12/12/2024

Collinear Limit of Energy-Energy Correlators in pp and pA Collisions

Xoan Mayo Lopez, University of Santiago de Compostela
11:00 AM Thursday, Knudsen 5-142

Energy-energy correlators (EECs), which measure energy deposition in two detectors as a function of their angular separation, have proven to be a successful observable in vacuum physics, offering direct access to QCD anomalous dimensions. Recently, significant progress has been made in understanding how EECs are modified by the presence of a color medium, with the ultimate goal of using EECs to probe QCD matter properties. In this talk, Xoan will present a non-perturbative model describing EECs across the entire angular range of current experiments, effectively capturing both perturbative and non-perturbative contributions. This model achieves excellent agreement with ALICE and CMS experimental data for pp collisions. Furthermore, nuclear medium modifications are incorporated to describe pA collisions, reproducing trends observed in recent ALICE measurements.

12/03/2024

Resistive Dissipative Magnetohydrodynamics

Khwahish Kushwah, Universidade Federal Fluminense
2:00 PM Tuesday, Knudsen 5-142

Intense magnetic fields are expected to be generated during the initial stages of heavy-ion collisions, reaching peaks of around $10^{19}$ gauss (RHIC) and $10^{20}$ gauss (LHC). These magnetic fields might play a crucial role in influencing the dynamics of the Quark-Gluon Plasma formed in these collisions, which can be studied using the framework of Relativistic Magnetohydrodynamics (RMHD). In this presentation, I will talk about a system consisting of a two-component fluid in the presence of strong magnetic fields. I will discuss the derivation of RMHD equations from the Boltzmann equation, using the method of moments and 14-moment approximation, focusing on the shear stress tensor. These equations are distinct from traditional hydrodynamics, as they show oscillatory dynamics in a linear regime. Additionally, I will touch upon the application of RMHD in the context of Bjorken flow and discuss its broader relevance.

10/29/2024

Recent and Planned Electron-Nucleus Experiments at JLab

Miguel Arratia, UC Riverside
11:00 AM Tuesday, Knudsen 5-142

I will describe recent experiments at Jefferson Laboratory using the CLAS12 detector, an 11 GeV electron beam, and a range of nuclear targets, from deuterium to lead. I will also discuss an upcoming experiment with polarized lithium-7, designed to explore the spin structure of bound protons. The presentation will cover planned measurements of inclusive deep-inelastic scattering, as well as semi-inclusive single and double hadron production. In addition, I will present recent results obtained from 5 GeV data.

10/28/2024

Navigating the Maze of Regge Physics with EFT

Anjie Gao, MIT
10:00 AM Monday, Knudsen 5-142

The high energy (Regge) limit provides a playground for understanding all order loop structures of scattering amplitudes, and plays an important role in the description of many phenomenologically relevant applications, including small-x physics, diffraction, saturation, etc. For the simplest 2->2 Regge amplitude, while well understood in the planar limit, the structure of non-planar corrections introduces many fascinating complexities, for which a general all-order organizing principle is still lacking. In this talk, I discuss the structure of multi-Reggeon exchanges in the context of the effective field theory for forward scattering (Glauber SCET, a top-down EFT derived from QCD), and their factorization into collinear functions and soft functions. I show that the Regge limit can be understood through the rapidity RG evolution of these functions, from which we can define Regge-like anomalous dimensions in a gauge invariant manner. A new feature of the EFT is the ability to calculate these anomalous dimensions from either the soft or collinear sectors. I discuss the solutions of these RG evolutions for different color channels, e.g. 8a (gluon Reggeization), 8s, pomeron, 27, odderon, and 10. Indeed, this EFT organization provides a natural all-order definition of the gluon Regge trajectory for the first time. Along the way, we will see the emergence of a 2-dimensional Regge theory on the transverse plane.

10/10/2024

Imaging the Building Blocks of the Universe

John Terry, Los Alamos National Laboratory
11:00 AM Thursday, Knudsen 5-142

Nuclei account for nearly all visible matter in the universe, yet understanding their internal structure-and how it connects to fundamental particles like quarks and gluons-remains one of the greatest challenges in nuclear physics. The non-perturbative nature of Quantum Chromodynamics (QCD), which governs the strong force, makes mapping the partonic structure of protons and nuclei particularly complex. However, recent advances in effective field theories have provided new tools to explore how nuclei differ from free protons and neutrons. In this talk, I will discuss how imaging nuclear matter is a core focus of the U.S. nuclear physics program, and showcase recent breakthroughs that are bringing us closer to fully mapping these intricate structures. The future of this effort, especially with the Electron-Ion Collider, promises to unlock deeper insights into the fundamental building blocks of our universe.

10/01/2024

Dark photon and dark matter in the MUonE experiment

Isaac Ruoquan Wang, Fermilab
11:00 AM Tuesday, Knudsen 5-142

Dark photon has been a long time proposed new particle. In particular, it could be regarded as a "mediator" between SM and dark sector. Typically dark photon produces displaced vertex signature in experiments. We show that the new proposed, SM-motivated MUonE experiment, is capable of probing dark photon with displaced vertex signature, and is sensitive to the long-existing unprobed "gap" in the dark photon parameter space. Specifically, with the inelastic dark matter model, MUonE can be sensitive to the parameter space that is compatible with correct dark matter abundance. We hope these results can motivate BSM searches on SM-motivated experiments.

09/18/2024

Quantum Anomalies in (Generalized) Parton Distributions

Shohini Bhattacharya, Los Alamos National Laboratory
12:00 PM Wednesday, Knudsen 5-142

In this presentation, we will explore the calculation of perturbative corrections for Deeply Virtual Compton Scattering (DVCS) within a unique kinematic domain, specifically where t >> Λ_QCD²​, with t representing the change in nucleon momentum following scattering. Within this unconventional domain, our calculation reveals a previously undisclosed connection between Generalized Parton Distributions (GPDs) - which describe the three-dimensional structure of nucleons—and quantum anomalies, such as the chiral and trace anomalies of QCD. Notably, anomalies emerge as infrared singularities when t approaches zero. We then validate factorization up to one-loop order by systematically incorporating these singularity-related anomalies into the GPD framework. This development not only broadens the scope of GPD research to include quantum anomalies but also opens new avenues for exploring their implications in both high-energy exclusive processes and lattice QCD studies.

08/12/2024

Loops and quark masses in the dipole picture of DIS

Tuomas Lappi, University of Jyvaskyla, Finland
10:30 AM Monday, Knudsen 5-142

Deep inelastic scattering in the small x gluon saturation regime is often described in the dipole picture. Here one factorizes the virtual photon scattering off a hadronic target into a light cone wave function describing the partonic degrees of freedom of the photon, and the eikonal scattering of these partons off the color field of the target. This talk will report on the recent calculation [1] of the light cone wave functions for a longitudinal [2] or transverse [3] virtual photon to split into partonic states, including for the first time quark masses at one loop accuracy. Using these wave functions we derive, for the first time, the total NLO dipole picture DIS cross sections for longitudinal and transverse virtual photons with quark masses. The calculation has required solving a longstanding issue concerning quark mass renormalization in light cone perturbation theory. The quark masses are renormalized in the pole mass scheme, satisfying constraints from the requirement of Lorentz invariance of the quark Dirac and Pauli form factors.

[1] G. Beuf, T. Lappi and R. Paatelainen, Phys.Rev.Lett. 129 (2022) 7, 072001, [2112.03158 [hep-ph]]
[2] G. Beuf, T. Lappi and R. Paatelainen, Phys.Rev.D 104 (2021) 5, 056032, [2103.14549 [hep-ph]]
[3] G. Beuf, T. Lappi and R. Paatelainen, Phys.Rev.D 106 (2022) 3, 034013, [2204.02486 [hep-ph]]

05/29/2024

Jet EEC in hot QCD

Joao Barata, Brookhaven National Laboratory
12:00 PM Wednesday, Knudsen 5-142

The determination of energy correlators inside jets has seen a recent revival, both in the theory and experimental communities. In the context of Heavy Ion collisions, these observables can give new and complementary information regarding the evolution of jets inside the quark gluon plasma. Nonetheless, our understanding of these observables and the full span of their applicability is still in its infancy, and several open questions remain to be fully understood. In this talk, I will discuss some recent developments in the calculation of two point energy correlators (EECs) in the medium. I will first describe some of the challenges one faces when describing these objects, and show that the magnitude of the medium modifications are heavily dominated by modelling aspects, still not under full control from the theory side. I will then discuss some recent generalizations of EECs, which can be connected to other standard jet substructure tools or allow access to directionality effects.

05/10/2024

Jet tomography of Quark-Gluon Plasma

Xin-Nian Wang, Lawrence Berkeley National Laboratory
12:00 PM Friday, Knudsen 5-142

In this presentation, I will provide a comprehensive summary of our latest research on jet tomography of the quark-gluon plasma. This includes topics such as jet-induced medium excitation and response, the 3D structure of diffusion wake, asymmetric jet shape, and deep learning-assisted jet tomography.

05/08/2024

Quantum simulation of hadronization and quasi-parton distributions in 2d QED

Kazuki Ikeda, Stony Brook University
12:00 PM Wednesday, Knudsen 5-142

In this presentation, I'll explore a sophisticated avenue of quantum simulation focusing on the two-dimensional QED, known as the massive Schwinger model. This model serves as a valuable platform for testing four-dimensional QCD and advancing efficient quantum computation due to its shared properties with QCD, such as confinement, symmetry breaking, and chiral anomaly. I'll delve into a compelling direction of quantum simulation for the Schwinger model, drawing insights from recent fruitful collaborations [1-3]. My presentation will consist of two parts. In the first part, I will address the quasi-parton distributions of the lightest eta-prime meson in the Schwinger model [1]. We found that the first excited state transitions between anomalous and non-anomalous states with coupling strength, showing a cusp at the critical point. The boosted state follows relativistic kinematics but deviates significantly at high speeds. Spatial quasi-parton distributions are computed numerically and compared to light front results. In the second part of my talk, I will explain the real-time evolution of the Schwinger model with time-dependent external source, which allows us to mimic the production of quark jets [2,3]. We explored the nature of eigenstates, finding they initially resemble fermionic Fock states before transitioning into meson-like bound states over time, illustrating real-time hadronization. Eventually, local observables at mid-rapidity stabilize, indicating nearing equilibrium and thermalization.

References:
[1] S. Grieninger, K. Ikeda, I. Zahed, “Quasi-parton distributions in massive QED2: Towards quantum computation”, arXiv:2404.05112 (2024)
[2] A. Florio, D. Frenklakh, K. Ikeda, D. Kharzeev, V. Korepin, S. Shi, K. Yu, “Real-Time Nonperturbative Dynamics of Jet Production in Schwinger Model: Quantum Entanglement and Vacuum Modification”, Physical Review Letters 131 (2), 021902 (2023)
[3] A. Florio, D. Frenklakh, K. Ikeda, D. Kharzeev, V. Korepin, S. Shi, K. Yu, “Quantum simulation of entanglement and hadronization in jet production: lessons from the massive Schwinger model”, arXiv:2404.00087 (2024)

05/03/2024

Pushing Rare Event Search to the Limit with Machine Learning Algorithms

Aobo Li, UC San Diego
12:00 PM Friday, Knudsen 5-142

Rare event searches allow us to search for new physics inaccessible with other means by leveraging specialized radiation detectors. Machine learning provides a new tool to maximize the information provided by these detectors. The information is sparse, which forces these algorithms to start from the lowest level data and design customized models to produce results. The focus of this seminar will be on two main areas within rare event search experiments: neutrinoless double beta decay and dark matter. We will delve into the sophisticated mechanisms of radiation detectors that are specifically designed to detect these extraordinarily rare events. Moreover, the seminar will shed light on the development and application of specialized machine learning algorithms, integrating domain knowledge from fields such as spatiotemporal analysis, geometric deep learning, and time series analysis. In the latter part of the presentation, we will discuss the potential of next-generation AI/ML tools that are being developed to fully realize the discovery capabilities of rare event search experiments.

05/01/2024

Topological Cumulants and Finite Volume Thermodynamics in a Uniform Magnetic Field - Perspectives from Chiral Perturbation Theory

Prabal Adhikari, St. Olaf College
12:00 PM Wednesday, Knudsen 5-142

In this talk, I will discuss recent developments on the impact of magnetic fields on the lowest topological cumulants using chiral perturbation theory, an effective theory of Quantum Chromodynamics that provides model-independent results at weak magnetic fields. In particular, I will discuss sum rules that connect the topological susceptibility and fourth cumulant to the chiral condensate and susceptibilities. Lattice QCD is an important tool to investigate these cumulants, not to mention the chiral condensate, the QCD phase diagram and thermodynamic observables. However, lattice QCD results are contaminated by finite volume corrections, which can be characterized using chiral perturbation theory since it encodes the long-range behavior of QCD. In the latter part of the talk, I will discuss recent developments on the nature of finite volume effects in background magnetic fields and (possibly) Euclidean electric fields.

04/19/2024

Scattering and gluon emission of quark jet in a SU(3) colored field

Meijian Li, Santiago de Compostela U.
12:00 PM Friday, Knudsen 5-142

We developed a numerical method to nonperturbatively study scattering and gluon emission of quark jet traversing a SU(3) colored background field using the light-front Hamiltonian approach [arXiv: 2002.09757, 2107.02225, and 2305.12490]. In this approach, the Hamiltonian is directly derived from the QCD Lagrangian, and the quark wavefunction is expressed as a superposition of different possible states in the phase space throughout the evolution, enabling a quantum and real-time simulation on the amplitude level. We first applied the framework to the quark-nucleus scattering in the |q> Fock space; there, we recovered the eikonal cross-section and revealed a sub-eikonal effect through the transverse coordinate distribution of the quark. We then extended the Fock space to |q>+|qg>, enabling gluon emission and absorption. We extracted various physical quantities with the obtained wavefunction, including transverse momentum broadening and gluon emission rate. In a recent investigation, we study the scenario where the quark originates from far outside the background field and is described as the QCD eigenstate in the |q>+|qg> Fock space.

04/12/2024

Simulating physics with quantum computing

Wenyang Qian, Santiago de Compostela U.
12:00 PM Friday, Knudsen 5-142

Quantum computing has demonstrated the potential to revolutionize our understanding and computational methods in various areas of nuclear physics, heavy-ion physics, and formal quantum field theory. In this talk, I will highlight our recent works using quantum simulation to study quantum field theory, heavy quark thermalization, and in-medium jet evolution. Firstly, we delve into the presentations of quantum fields via qubits and show quantum algorithms to efficiently evaluate thermal properties at finite temperatures for generic quantum field theories. These results will serve as thermal fixed points for upcoming real-time quantum evolution. Secondly, the heavy quark thermalization in the quark-gluon plasma can be well described by a stochastic process with drag terms and diffusion terms. By introducing an accelerated quantum circuit Monte-Carlo framework to simulate heavy quark thermalization, we calculate physical observables with quadratically fewer resources, a boost over the classical simulation. Lastly, the light-front Hamiltonian formalism provides a natural platform to study time evolution problems that are suited to digital quantum computers. By tracking the evolution of a multi-particle jet probe in the presence of a stochastic color field with quantum circuits, we study momentum broadening, gluon production, and entropy growth of the quark jet, which grows polynomially with Fock particles and could be further applied to study particle production.

02/21/2024

Jet substructure and transverse energy-energy correlator

Yiyu Zhou, South China Normal University / UCLA
2:00 PM Wednesday, Hybrid (Knudsen Hall 5-142 and online ZOOM)

I will provide a comprehensive summary of our latest research on jet substructure and the transverse energy-energy correlator.