulations.  In this talk, I will discuss recent progress on constraining the EOS with hadronic transport simulations, used to model heavy-ion collision experiments at intermediate energies. I will highlight results from a recent Bayesian analysis study using new data from RHIC, and I will discuss the findings in the context of other known constraints from heavy-ion collisions and neutron star studies. I will also outline developments in state-of-the-art hadronic transport codes necessary to fully utilize the potential of the forthcoming wealth of data from the BES-II FXT program at RHIC, from GSI and FAIR, as well as from FRIB and future FRIB400.

Tuesday,  February 28th, 2023  3:30 PM PST (in-person & zoom)

Christopher Kane (University of Arizona)  

Host: Christian Bauer, Farid Salazar

Slides Youtube

"Overcoming exponential volume scaling in quantum simulations of lattice gauge theories"

Quantum computers hold the promise of overcoming the numerical sign problem and allowing for study of the dynamics of quantum field theories from first principles. Before performing such calculations, it is important to ensure that the quantum algorithms used do not have a cost that scales exponentially with the volume. In this talk, I will discuss an interesting test case: a formulation of compact U(1) gauge theory in 2+1 dimensions free of gauge redundancies. A naive implementation onto a quantum circuit has a gate count that scales exponentially with the volume. I will discuss how to break this exponential scaling by performing an operator redefinition that reduces the non-locality of the Hamiltonian. With the exponential volume scaling broken, I will then show how the gate count scaling with the volume can be further reduced by approximating the quantum circuit without introducing large errors.

New Special time: Tuesday, February 14, 2023, 9:30 AM PST (Zoom)

Dr. Yousen Zhang (Rice University)

Host: Peter Jacobs and Farid Salazar
Slides and Recording available upon request to organizers

"Probing QCD matters using heavy flavor quarks at the LHC"

Quark gluon plasma created in relativistic heavy ion collisions is a novel state in which partons are deconfined from normal matter in the universe. It is characterized by the shocking collectivity of QGP and energy loss of high energy particles traversing through QGP. Recent measurements show that the collectivity can also emerge in high-multiplicity proton-proton and proton-nucleus collisions, which was originally believed to only exist in large ion collisions. However, the origin of these collective motions is still a puzzle in theoretical studies mainly debating on contributions from initial correlations and in-medium effects. Heavy flavor quarks are sensitive to both the initial stage conditions and the later-on in-medium effects of collisions, thus can provide important information for understanding the inner workings of QGP in large ion collisions and the origin of the collectivity in small systems. In this talk, I will present the recent progress of heavy flavor collectivity at the LHC from large to small colliding systems, and discuss the future opportunities with the high-luminosity LHC together with the CMS detector upgrades.

Special time: Thursday, February 9, 2023, 2:00 PM PST (Zoom)

Dr. Nicole Lewis (Brookhaven)

Host: Peter Jacobs and Shujie Li


"Baryon Stopping in Photonuclear Collisions"

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

Tuesday, February 7th 2023, 3:30 PM PST (Zoom)

Dr. Xiaoxuan Chu (Brookhaven National Lab)

Host: Farid Salazar

Slides Youtube

"Probing nonlinear gluon dynamics at RHIC and the EIC"

The gluon distribution function grows with lower and lower momentum fraction very fast. As the total scattering cross section is bound by quantum mechanics, the raise of the gluon density has to be tamed, which is explained by gluon recombination under the color glass condensate (CGC) framework. A definitive discovery of nonlinear effects in QCD and as such the saturation regime would significantly improve our understanding of the nucleon structure and of nuclear interactions at high energy. Two particle azimuthal correlation is one of the most direct and sensitive channels to access the underlying nonlinear gluon dynamics. In this talk, we will present the recent results of forward di-hadron correlations measured at RHIC, together with the signatures of gluon saturation predicted by CGC. New opportunities for measurements with the STAR forward upgrade and future EIC to study the nonlinear effects in QCD will also be discussed.

Special date & time: Thursday, February 2, 2023, 10:30 AM PST (Zoom) 

Florian Jonas (University of Münster/ORNL)

Host: Peter Jacobs and Farid Salazar

Slides and Recording available upon request to organizers

"Prompt photon production: probing gluons in protons and nuclei at hadron colliders"

Measurements of prompt photons at hadron colliders offer unique insights into the substructure of the colliding projectiles, enabling constraints of so called Parton Distribution Functions (PDFs), which encode the inner structure of the hadron in a universal parametrization.

In particular, prompt photons are sensitive to the gluon distributions, which are one of the least constrained PDFs and not directly accessible via deep inelastic scattering.

Furthermore, studies of the gluon bound inside protons (and nuclei) are of key importance for the exploration of non-linear QCD, where in particular their low-x growth is expected to be tamed by gluon saturation.

Photons do not interact via the strong interaction, which makes them a particularly robust probe, carrying information from the initial hard scattering to the detector, unaffected by any final state effects commonly encountered in large collision system.

This talk outlines the key experimental techniques and challenges arising in isolated prompt photon measurements. An overview of the currently available experimental results at the LHC and their impact on the gluon PDF is followed by a look into the future, outlining how prompt photon measurements at hadron colliders with the ALICE Forward Calorimeter can play an important role in the search for gluon saturation and complement DIS measurements at the EIC.

Special seminar on Wednesday:

Wednesday, January 18th, 2023, 3:30 PM PST 

Dr. Xiaohui Liu (Beijing)

Host: Jennifer Rittenhouse West


"Nucleon Energy Correlators for the Color Glass Condensate"

An invited talk and discussion on very recent work by Xiaohui Liu, Feng Yuan and collaborators on low-x physics, specifically a new method to access gluon saturation which is highly relevant for the future Electron-Ion Collider.  All welcome, and please note this will be a pedagogical seminar with a combination of slides and whiteboard, particularly aimed toward early career people who might not be familiar with the physics. 

Tuesday, January 17th, 2023, 3:30 PM PST 

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.

Tuesday, January 10th, 2023, 3:30 PM PST (in-person & zoom)

Dr. Joao Barata (BNL)

Host: Farid Salazar/Xin-Nian Wang

Jet evolution in anisotropic plasmas

Slides Youtube

 Over the last decades, the heavy-ion collisions at RHIC and the LHC allowed the exploration of QCD at high energies and densities. In these experiments, the nuclear matter is produced far from equilibrium, and undergoes a multiphase evolution until it thermalizes into a nearly ideal liquid: the quark-gluon plasma (QGP). The main effort of the heavy-ions community is focused in extracting the detailed properties of this phase of matter. Among the many probes used for this effect, QCD jets have proven to be able to explore the quark gluon plasma at different time and length scales, providing a differential and dynamical picture for the underlying matter. Nonetheless, a theoretical treatment of jet structure which is sensitive to the details of the QGP is still far from complete. In this talk, I will present some recent work on how to describe jet evolution in the presence of anisotropic matter. First, I will detail the basic modifications necessary to make to the standard jet quenching formalism. Afterwards, I will show that the QGP anisotropies can be taken into account to arbitrary order in a gradient expansion using an effective kinetic theory approach. Remarkably, at second order in the matter gradients, we find a novel master equation which generalizes the usual Boltzmann transport. Finally, I will discuss how such effects can be manifest at the level of jet observables.

Thursday, December 15th, 2022  3:30 PM PST (zoom)

Dr. Alba Soto-Ontoso (CERN)

Host: Farid Salazar

"Better parton showers for HL-LHC and beyond"

Slides Youtube 

The Large Hadron Collider is currently running at its highest energy and luminosity. In order to maximally exploit the potential of this precise dataset to uncover physics beyond the Standard Model, it is of crucial importance to develop tools that faithfully characterise the QCD background. Parton showers lie at the core of general purpose Monte Carlo event generators. They aim at correctly describing the phase-space for QCD branchings across disparate energy scales. A natural question, largely overlooked in the literature, is up to which degree of logarithmic accuracy do parton showers meet this goal. In this talk, I will introduce recent efforts by the PanScales collaboration to establish the criteria that a parton shower should satisfy in order to reach a given logarithmic accuracy. Then, I will present the design and implementation of next-to-leading logarithmic accurate parton showers both in electron-positron annihilation and hadron collisions. I will conclude with some exploratory studies about the phenomenological impact of these highly-precise showers.

Tuesday, December 13th, 2022  3:30 PM PST (zoom)

Dr. Allison Zec (UNH)

Host: Jennifer Rittenhouse West

"Achieving High Deuteron Tensor Polarization To Probe Nuclear Structure"


Advances in experimental technology have allowed for new high-luminosity scattering probes on highly spin polarized nuclear targets. These developments have made it possible to probe the structure of tensor-polarized deuterium with greater precision than ever before. Two experiments, approved to run in Jefferson Lab's experimental hall C will measure two deuteron tensor observables. The first experiment will probe the deuteron tensor structure function b1 in the x<1 deep inelastic region, and the second experiment will measure the deuteron tensor asymmetry Azz in the quasielastic region. In order to achieve a high tensor polarized deuteron target, developments are being made in nuclear polarization technology using the dynamic nuclear polarization (DNP) technique. DNP is used to enhance the nuclear spin polarization of materials. DNP works by using microwaves to continuously drive spin transitions in a material that is doped with free radicals and placed inside a 1 K environment in a high magnetic field. Further tensor polarization enhancement is achieved using additional RF saturation on the target magterial. Once enhanced, the nuclear polarization can be determined by analyzing the lineshape of the NMR absorption spectrum. This talk will describe the DNP system used at the University of New Hampshire, and explain novel techniques in inducing high tensor polarization in deuterium.

Tuesday, November 29th, 2022  3:30 PM PST (zoom)

Dr. Jochen Klein (CERN, zoom)  

Host: Nu Xu

"Physics Program and Detector Development with ALICE3"

Slides     Youtube

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.

Tuesday,  November 15th, 2022  10 am PDT (special time )  (zoom)

Dr. Tommaso Giani (NIKHEF Amsterdam) 

Host: Shujie Li  

"Evidence for Intrinsic Charm Quarks in the Proton"

Slides      Youtube

It has been argued for a long time that the proton could have a sizable intrinsic component of the charm quark.

I will discuss how to disentangle the intrinsic charm component from charm-anticharm pairs arising from high-energy radiation and present results providing evidence for intrinsic charm, by exploiting the NNPDF4.0 high-precision determination of proton Parton Distribution Functions. The existence of intrinsic charm is estabilished at the 3σ level, with a momentum distribution in remarkable agreement with model predictions. Finally I will discuss how these findings are supported by the very recent data on Z-boson production with charm jets from the LHCb experiment.

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

Dr. Misha Stephanov (UIC)

Host: Nu Xu

"Predicting randomness in relativistic hydrodynamics"

Slides    Youtube

We usually think of hydrodynamics as a deterministic description of fluid motion. The focus of this talk is on random fluctuations in fluids caused by thermal noise, inherent in systems with dissipation. The interest in this subject is driven by the progress of heavy-ion collision experiments towards the mapping of the QCD phase diagram. In particular, the search for the QCD critical point at RHIC requires quantitative understanding of fluctuations and their dynamics. I will discuss the role of the fluctuations in hydrodynamics and how we can predict their evolution using deterministic equations.

Photo credit: Jessica Rotkiewicz

Tuesday, November 8th, 2022, 3:30 PM PDT (Zoom only)

Dr. Björn Schenke (BNL)

Host: Farid Salazar

"QCD at the Crossroads: Hot QCD Town Hall meeting summary"

Slides Youtube

In this talk, I will try to summarize the discussions/presentations at the QCD town meeting, Boston, September 23-25:

Tuesday, November 1st, 2022, 3:30 PM PDT

In-person (Theory Lounge 70-228) & Zoom

Dr. Feng Yuan (LBNL)

Host: Nu Xu/Farid Salazar

"QCD at the Crossroads:  Cold QCD Town Hall meeting summary"

In this talk, I will try to summarize the discussions/presentations at the QCD town meeting, Boston, September 23-25:

Tuesday, October 25, 2022, 3:30 PM PDT

In-person (Theory Lounge 70-228) & Zoom

Dr. Tyler Hague (LBNL)

Host: Shujie Li/Jennifer Rittenhouse West

"The EMC Effect: Light Nuclei are Weird" 

Slides Youtube

In 1983, the European Muon Collaboration (EMC) recorded Deep-Inelastic Scattering data on Iron, Deuterium, and Hydrogen. Comparisons of the targets noted that the quark structure of nucleons is modified by the surrounding nuclear environment, dubbed the EMC Effect. Nearly 40 years later, the community is still working to understand the mechanism behind this. Initial studies of the EMC Effect on heavy nuclei were able to paint broad strokes pictures of how the effect scales across nuclei. However, later precision tests of light nuclei were found to be in tension with these previous understandings. Key missing pieces to understanding this are the free neutron structure function and nuclear effects. The MARATHON experiment used a novel technique to extract F2n/F2p by largely canceling nuclear effects in the A=3 mirror nuclei in the yield ratio. In this talk, I will give an overview of our current knowledge of the EMC Effect followed by a discussion of the MARATHON experimental results and recent work applying these to light nuclei to understand nuclear effects.


Thursday, October 20th,   2022  3:30 PM PDT 

In-person (Theory Lounge 70-228) & Zoom

Mr. Henry Klest  (Stony Brook University)
Host: Nu Xu

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

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.

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

Slides Youtube

   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.

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

Dr. Yoshitaka Hatta (BNL)

Host: Farid Salazar

Spin Physics Opportunities at the EIC
Slides Youtube

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.

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?



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


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


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.