Bulletin of the American Physical Society
APS April Meeting 2019
Volume 64, Number 3
Saturday–Tuesday, April 13–16, 2019; Denver, Colorado
Session L15: Mini-Symposium on Hard Probes in Heavy Ion Collisions IIFocus
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Sponsoring Units: DNP Chair: J Matthew Durham, Los Alamos National Laboratory Room: Sheraton Plaza Court 4 |
Sunday, April 14, 2019 3:30PM - 4:06PM |
L15.00001: Heavy-Flavor Probes of Hot QCD Matter Invited Speaker: Ralf F Rapp The heavy charm and bottom quarks, and their bound states, are versatile probes of the hot medium created in high-energy heavy-ion collisions. At low momentum, open heavy-flavor particles serve as "Brownian Markers" which allow to extract a fundamental transport parameter of the medium, the heavy-flavor diffusion coefficient. At intermediate momenta, heavy quarks give unique insights into the transition regime from elastic to radiative interactions, as well as into the nature of hadronization. Furthermore, the in-medium spectroscopy of heavy quarkonia, as inferred from transport theoretical approaches, allows to constrain the in-medium QCD force. We emphasize the need for a common theoretical framework to simultaneously treat the open and hidden heavy-flavor sectors, and discuss how such a framework can unravel microscopic mechanisms that drive the properties of the strongly coupled quark-gluon plasma and its hadronization. |
Sunday, April 14, 2019 4:06PM - 4:18PM |
L15.00002: $\phi$(1020) meson production with respect to high momentum hadrons in p-Pb collisions with ALICE at the LHC Justin T Blair Recent measurements show an enhancement of strange particles (e.g. an increase in the $\phi$(1020)/$\pi$ ratio) in p-Pb and high multiplicity p-p collisions. In order to probe the origin of this increase, it is necessary to separate the strange particles produced in hard processes (jets) from those produced in soft processes (bulk). By examining this trend from low to high multiplicity p-Pb collisions, we are able to study the onset of this enhancement from small to large collision systems. |
Sunday, April 14, 2019 4:18PM - 4:30PM |
L15.00003: Measurements of D± and D*± production in Au+Au collisions at √sNN = 200 GeV from STAR Xinyue Ju Charm quarks, owing to their large mass, are predominantly created through initial hard scatterings in relativistic heavy-ion collisions and thus are ideal probes to study the properties of Quark-Gluon Plasma (QGP) produced in these collisions. Thanks to high-precision vertex reconstruction provided by the Heavy Flavor Tracker detector, STAR experiment has been able to perform comprehensive measurements of D0 meson production. The results indicate that charm quarks lose energy and gain significant collectivity when traversing through the QGP medium. Measurements of D± and D*± production are complementary to D0 in studying the charm quark interaction with the medium. Also, potential hot medium effects can shorten the lifetime of D*± and can lead to a modification of the measured D*±/D0 yield ratio in heavy-ion collisions, compared to that in p+p collisions. In this presentation, we report measurements of the production of D± and D*± mesons in Au+Au collisions at √sNN = 200 GeV. The invariant yields are measured at mid-rapidity as a function of transverse momentum pT in different centralities. The nuclear modification factors of D± and the yield ratios of D*±/D0 and D±/D0 as a function of pT and collision centrality are also presented and their physics implications are discussed. |
Sunday, April 14, 2019 4:30PM - 4:42PM |
L15.00004: Recent physics results from the PHENIX experiment with the silicon-vertex detectors Ajeeta Khatiwada The PHENIX experiment at RHIC has studied heavy flavor production through the semi-leptonic and J/ψ decay channels using silicon-vertex detectors covering particles going to central and forward rapidities. These detectors provide precise measurement of the event vertex as well as displacement of the decay muon trajectories from the reconstructed event vertex. This talk will discuss the latest results including charm and bottom yields in p+p collisions at √sNN=200 GeV, their nuclear modifications in Au+Au collisions, azimuthal anisotropies as well as how these studies contribute to our understanding of initial state effects and energy loss mechanism for heavy quarks in the quark-gluon plasma at RHIC. |
Sunday, April 14, 2019 4:42PM - 4:54PM |
L15.00005: Λc and B+ production in Au+Au collision at √sNN= 200 GeV at sPHENIX Yuanjing Ji Recent results from RHIC and LHC show that nuclear modification factor and elliptic flow of open charm hadrons are similar to those of light flavor hadrons. Furthermore, a strong enhancement of Λc/D0 ratio compared to the fragmentation baseline is observed in Au+Au collisions, and in p+p/Pb collisions. Measurements of bottom decay daughters at low pT indicate they are less suppressed when compared with light and charm hadrons. Precision measurements of charm baryon and open bottom production over a broad momentum range are needed for detail understanding of parton energy loss mechanisms and to characterize QGP transport properties. sPHENIX is a planned next generation high-rate jet, Upsilon and open heavy-flavor detector at RHIC. A state-of-the-art MAPS-based silicon detector (MVTX) is proposed to greatly enhance heavy flavor detection capabilities. In this talk, we will present simulation studies of Λc baryon and open bottom hadron measurements in Au+Au collisions at √sNN = 200 GeV utilizing full sPHENIX tracking capabilities with MVTX. The simulation method for estimating expected signal and background will be discussed. Statistical projections of open bottom nuclear modification factor and elliptic flow as well as the Λc/D0 ratio, will be presented. |
Sunday, April 14, 2019 4:54PM - 5:06PM |
L15.00006: Feasibility of Tagging Heavy Flavor Jets at RHIC With Machine Learning George Halal The properties of the Quark-Gluon Plasma (QGP), a hot and dense medium made up of deconfined quarks and gluons (partons), can be studied through ultrarelativistic heavy-ion collisions. In the early stages of the collisions, high energy partons are created, which fragment into sprays of hadrons, called jets. Jets are used to probe the entire evolution of the QGP that they traverse. Classifying jets based on the flavor of the parton that initiated them as heavy or light is a fundamental tool for studying the properties of the QGP as different flavors undergo different levels of collisional and radiative energy losses. It has been shown that it is possible to classify (tag) them at LHC energies (√s = 7 TeV). However, the ratio of production cross sections of light to heavy flavor jets at RHIC energies (√s = 200 GeV) is very high. Therefore, we have developed an artificial neural network that maintains the efficiency while minimizing the misidentification probability of tagging heavy flavor jets at RHIC. We have also developed a new jet tagging strategy, where we only consider jets with at least one high transverse momentum lepton constituent. This selection lowers the ratio of light to heavy flavor jets, increasing the efficiency of tagging heavy flavor jets. |
Sunday, April 14, 2019 5:06PM - 5:18PM |
L15.00007: Baked Alaska: the Fate of Heavy Quark Bound States inside Quark-gluon Plasma Xiaojun Yao, Berndt Mueller, Thomas C Mehen, Steffen A Bass Heavy quarkonium production in heavy ion collisions has been used as an important probe of the quark-gluon plasma (QGP). Due to the plasma screening effect, the color attraction is significantly suppressed at high temperature and thus bound states “melt”. However, experiments have shown many quarkonia survived the hot QGP. It is realized that the in-medium recombination of unbound heavy quark pairs is as crucial as the quarkonium melting and dissociation. Thus, phenomenological studies have to account static screening, dissociation and recombination consistently. Transport equations and the open quantum system formalism have been used. In this talk, I will present a connection between them. I will discuss insights about the quarkonium dynamics inside QGP from the perspective of quantum information. I will show that under the weak coupling and Markovian approximations, the Lindblad equation turns to a Boltzmann transport equation after a Wigner transform. I will demonstrate how the separation of physical scales justifies the approximations, by using effective field theory of QCD. Finally, I will show some phenomenological results based on the derived transport equation.
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