General information:

1. The seminar usually takes place in person at Knudsen 5-142 and sometimes via Zoom.
2. We also actively participate in seminars offered by the Nuclear Science Division at Lawrence Berkeley National Laboratory: Hadron Ion Tea (HIT).
3. For travel information, including flights, directions, and parking, please visit our Visiting page.
4. For seminars in previous years, please refer to:

2024 | 2023 | 2022 | 2021 | 2020 | 2019 | 2018 | 2017

11/12/2025

Onset of Bjorken flow in a quantum many-body simulation of the massive Schwinger model

Shuzhe Shi, Tsinghua University
3:00 PM Wednesday, Knudsen 5-142

The onset of hydrodynamics in the hot medium created in relativistic heavy-ion collisions is a crucial theoretical question. A first-principle simulation requires a real-time, non-perturbative calculation of the quantum system. In this work, we perform such simulations using the tensor network method, which enables large-scale quantum many-body simulations by retaining only the most essential quantum states for collective behaviors. We focus on the massive Schwinger model, a low-dimensional analog of quantum chromodynamics (QCD), as they share important properties such as confinement and chiral symmetry breaking. Starting from an initial state that puts a localized excitation atop the vacuum and mimics the energy deposition from colliding nuclei, we observe hydrodynamic behavior consistent with Bjorken flow in all relevant degrees of freedom: energy density, fluid velocity, and bulk pressure. The time scale for hydrodynamic onset aligns with the thermalization time of the quantum distribution function. This simulation provides a controllable tool to test microscopic theories of hydrodynamics in a strong-coupling quantum system.

10/31/2025

Simulating Particle Scattering with Digital Quantum Computers

Yahui Chai, DESY
10:00 AM Friday, Knudsen 5-142

Particle scattering is a cornerstone of high-energy physics, providing deep insights into the structure of matter. However, simulating this real-time, nonperturbative dynamic process remains a major challenge for classical methods: Monte Carlo techniques suffer from sign problems, while tensor network approaches are limited by rapid entanglement growth. Quantum computing offers a promising path to overcome these barriers. In this talk, I will first present our work on meson scattering in a (1+1)-dimensional Z2 lattice gauge theory. We develop an efficient method to construct meson creation operators using the quantum subspace expansion (QSE), enabling the excitation of high-fidelity eigenstates with well-defined momenta. Meson wave packets are then built from these operators and prepared by quantum circuits with O(L) depth, with L the system size. The subsequent real-time dynamics are simulated using Trotterized quantum circuits. By the classical simulation, we observed both elastic and inelastic scattering processes with rich physical phenomena, including the new particle production, entanglement entropy growth, and longer flux string generation and breaking. In the second part, I will introduce our recent hardware implementation of fermion scattering in the (1+1)D Thirring model on IBM quantum devices with 40 and 80 qubits. By combining tensor-network-based circuit optimization with error mitigation techniques, we obtain experimental results that closely match ideal simulations, clearly capturing transmitted and reflected scattering behavior. Together, these results demonstrate the feasibility and scalability of quantum approaches to particle scattering, and point toward broader applications in lattice gauge theory and real-time quantum dynamics.

10/17/2025

Entanglement entropy and its imprint in DIS hadron multiplicity distributions

Martin Hentschinski, Universidad de las Américas Puebla
10:00 AM Friday, Knudsen 5-142

Entanglement entropy has emerged as a novel tool for probing QCD phenomena. In this talk I present recent results in describing hadron production in Deep Inelastic Scattering of electrons on protons. I will present our recent results on entanglement entropy in diffractive reactions and aspects of QCD evolution of entanglement entropy as well as the special role of soft gluons for successfully describing hadronic entropy.

10/10/2025

Seeing Color Confinement with Energy Correlators

Yu Jiao Zhu, Max Planck Institute for Physics, Germany
10:00 AM Friday, Knudsen 5-142

In this talk, I will introduce the idea of probing QCD non-perturbative dynamics through the lens of energy correlators, with a focus on their role in TMD dynamics, spectator fragmentation, and multi-Regge kinematics (MRK). I will also highlight the advantages of this approach compared to conventional q_T or jet-based measurements. See references: arXiv:1611.10329, 2509.01652, 2509.17596.

09/22/2025

Probe the proton gravitational form factors via near-threshold heavy quarkonium photo-production

Yuxun Guo, LBNL
11:00 AM Monday, Knudsen 5-142

Understanding the mass, spin, and mechanical properties of the nucleon has been one of the central topics in the field the nuclear physics. The generalized parton distributions (GPDs) and gravitational form factors (GFFs) have therefore drawn rising interest in recent years for such a purpose. In this talk, I will discuss how the GFFs can be studied with near-threshold heavy quarkonium photo-production. In particular, I will discuss the recent progress in promoting to next-to-leading order perturbative accuracy and implementing Bayesian inference method in the analysis. I will also present some recent developments in the global analysis of GPDs. These works mark an important step towards deciphering the multi-dimensional structures of the proton, which is one of the key physical motivations of the experiment programs at Jefferson Lab and future Electron-Ion Collider.

06/27/2025

Exploring Quantum Advantages in Optimization: Theory and Practice

Leo Zhou, UCLA
11:00 AM Friday, Knudsen 5-142

Optimizing a function over many variables is a fundamental problem with countless applications. Although we hope a quantum computer can help us solve this problem faster than classical computers, we have a very limited understanding of where a quantum advantage may be found. In this talk, I will present some recent theoretical and experimental advances that shed light on quantum advantages in this domain. First, I describe rigorous analyses of the Quantum Approximate Optimization Algorithm (QAOA) applied to various combinatorial optimization problems. For certain families of problems, we find the QAOA has a quantum advantage over the best known classical algorithms. Then, I will recount an experimental investigation of variational quantum algorithms for maximum independent set problems. Using a hardware-efficient encoding in 2D Rydberg atom arrays with up to 289 qubits, we systematically explore a class of graphs with programmable connectivity. On the hardest graphs, we observe a superlinear quantum speedup over classical simulated annealing in the deep circuit regime and analyze its origins.

06/26/2025

Neural network enhanced Bayesian analysis of heavy-ion observables

Henry Hirvonen, Vanderbilt University
11:00 AM Thursday, Knudsen 5-142

Bayesian statistical analysis is nowadays a well-established method for performing global fits of QCD matter properties and initial conditions to experimental data from ultrarelativistic heavy ion collisions. However, even when surrogate models such as Gaussian process emulators are used to reduce the number of simulations, the computational costs can still remain prohibitively large for producing sufficient training data for observables, such as rare flow correlators, which require a very large sample of events. These costs can be reduced by orders of magnitude by using neural networks to predict simulated event-by-event observables, whose event averages are then used in the training of the Gaussian process emulators. Here, the statistical analysis is enhanced with deep convolutional neural networks, which are trained to predict the model output event-by-event for a given initial state profile, QCD matter properties, and freeze-out conditions. This combination of neural networks and Gaussian process emulators reduces the computational cost of the analysis and allows us to account for the statistics-expensive flow observables that provide further constraints for the temperature dependencies of shear and bulk viscosity.

06/23/2025 - 06/25/2025

2025 SURGE Collaboration Meeting and Workshop

Physics and Astronomy Building, Conference Room 4-330

05/27/2025

Status of Intrinsic Charm

Ramona Vogt, LLNL/UC Davis
10:30 AM Tuesday, Knudsen 5-142

A nonperturbative charm production contribution, known as intrinsic charm, has been speculated since the 1980s. While it has yet to be satisfactorily proven, there have been recent tantalizing hints. Several experiments, either taking data or planned, could provide definitive evidence in the next few years. Recent experiments that have taken J/Psi and D meson data include SeaQuest at Fermilab and SMOG at LHCb. Future experiments such as NA60+ are in an energy regime where the intrinsic charm quark signature could be large and unmistakable. In this talk, the status of intrinsic charm is reviewed and model comparisons are made to available data, see also [1-4].

[1] R. Vogt, Limits on Intrinsic Charm Production from the SeaQuest Experiment, Phys. Rev. C 103 (2021), 035204.
[2] R. Vogt, Contribution from Intrinsic Charm Production to Fixed-Target Interactions with the SMOG Device at LHCb, Phys. Rev. C 108, 015201 (2023).
[3] R. Vogt, Energy dependence of intrinsic charm production: Determining the best energy for observation, Phys. Rev. C 106 (2022) 025201.
[4] R. Vogt, Tetraquarks from intrinsic heavy quarks, Phys. Rev. D 110, 074036 (2024).

05/23/2025

Toward simulations of QCD using qubits and qumodes

Felix Ringer, Stony Brook University
12:00 PM Friday, Knudsen 5-142

The strong force in nature, described by the theory of quantum chromodynamics (QCD), governs the interaction of quarks and gluons, which constitute the main building blocks of the visible universe. Since its development over five decades ago, various fundamental questions have remained unanswered despite significant theoretical and experimental efforts: How do the dynamics of quarks and gluons give rise to emergent structures such as nucleons and nuclei? What is the phase diagram of nuclear matter and what are the real-time and non-equilibrium dynamics at collider experiments and in the early universe? While significant progress has been made on the theory side using perturbative techniques and lattice QCD, the answers to some of the most challenging questions are beyond the capabilities of classical computing. Advances in quantum computing coupled with the development of innovative algorithms motivate the exploration of quantum simulations to address these questions. In this talk, I will discuss recent progress toward quantum simulations for fundamental particle and nuclear physics covering both discrete (qubit) and continuous variable (qumode) approaches.

05/14/2025

Hydrodynamical response on the celestial sphere

Joao Barata, CERN
12:00 PM Wednesday, Knudsen 5-142

The application of light-ray operators and their respective correlation functions has shed new light onto the properties of QCD at high energies. In the context of relativistic heavy ion collisions, these operators might allow to better pin point the properties of the underlying QCD bulk matter produced during these events. In this talk, I will discuss how the emergent medium produced in heavy ion collisions imprints into N-point energy correlators. In particular, I will discuss the contributions from perturbative branchings associated to the jet cascade and the energy outflow from the medium response due to the jet. I will argue that these different sources leave similar imprints in the observables in the collinear limit, and discuss how one could go further to disentangle them in experiment.

03/21/2025

New Phases and a Critical Point in Dense Nuclear Matter: Revelations from Comparisons of Dynamic Simulations to Heavy-Ion Collisions

Agnieszka Sorensen, Michigan State University
1:30 PM Friday, Knudsen 5-142

Uncovering the phase diagram of quantum chromodynamics (QCD) is at the heart of numerous theoretical, experimental, and observational efforts worldwide. Prominent efforts include studies aiming to identify the location of the QCD critical point (CP) or understand the apparent peak in the speed of sound in high-density nuclear matter. In pursuing these goals, relativistic collisions of heavy nuclei provide unique opportunities for probing hot and dense systems and studying the QCD equation of state (EOS). Recent and upcoming results from the Beam Energy Scan at the Relativistic Heavy Ion Collider (RHIC), given its extraordinary range of available collision energies which can probe systems with vastly different properties, are especially promising. Interpretation of the experimental observables across the RHIC energy range, necessary for uncovering the QCD phase diagram, has been an inspiring challenge for both experiment and theory. In this talk, I will summarize recent advancements in using experimental data and simulations of heavy-ion collisions to put constraints on the QCD EOS and support the search for the QCD CP.

02/25/2025

$\alpha_s$ Fits From Heavy Jet Mass

Arindam Bhattacharya, Harvard University
11:00 AM Tuesday, Knudsen 5-142

A global fit for $\alpha_s(m_Z)$ is performed on available $e^+e^-$ data for the heavy jet mass distribution. The state-of-the-art theory prediction includes $\mathcal{O}(\alpha_s^3)$ fixed-order results, N$^3$LL$^\prime$ dijet resummation, N$^2$LL Sudakov shoulder resummation, and a first-principles treatment of power corrections in the dijet region. Theoretical correlations are incorporated through a flat random-scan covariance matrix. The global fit results in $0.1145^{+0.0021}_{-0.0019}$, compatible with similar determinations from thrust and $C$-parameter. Dijet resummation is essential for a robust fit, as it engenders insensitivity to the fit-range lower cutoff; without resummation the fit-range sensitivity is overwhelming. In addition, we find evidence for a negative power correction in the trijet region if and only if Sudakov shoulder resummation is included.

02/19/2025

Unraveling the Standard Model with Precision at the Collider Frontier

Kyle Lee, MIT
2:00 PM Wednesday, Knudsen 5-142

Recent advancements in precision techniques—including those emerging from scattering amplitude research—have revolutionized our theoretical understanding of the Standard Model. At the same time, translating these breakthroughs into measurable collider observables calls for innovative methodologies. In this talk, I will highlight key areas of my research that bridge precision calculations and experimental data. My work addresses enduring challenges in the Standard Model, from unraveling the puzzle of hadronization and exploring the intrinsic and emergent scales of QCD to pushing the frontiers of precision predictions with the prospect of discovering new physics. I will also discuss how these approaches are being applied at current high-energy colliders like the LHC, RHIC, and EIC.

02/05/2025

Unlocking the mysteries of dark matter and neutrinos with a Deep Underground Liquid Xenon Observatory

Jianglai Liu, Shanghai JiaoTong University and T.D. Lee Institute
2:00 PM Wednesday, Knudsen 5-142

Dark matter and neutrinos are elusive, neutral components of the Universe that continue to intrigue us. Is dark matter composed of fundamental particles? How does it interact with ordinary matter? Are neutrinos their own antiparticles? Despite decades of dedicated research, these questions remain unanswered. Over the past two decades, ultra-low-background liquid xenon detectors have emerged as a highly promising technology for probing these mysteries. The PandaX (Particle and Astrophysical Xenon) experiment, located in the China Jinping Underground Laboratory beneath 2,400 meters of rock, is at the forefront of global efforts. Recently, the PandaX-4T detector achieved a significant milestone: a first glimpse of solar neutrinos elastically scattering off xenon nuclei, known also as a part of the "neutrino fog" in dark matter detections. In this talk, after an overview of this field, I will provide an overall picture of the PandaX experiment, highlight recent findings, and discuss future prospects for this exciting field.

01/09/2025 - 01/10/2025

2025 California EIC Consortium Collaboration Meeting

Physics and Astronomy Building, Conference Room 3-326