Bulletin of the American Physical Society
APS April Meeting 2021
Volume 66, Number 5
Saturday–Tuesday, April 17–20, 2021; Virtual; Time Zone: Central Daylight Time, USA
Session Y14: Heavy Flavor and Quarkonia as a Probe of QCD Media, Current and Future – IILive
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Sponsoring Units: DNP Chair: Daniel Tapia Takaki, Kansas University |
Tuesday, April 20, 2021 1:30PM - 1:42PM Live |
Y14.00001: Bottomonium suppression and elliptic flow using Heavy Quarkonium Quantum Dynamics Ajaharul Islam, Michael Strickland We introduce a framework called Heavy Quarkonium Quantum Dynamics (HQQD) which can be used to compute the dynamical suppression of heavy quarkonia propagating in the quark-gluon plasma using real-time in-medium quantum evolution. Using HQQD we compute large sets of real-time solutions to the Schr\"{o}dinger equation using a realistic in-medium complex-valued potential. After taking into account final state feed down we compare our results to existing experimental data for the suppression and elliptic flow of bottomonium states and find that HQQD predictions are good agreement with available data for $R_{AA}$ as a function of $N_{\rm part}$ and $p_T$ collected at \mbox{$\sqrt{s_{\rm NN}} =$ 5.02 TeV}. Our prediction for the integrated elliptic flow for $\Upsilon(1s)$ in the $10{-}90$\% centrality class, which includes an estimate on the systematic error, is \mbox{$v_2[\Upsilon(1s)] = 0.0026 \pm 0.0007 \pm\,^{0.0005}_{0.001}$}. We also find that, due to their increased suppression, excited bottomonium states have a larger elliptic flow. Based on this observation we make predictions for $v_2[\Upsilon(2s)]$ and $v_2[\Upsilon(3s)]$ as a function of centrality and transverse momentum. [Preview Abstract] |
Tuesday, April 20, 2021 1:42PM - 1:54PM Live |
Y14.00002: PHENIX Measurement of J/$\psi$ Elliptic Flow in 200 GeV Au+Au Collisions at Forward Rapidity Luis Bichon The Quark Gluon Plasma (QGP) produced in relativistic heavy ion collisions exhibits a nearly perfect fluid behavior, which manifests itself in strong azimuthal correlations between the produced particles. This behavior is seen for both light and heavy-flavor particles, but the detailed interactions of the heavy quarks in the medium are still under investigation. Quarkonia may serve as a special probe, as they are subject to several competing effects that involve interactions of both the bound state and the individual heavy quarks with the QGP. PHENIX has unique coverage at forward rapidity and a large data set of Au+Au collisions at 200 GeV collected in 2014. This will allow for a statistically improved measurement of J/$\psi$ elliptic flow. A the J/$\psi$ flow analysis will be presented. [Preview Abstract] |
Tuesday, April 20, 2021 1:54PM - 2:06PM Live |
Y14.00003: Limits on Intrinsic Charm Production from the SeaQuest Experiment Ramona Vogt A nonperturbative charm production contribution, known as intrinsic charm, has long been speculated but has never been satisfactorily proven. The SeaQuest experiment at FNAL is in an ideal kinematic region to provide evidence of $J/\psi$ production by intrinsic charm. Here, $J/\psi$ production in the SeaQuest kinematics is calculated with a combination of perturbative QCD and intrinsic charm to see whether the SeaQuest data can put limits on an intrinsic charm contribution\footnote{R. Vogt, to be submitted to Phys. Rev. C.}. $J/\psi$ production in perturbative QCD is calculated to next-to-leading order in the cross section. Cold nuclear matter effects included in this component are nuclear modification of the parton densities, absorption by nucleons, and $p_T$ broadening by multiple scattering. The $J/\psi$ contribution from intrinsic charm is calculated assuming production from a $|uudc \overline c \rangle$ Fock state. The nuclear modification factor, $R_{pA}$, is calculated as a function of $x_F$ and $p_T$ for $p+ {\rm C}$, $p+{\rm Fe}$, and $p+{\rm W}$ interactions relative to $p+{\rm d}$. It is shown that the SeaQuest kinematic acceptance is ideal for setting limits on intrinsic charm in the proton. [Preview Abstract] |
Tuesday, April 20, 2021 2:06PM - 2:18PM Live |
Y14.00004: Magneto-Rotational Melting of Quarkonia in Quark Gluon Plasma Kirill Tuchin Quark-Gluon Plasma produced in Relativistic Heavy Ion Collisions is characterized by large vorticity and is subject to intense magnetic field. The Lorentz force exerted by this magnetic field on the moving quarkonium can tear the quarkonium apart by causing its quark or antiquark to tunnel through the potential barrier. The corresponding decay rate, computed using the WKB approximation, strongly depends on plasma vorticity. Moreover, since the Lorentz force depends on electric charge whereas the vorticity does not, the decay rate of positively and negatively charged bound states is different. [Preview Abstract] |
Tuesday, April 20, 2021 2:18PM - 2:30PM Live |
Y14.00005: Measurement of the charge asymmetry in highly boosted top-quark pair production in pp collision data collected by the CMS experiment Hugo Becerril As a consequence of charge asymmetry in relevant processes for heavy flavor production in the LHC, top quarks are produced preferentially in the direction of the incoming quark. This results in more forward top quarks and more central top antiquarks. A central--forward charge asymmetry for the \textit{tt} \textunderscore production, referred to as the charge asymmetry (Ac) can be altered by several BSM processes. In this report, we will discuss an inclusive and differential measurement of the charge asymmetry as function of the invariant mass of \textit{tt} \textunderscore system in highly boosted top-quark pair production using the full Run II CMS data at a center of mass energy of $=$ 13 TeV. To identify jets corresponding to boosted tt \textunderscore events, we use substructure variables compatible with the hadronic decay of the top quark. The employment of two DNNs is used to suppress Standard Model (SM) background processes in two steps, first a QCD killer DNN and a second DNN to separate ttbar from all the other backgrounds. Finally, we will discuss the introduction of regularized unfolding techniques applied to correct bin-by-bin smearing due to finite detector resolution, limited acceptance, and event selection. [Preview Abstract] |
Tuesday, April 20, 2021 2:30PM - 2:42PM Live |
Y14.00006: Measurement of $\gamma\gamma\rightarrow\mu^+\mu^-$ pairs in non-ultra peripheral Pb+Pb collisions with the ATLAS detector Benjamin Gilbert ATLAS measurements of dimuons produced via $\gamma\gamma$ scattering processes in inelastic, non-ultra-peripheral Pb+Pb collisions at 5.02 TeV are presented using an integrated luminosity of 1.9 nb$^{-1}$. The $\gamma\gamma\rightarrow\mu^+\mu^-$ pairs are identified via selections on pair momentum asymmetry and acoplanarity, and the contribution from the heavy flavor decay background is estimated using a template fit method. The pair yields are measured differentially as functions of the centrality, average transverse-momentum ($p_T$) and rapidity of the pair. The measurement shows a depletion in the number of muon pairs near zero acoplanarity in central events, resulting in the distributions peaking at non-zero values of acoplanarity. Fits to the perpendicular transverse momentum ($k_\perp$) distributions are used to estimate the centrality dependence of this peak position. The most probable is shown to increase from the most peripheral to the most central collisions, reaching a value of $k_\perp=36\pm1$ MeV in the 0-5\% most-central collisions. The capacity of these measurements to distinguish between recent theoretical predictions and underlying physical mechanisms for the observed behavior are discussed. [Preview Abstract] |
Tuesday, April 20, 2021 2:42PM - 2:54PM Live |
Y14.00007: PHENIX measurements of elliptic flow of prompt hadrons and inclusive muons at forward rapidity in 200 GeV Au$+$Au collisions Brandon Blankenship h $-abstract-$\backslash $pard Near perfect fluid behavior is a hallmark signature of the quark gluon plasma (QGP), however, how this behavior emerges is still not fully understood. Thus, measurements of many different types of particles over a wide rapidity range are needed to understand this phenomenon. PHENIX has unique capabilities for measuring particles at forward rapidity using the forward silicon vertex detector (FVTX) and muon spectrometers. The flow of heavy flavor particles can be measured via their decay muons using PHENIX's forward rapidity instrumentation. In addition, the FVTX allows for the separation of decay muons from charm and beauty particles respectively. Measuring the flow of hadrons and inclusive muons is a step towards measuring the elliptic flow of charm and beauty quarks at forward rapidity via the muon decays of D and B mesons in 200 GeV Au$+$Au collisions. The status of these ongoing measurements will be presented.$\backslash $pard-/abstract-$\backslash $\tex [Preview Abstract] |
Tuesday, April 20, 2021 2:54PM - 3:06PM Live |
Y14.00008: Photon emission from strongly magnetized QCD plasma Igor Shovkovy, Xinyang Wang, Lang Yu, Mei Huang By making use of an explicit Landau-level representation for the imaginary part of the photon polarization tensor, the direct photon emission from a strongly magnetized quark-gluon plasma is calculated. The leading order contribution comes from the three processes of the zeroth order in the coupling constant $\alpha_s$: (i) the quark splitting ($q\rightarrow q+\gamma $), (ii) the antiquark splitting ($\bar{q} \rightarrow \bar{q}+\gamma $), and (iii) the quark-antiquark annihilation ($q + \bar{q}\rightarrow \gamma$). It is found that the Landau-level quantization leads to a nontrivial momentum dependence of the photon ellipticity coefficient $v_2$, which takes negative values at small transverse momenta and positive values at large transverse momenta. The crossover between the two regimes occurs around $k_T\simeq \sqrt{|eB|}$. The nonisotropic photon emission may explain in part a large positive value of $v_2$ for the direct photons produced in ultrarelativistic heavy-ion collisions. [Preview Abstract] |
Tuesday, April 20, 2021 3:06PM - 3:18PM Live |
Y14.00009: The Emission of Electromagnetic Radiation From the Early Stages of Relativistic Heavy-ion Collisions Jessica Churchill, Li Yan, Sangyong Jeon, Charles Gale A notable achievement of relativistic heavy-ion studies is the realization that relativistic fluid dynamics can describe the evolving system of quark-gluon plasma (QGP) from its early moments to a time when the growing mean-free-paths drive the system out of equilibrium. The effectiveness of this description is judged by comparing calculated observables with experimental measurements. Electromagnetic radiation is considered a distinguishing signal as it is emitted throughout the evolution of the hadronic system. Considerable work has gone into the calculation of photons and dileptons using modern hydrodynamic approaches, however, the calculation of the electromagnetic emissivity of the early stage is currently less advanced. In this talk, we estimate the production of electromagnetic radiation from the early, pre-equilibrium, stage of relativistic heavy-ion collisions using the parton dynamics obtained as a solution of the Boltzmann equation in the Fokker-Planck diffusion limit. The photon and dilepton yield is calculated and compared with available experimental data. The pre-equilibrium electromagnetic contribution can be non-negligible at the current LHC energies, depending on the saturation scale. Predictions are made for Pb+Pb at $\sqrt{s_{\rm NN}} = 5.02$ TeV. [Preview Abstract] |
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