Bulletin of the American Physical Society
2020 Fall Meeting of the APS Division of Nuclear Physics
Volume 65, Number 12
Thursday–Sunday, October 29–November 1 2020; Time Zone: Central Time, USA
Session DB: Heavy Ions and Jets I |
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Chair: Rongrong Ma, Brookhaven National Laboratory |
Friday, October 30, 2020 8:30AM - 8:42AM |
DB.00001: Probing multi-scale dynamical interactions between heavy quarks and the QGP using JETSCAPE Gojko Vujanovic The shower development for a jet traveling through the QGP involves a variety of scales, e.g. the mass for heavy quarks. Though the mass of these quarks plays a sub-dominant role during the high virtuality portion of the jet, it affects the longitudinal drag and diffusion, stimulating additional radiation, which is modeled using the MATTER generator inside the JETSCAPE framework. These emissions partially compensate the reduction in radiation from the dead cone effect. In the lower virtuality (nearly on-shell) part of the shower, scattering and radiation processes off heavy and light quarks differ and are described by the LBT generator in JETSCAPE. Throughout this study, event by event modeling is used for shower development and for fluid dynamical medium simulations. Energy-momentum exchange with the medium proceeds using a weak coupling recoil approach. The transition scale between MATTER and LBT happens on the level of individual partons, and can be extracted from a comparison with data; i.e. leading hadron $R_{AA}$ and $v_2$. This allows to explore the effects/interplay between the different regimes of energy loss on the propagation and radiation from heavy quarks in a dense medium. [Preview Abstract] |
Friday, October 30, 2020 8:42AM - 8:54AM |
DB.00002: D$^{0}$-tagged jets in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with ALICE at the LHC Antonio Carlos Oliveira da Silva Heavy quarks, due to their large masses, are produced in the early stages of high-energy hadronic collisions in hard-scattering processes. Therefore, they are ideal probes of the quark-gluon plasma (QGP). The mass-dependent energy loss in the QGP is investigated using jets tagged by D$^{0}$ mesons. The modification of the yields as a function of jet transverse momentum in Pb--Pb collisions in comparison with pp collisions provides information on the charm-quark interaction with the medium. In this contribution the measurement of D$^{0}$-tagged jets in Pb--Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV with the ALICE detector will be presented. The presence of the charmed meson as a jet constituent enhances the rejection of jet combinatorial background allowing the study of the jet spectrum down to low $p_{\mathrm{T}}$, where probes are more sensitive to hot nuclear matter effects. [Preview Abstract] |
Friday, October 30, 2020 8:54AM - 9:06AM |
DB.00003: Heavy jet evolution in QGP using the JETSCAPE framework Wenkai Fan, Gojko Vujanovic The dynamics of shower development for a jet traveling through the quark-gluon plasma (QGP) involves a variety of scales, including the mass for heavy flavors in jets. Though the mass of the heavy quarks plays a subdominant role during the high virtuality portion of the jet, it does affect longitudinal drag and diffusion, stimulating additional radiation from heavy quarks. These emissions partially compensate the reduction in radiation from the dead cone effect. In the lower virtuality part of the shower, when the mass is comparable to the transverse momentum of the parton, scattering and radiation processes off heavy quarks are different than off light quarks. All these factors result in a different shower development for heavy-flavor tagged jets. The QGP evolution is modeled on an event by event basis using the JETSCAPE Framework. We present a multi-stage calculation that explores the importance of differences between various heavy quark energy-loss mechanisms within a realistically expanding medium. Energy-momentum exchange with the medium, essential for the study of jet modification, proceeds using a weak coupling recoil approach. Heavy jets as well as their substructure, give us a handle to study the heavy quark shower development. [Preview Abstract] |
Friday, October 30, 2020 9:06AM - 9:18AM |
DB.00004: Modification of Jet Properties in Central Relativistic Heavy-ion Collisions in a Transport Model Weiyao Ke, Xin-Nian Wang In relativistic heavy-ion collisions, hot QCD medium effects modify jets relative to those produced in proton proton collisions. Interaction between medium and constituents of jets takes place from the hard process scale down to the soft medium scale, providing rich information on the dynamics of hard processes in a hot nuclear environment. In this work, we used a transport model approach to understand the modifications of jet properties in heavy-ion collisions and addressed the origin of these modifications to physical ingredients implemented in the transport model. In particular, we studied the inclusive jet nuclear modification factor $R_{AA}$ at RHIC and LHC, modification to jet fragmentation function $D(z)$, and jet shape $\rho(r)$, focusing on the central region of heavy-ion collisions. We found the redistribution of jet constituents at large $r$ and small $z$ are sensitive to the jet-induced medium excitation and elastic collisions, while medium-induced radiative processes are important to understand suppression of high-$p_T$ particles. Finally, we discuss how the combinations of these observables help to determine the applicable regime of a perturbative partonic transport approach and map out the transport parameters of partons at different energy scales. [Preview Abstract] |
Friday, October 30, 2020 9:18AM - 9:30AM |
DB.00005: Constraints on jet quenching from multi-stage energy-loss approach Amit Kumar A unified description of the jet evolution through deconfined QCD matter remains as one of the challenging problems in the area of heavy-ion physics. In this talk, we demonstrate a successful description of leading hadron and jet observables using a multi-stage energy loss approach. Within the framework of JETSCAPE [1,2], an effective parton evolution is set up which includes a high-virtuality radiation dominant region, followed by a low-virtuality scattering dominant phase. Measurements of inclusive jet and single-hadron $R_{AA}$ set strong constraints on the phase-space available for each stage of the energy-loss. The jet-medium response is incorporated through a weakly-coupled transport description with recoil particles excited from the QGP. We also study the cone size dependence of the nuclear modification factor for jets. This serves as an excellent probe to study the detailed mechanism of the lost jet energy inside the plasma. [1] JETSCAPE Collaboration (J. H. Putschke (Wayne State U.) et al.), The JETSCAPE framework, arXiv:1903.07706 [nucl-th] (2019). [2] JETSCAPE Collaboration (S. Cao (Wayne State U.) et al.), Multistage Monte-Carlo simulation of jet modification in a static medium, Phys. Rev. C96 (2017) no.2, 024909. [Preview Abstract] |
Friday, October 30, 2020 9:30AM - 9:42AM |
DB.00006: Jet Quenching in Relativistic Heavy-Ion Collisions Fabio Canedo, Leonardo Campos, Marcelo Munhoz, Jacquelyn Noronha-Hostler, Jorge Noronha In this work jets were simulated on top of either event-by-event 0+1 or 2+1 relativistic hydrodynamic backgrounds using JEWEL+vUSPhydro with two different initial conditions: TRENTo and MC-KLN. The effects of hydrodynamics and initial state on the shape and substructure observables (such as mass, $p_T^D$ and girth) and on jet $v_n$ are presented. No distinguishable impact on shape and substructure observables was seen whereas the comparison between jet $v_n$ calculations and experimental data is significantly improved by the insertion of a realistic hydrodynamic background. [Preview Abstract] |
Friday, October 30, 2020 9:42AM - 9:54AM |
DB.00007: Probing the system-size dependence of parton energy loss in heavy-ion collisions with the STAR detector Audrey Francisco High transverse momentum partons are produced in hard-scattering processes during the initial stages of high energy nucleus-nucleus collisions and lose energy as they interact with the hot dense medium via collisional and radiative processes. Partonic energy loss can be investigated through the study of high transverse momentum particles and jets. While previous measurements have investigated its dependence with the collision energy, we present results that target the sensitivity of parton energy loss to the collision system size. In 2018 STAR recorded a large dataset of the isobars (3.1B events for each species), Ru+Ru and Zr+Zr collisions, at $\sqrt{s_{\rm NN}} = 200$ GeV. This dataset provides a unique opportunity to further explore how the properties of the QGP are affected by the number of participating nucleons and the nucleus shape versus the medium's initial energy density. We explore traditional jet quenching observables in these collision systems where accumulated statistics will allow to investigate parton energy loss in details and compare to similar measurements in Au+Au collisions. [Preview Abstract] |
Friday, October 30, 2020 9:54AM - 10:06AM |
DB.00008: Study of in-medium modification of dijets in PbPb collisions at 5.02 TeV Jussi Viinikainen Jet quenching is one of the well-established signatures of the quark-gluon plasma produced in heavy ion collisions. Studies of energy balance for back-to-back hard probes, as well as medium-induced modifications to jet shapes and fragmentation functions, provide important experimental constraints for theoretical understanding of QGP properties. Using large sample of dijet events from 5.02 TeV PbPb and pp collisions recorded by CMS, we study quenching effects differentially with respect to dijet momentum balance. We use jet-charged particle correlations to assess medium-induced modifications to jet substructures on each side of the dijet, and correlate the observed effects with medium response to dijet propagation. [Preview Abstract] |
Friday, October 30, 2020 10:06AM - 10:18AM |
DB.00009: Jet-medium interaction at non-zero net baryon density Lipei Du, Ulrich Heinz Jet-medium interaction in heavy-ion collisions is a multi-scale problem involving weakly coupled hard processes, such as jet production, and soft, strongly-coupled processes, including the thermalization and fluidization of the energy-momentum exchanged between the jet constituents and the QGP medium. Medium response, which appears as enhanced soft particle production around the jet axis in the final state, is important to interpret observables such as radius dependence of jet suppression and jet shape. Unlike previous studies, in this work we explore jet-medium interaction at non-zero net baryon density, where holographic models predict that jet energy loss $\hat e$ and transverse momentum broadening $\hat q$ show interesting features near the phase transition. We study the propagation of the energy and momentum deposited by jets into a medium with non-zero chemical potential, produced at different beam energies. By looking at the contribution from jet-medium interactions to both charged particle spectra and net proton production we demonstrate the importance of considering chemical potential dependent $\hat e(T,\mu)$ and $\hat q(T,\mu)$ and gain insights into additional constraints on QGP properties from studying jet-medium interactions at low collision energies. [Preview Abstract] |
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