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)

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

HIT zoom link 

Previous seminars can be viewed on our HIT Youtube Channel

Upcoming seminars

We hope everyone has a good holiday season and will be happy to welcome you back to our Hadron-Ion Tea Seminar Series in 2023!  All talks are 100% virtual except for local speakers (in-person & zoom) - we hope you join us!

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

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

Florian Jonas (University of Münster/ORNL)

Host: Peter Jacobs and Farid Salazar

"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.

Tuesday, February 7th 2023, 3:30 PM PST

Dr. Xiaoxuan Chu (Brookhaven National Lab)

Host: Farid Salazar

"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: Thursday, February 9, 2023, 3:30 PM PST

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.

Special date & time: Thursday, February 14, 2023, 10:30 AM PST

Dr. Yousen Zhang (Rice University)

Host: Peter Jacobs and Farid Salazar

"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.

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

Christopher Kane (University of Arizona)  

Host: All organizers

"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.

Thursday,  March 2, 2023  3:30 PM PST (in-person & zoom)

Dr. Agnieszka Sorensen (University of Washington)  

Host: Jennifer Rittenhouse West

"Physics with the STAR Collaboration"

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"

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

Dr. Jianwei Qiu (Jefferson Lab)  

Host: Farid Salazar 


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

Dr. Ian Moult (Yale University)  

Host: Wenqing Fan

"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.

Thursday,  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.

Tuesday,  April 11th, 2023  3:30 PM PST (in-person & zoom)

Dr. Gang Wang (UCLA)  

Host: Nu Xu

"Review of the Experimental Search for the Chiral Magnetic Effect in Heavy-ion Collisions"

The quark-gluon plasma created in high-energy heavy-ion collisions has been conjectured to exhibit a spontaneous electric-charge separation in the direction of a strong magnetic field through the chiral magnetic effect (CME). The experimental confirmation of the CME in heavy-ion collisions will uncover fundamental aspects of strong interaction physics such as the QCD chiral symmetry restoration and the topological configurations of non-Abelian gauge fields. Over the past two decades, experiments at RHIC and the LHC have performed a series of charge-separation measurements in A+A collisions at various beam energies from the center-of-mass energy of 5.02 TeV down to 7.7 GeV, and in different collision systems including p+Au, p+Pb, d+Au, Cu+Cu, Au+Au, Pb+Pb and U+U collisions, as well as the recent isobaric Ru+Ru and Zr+Zr collisions. Multiple analysis methods have also been developed to manifest the charge separation effect and suppress the flow related background. In this talk, I will review the aforementioned results, summarize our current understanding, and provide an outlook on future analyses.

Tuesday,  April 25th, 2023  3:30 PM PST (zoom)

Dr. Norbert Herrmann (Heidelberg University)  

Host: Nu Xu

"Physics Program in CBM Experiment at FAIR"