Bulletin of the American Physical Society
2021 Fall Meeting of the APS Division of Nuclear Physics
Volume 66, Number 8
Monday–Thursday, October 11–14, 2021; Virtual; Eastern Daylight Time
Session DH: Mini-symposium: Hadron Production and Interactions in Jets and Media I |
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Chair: Sevil Salur, Rutgers Room: Whittier |
Tuesday, October 12, 2021 9:30AM - 10:06AM |
DH.00001: Heavy Flavor and Strangeness Production in Jets in the Vacuum and in the Nuclear Medium Invited Speaker: Ivan M Vitev In this talk I will discuss flavor production in lepton-hadron, hadron-hadron, lepton-nucleus, and nucleus-nucleus collisions. Run 3 of the Large Hadron Collider, the continued operation of the Relativistic Heavy Ion Collider, and the rapid progress toward the Electron Ion Collider will provide new and, in many cases, unprecedented opportunities to test Quantum Chromodynamics, understand the physics of hadronization, and advance the many-body physics of hadron and jet production in the nuclear environment. Flavor production, including strangeness, charm, and beauty, can give unique insights into the role of mass in the formation of parton showers, complement our understanding of how energy and matter are transported in strongly-interacting matter, and place constraints on the non-perturbative processes of fragmentation and particle absorption. I will discuss the similarities and differences in the physics of hard probes in the quark-gluon plasmas of the early universe and in cold nuclear matter on using examples of hadron and jet cross sections and jet substructure. |
Tuesday, October 12, 2021 10:06AM - 10:18AM |
DH.00002: An Investigation of Flavor Dependence of Jet Shape Modifications in Au+Au Collisions at $\sqrt{s_{NN}} = 200$ GeV Diptanil Roy Partons (quarks/gluons) generated in large energy transfer processes during a heavy ion collision offer a way to experimentally probe the Quark Gluon Plasma (QGP). Once produced, these partons traverse the QGP medium, before fragmenting into collimated sets of particles called jets. Partons interact strongly with the QGP, and hence have their energy and shower structure modified compared to those in vacuum, e.g., those produced in proton-proton collisions. The differential jet shape, $\rho$, defined as the distribution of fractional momenta in a jet, has been shown to undergo modification in the presence of QGP at LHC energies. Theoretical calculations show that radiative energy loss, which is the dominant mode of energy loss for gluons and light quarks in the QGP, is suppressed for heavy quarks (such as charm and bottom) at low transverse momenta. In this talk, we will present preliminary measurements of $\rho$ for anti-$k_{T}$ jets of radius $R=0.4$, tagged with $D^0 (c\bar{u})$ mesons in Au+Au collisions at $\sqrt{s_{NN}} = 200$ GeV collected by the STAR experiment in 2014, and compare them to PYTHIA-8 predictions. Such measurements are expected to shed light on parton flavor and mass dependencies of jet quenching, and constrain theoretical models. |
Tuesday, October 12, 2021 10:18AM - 10:30AM |
DH.00003: Studying φ(1020) meson in jet and medium production in p-Pb collisions with the ALICE detector at the LHC Justin T Blair Current measurements show an enhancement of strange particles (e.g. an increase in the φ(1020)/π ratio ratio as a function of multiplicity) in p-Pb and high multiplicity pp collisions with respect to minimum bias pp collisions. To probe the origin of this increase, we separate the strange particles produced in hard processes (jets) from those produced in soft processes (bulk) by means of the measurement of two-particle angular correlations. |
Tuesday, October 12, 2021 10:30AM - 10:42AM |
DH.00004: Exploring hadronization and non-perturbative physics via jet substructure Raghav Kunnawalkam Elayavalli Jets are algorithmic proxies of hard scattered quarks/gluons that are created in collisions of high energy particles. The last few years has seen an explosion of jet substructure results derived from exploiting clustering algorithms, both via analysis techniques and experimental data. Such measurements have resulted in the theoretical community extending perturbative calculations to higher orders that are now capable of describing precise substructure data in pp collisions across two orders of magnitude in center of mass energy. Since jets are multi-scale objects, they encode information about both the perturbative (pQCD) parton shower and non-perturbative (npQCD) physics including hadronization. In this talk, to study the pQCD to npQCD transition across various collision systems, we discuss the utility of the formation time which is a substructure observable calculated from splits from the jet clustering tree and simultaneously via charged particles in the final state. We present Monte Carlo studies of the formation time and discuss them in the context of recent work on such observables in heavy ion collisions where they potentially enable a time dependent tomography of the deconfined medium. |
Tuesday, October 12, 2021 10:42AM - 10:54AM |
DH.00005: Lepton-jet correlations with H1 data and machine-learning unfolding Miguel I Arratia Recently, jet measurements in deep-inelastic scattering (DIS) events close to Born kinematics have been proposed as a new probe to study transverse-momentum-dependent (TMD) PDFs, TMD fragmentation functions, and TMD evolution. This channel also has great potential to study cold-nuclear matter effects in electron-nucleus DIS. In this talk, I will report measurements of lepton-jet momentum imbalance in high-Q2 DIS events collected with the H1 detector at HERA. These data bridge DIS measurements from fixed target experiments and Drell-Yan measurements at colliders, thus providing a stringent test of TMD factorization, evolution and universality. This measurement also represents the first example of unfolding assisted with machine learning. These results serve as a pathfinder for the Electron-Ion Collider 3D imaging program. |
Tuesday, October 12, 2021 10:54AM - 11:06AM |
DH.00006: Theory of Jet-Flow Coupling in Nuclear Media Matthew D Sievert, Andrey Sadofyev, Ivan M Vitev Jets have long been envisioned as a source of tomographic information about hot and cold nuclear media, with signatures such as their energy loss, acoplanarities, and substructure encoding information about the microscopic details of the medium. The theory of jet-medium interactions fundamentally relies on a significant separation of scales, referred to as the eikonal approximation, in which the jet energy far exceeds the temperature and other characteristic scales of the nuclear medium. In the strict eikonal limit under which these formulas are derived, the constituents of the medium are effectively static, with corrections sensitive to the motion of medium particles being suppressed by the jet energy. In this talk, we report on a new calculation of these sub-eikonal corrections which are sensitive to the velocity distribution of the medium. We show that these corrections lead to significant qualitative modifications of the usual jet-medium interactions, including collisional energy gain or loss, direction-dependent shifts in the scattering cross section, and new types of quantum interference phases. The result, applicable both to heavy-ion collisions and to cold nuclear matter at the Electron-Ion Collider, is a drift effect which drags the jet in the direction of the velocity field and alters the angular distribution of its radiation pattern. |
Tuesday, October 12, 2021 11:06AM - 11:18AM |
DH.00007: Study of $\Lambda$ SIDIS in the Current and Target Fragmentation Regions using CLAS Taya N Chetry The hadronization or fragmentation process defines the transformation of the energetic struck quark into color-neutral hadrons. The latter is an effective probe of the confinement mechanism that entails all color charge to be asymptotically resolved into color singlet subsystems. Yet, the hadronization study yields a scan of the two characteristic time-scales involved in the process. These time-scales are significant to elucidate our understanding of the color-neutralization and subsequent non-perturbative formation of the observed hadrons. This talk will report the first-ever analysis of the semi-inclusive deep inelastic scattering (SIDIS) of $\Lambda$ hyperon in the current and target fragmentation regions using various CLAS6 5-GeV nuclear targets data-sets. Results on multiplicity ratios and the transverse momentum broadening will be presented. The results from this work along with other CLAS6 meson studies are pioneering the upcoming CLAS12 color propagation measurements. |
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