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: Shujie Li, Dimitra Pefkou, Nu Xu, & Wenbin Zhao

HIT zoom link 

Previous seminars can be viewed on our HIT Youtube Channel

Upcoming seminars

Welcome 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!

Thursday,  December 7th, 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.

Monday, December 11th, 3:30 PM (in-person & zoom)

Dr. Raju Venugopalan (BNL)

Host: Dimitra Pefkou

"Universal features of  high energy scattering in QCD and gravity from shockwave collisions"

We discuss a remarkable double copy relation (discovered 40 years ago by Lev Lipatov) of  multi-particle (2-> N) amplitudes in Einstein gravity to their QCD counterpart. We demonstrate [1] that the results of Lipatov's  Feynman diagram computations can be recovered by comparing the inclusive gluon spectrum produced in shockwave collisions in QCD to the inclusive gravitational wave spectrum produced in shockwave collisions in Einstein gravity. We discuss the potential implications of this correspondence both for next-generation measurements of gravitational wave radiation in close Black Hole encounters and for a quantum picture of Black Holes as over-occupied graviton states [2]. The latter description points in turn to a deeper (universal) understanding of gluon shockwaves as Goldstone modes of a broken 

global symmetry; their decay in shockwave collisions leads to quark-gluon plasma formation. We discuss the potential implications of this picture for precision computations at the Electron-Ion Collider. 


[1] Himanshu Raj and Raju Venugopalan, arXIv:2311.03463

[2] Gia Dvali and Raju Venugopalan, arXiv:2106.11989, Phys. Rev. D105, 056026 (2022). 

Tuesday, December 12th, 2023, 3:30 PM PST (in-person & zoom) 

Dr. Peter Jacobs (LBL)

Host: Wenbin Zhao

"Low-x evolution at the LHC and EIC: the ALICE FoCal upgrade"

Non-linear evolution of the gluon density of matter at low-x ("gluon saturation") is a natural consequence of the non-Abelian nature of QCD, but quantitative understanding of it remains elusive. The observation and quantification of non-linear evolution would be a major milestone in Nuclear Physics, and its search is a central component of the EIC scientific program. The same QCD forward scattering amplitudes probe saturation effects in both e+A DIS at the EIC and forward p+A at the LHC, providing the opportunity to extend the reach in low-x in this search far beyond the range accessible at the EIC. In this talk I first briefly review the current status of forward QCD measurements at the LHC. I will then discuss the ALICE FoCal ("Forward Calorimeter") upgrade planned for the end of the decade, which will provide incisive measurements of direct photons, neutral and vector mesons, jets, and their correlations, in hadronic and ultra-peripheral pp and p+Pb collisions at forward rapidities, which probe the gluon density down to x~10^-6. Finally, I will discuss a broader strategy for comprehensive analysis of EIC and forward RHIC and LHC data to constrain the low-x gluon distribution.

Thursday, December 14th, 10 AM  (zoom)

Dr. Eric Voutier (Université Paris-Saclay)

Host: Shujie Li

The Jefferson Lab Positron Program

The perspective of high duty-cycle and high intensity polarized and unpolarized positron beams, in complement to the existing CEBAF (Continuous Electron Beam Accelerator Facility) 12 GeV electron beams, has been nurtured since the very first 6 GeV upgrade of the CEBAF accelerator. Along the years, experimental results about the electromagnetic form factors and the generalized parton distributions of the nucleon pointed towards the importance of positron beams for the experimental determination of these fundamental quantities of the nucleon structure. Further ideas emerged about testing the predictions of the standard model, exploring the dark matter sector, or investigating nucleon structure with electroweak processes. A long term and comprehensive research effort has developed both in the physics [1] and the technics [2] areas to assess the potential of an experimental program and to address the technological issues of high duty cycle positron beams. The Jefferson Lab Program Advisory Committee recognized the high scientific value of such a program. The development of positron beam capabilities at Jefferson Lab (JLab) is identified as the first step of a future CEBAF upgrade.

This seminar will review the current status of the JLab positron physics program with a specific focus on Two Photon Exchange effects and the study of Generalized Parton Distributions. The several technical challenges raised by the development of continuous polarized positron beams will be also addressed.

[1] (JLab Positron Working Group) A. Accardi et al. Eur. Phys. J. A 57 (2021) 261.

[2] (Ce + BAF Working Group) J. Grames et al. JACoW IPAC (2023); arXiv/physics.acc-ph:2309.15581.

TBD Fall 2023

Dr. Holly Szumila-Vance (Jefferson Lab)

Host: Shujie Li

"The Search for Color Transparency"

Coming soon!


Dr. Julie Roche (Ohio University)

Host: Shujie Li

The upcoming GPD measurements with the neutral particle spectrometer at JLab

Coming soon!