Bulletin of the American Physical Society
4th Joint Meeting of the APS Division of Nuclear Physics and the Physical Society of Japan
Volume 59, Number 10
Tuesday–Saturday, October 7–11, 2014; Waikoloa, Hawaii
Session CJ: Mini-Symposium on Jets and High pT Probes in Heavy Ion Collisions |
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Chair: Anne Sickles, University of Illinois at Urbana-Champaign. Room: Queen's 5 |
Wednesday, October 8, 2014 7:00PM - 7:30PM |
CJ.00001: The temperature dependence of jet transport coefficients Invited Speaker: Abhijit Majumder We review the theory of pQCD based jet energy loss in dense matter. In particular, we will focus on the leading transport coefficients that cause the modification of hard jets and how they arise in the various perturbative schemes. This will be followed by a review of the recent work by the JET collaboration which carried out the first phenomenological extraction of the temperature dependence of the leading coefficient $\hat{q}$. We conclude with discussions on the theoretical calculations and expectations for the temperature dependence of $\hat{q}$ and their significance. [Preview Abstract] |
Wednesday, October 8, 2014 7:30PM - 7:45PM |
CJ.00002: Particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at 2.76 TeV with ALICE Minwoo Kim The one of the main goals of the research in heavy-ion collisions is to study the properties of a deconfined quarks and gluons, Quark-Gluon Plasma(QGP). Due to the gluon radiation and the multiple scattering inside hot and dense medium, propagating partons lose their energy and it causes interesting phenomenon called jet quenching. However it is a challenge to reconstruct full jets including low $p_{T}$ because of background fluctuations from underlying events like elliptic flow. At this point, the powerful method, two-particle correlation provides convenient way to understand the medium effect on the jet fragmentation without full reconstruction of jets. We present the particle-yield modification in jet-like azimuthal di-hadron correlations in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 2.76 TeV with ALICE. By subtracting long-range correlation with $\Delta\eta$ gap condition, we could distinguish jet-like particles from large backgrounds coming from collective effects. The near-side peak shapes have been studied for various $p_{T}$ bins of triggered and associated particles. Extracted parmeters from the fits allows to understand the properties of near-side peaks. The ratio of the yields, $I_{AA}$ and $I_{CP}$ with respect to $p_{T}$ of associated particles are also measured. [Preview Abstract] |
Wednesday, October 8, 2014 7:45PM - 8:00PM |
CJ.00003: Jet Tomography and Opaqueness Evolution from RHIC to LHC Jinfeng Liao High energy jets, penetrating the hot QCD matter created in heavy ion collisions, provide unique probe of the medium property. It is of great interest to extract possible nontrivial temperature dependence of the jet-medium coupling. Particularly sensitive to such T-dependence are two sets of observables: 1) the anisotropy of jet energy loss via the azimuthal angle dependence of suppression $R_{AA}(\phi)$ (or the various harmonic coefficients $v_n$ at high $p_t$); 2) the evolution of the overall suppression with beam energy $R_{AA}(\sqrt{s})$. We report our systematic study of these observables using event-by-event simulations, in comparison with available data from RHIC to LHC. The results strongly suggest a nontrivial enhancement of jet-medium coupling near the parton/hadron phase boundary. Recently emerging evidences for such a scenario from various other jet modelings, as well as efforts to understand such peculiar medium property from microscopic theories will also be discussed. Finally we briefly discuss potential final state jet attenuation in (possibly created) hot medium in the ``mini-bang'' (pPb and dAu collisions) and demonstrate that jet quenching anisotropy could provide a clean probe to tell whether there is substantial final state interaction in those collisions. [Preview Abstract] |
Wednesday, October 8, 2014 8:00PM - 8:15PM |
CJ.00004: Dielectrons from Charm and Bottom meson decays in p-Pb collisions at $\sqrt{s_{\rm NN}}$ = 5.02 TeV measured with the ALICE detector ShinIchi Hayashi Electron-positron pairs (dielectrons) are excellent probes for studying the properties of the medium created in high energy heavy-ion collisions. In the intermediate mass region, above 1 GeV/$c^{2}$, dielectrons from semi-leptonic decays of open heavy flavors are the main contributions to the spectrum. Initial state effects such as gluon shadowing, gluon saturation, and initial state energy loss are very important for heavy quark production. The initial state effects can be investigated by studying proton-nucleus collisions, and the modifications of the transverse momentum and invariant mass spectra of dielectrons with respect to pp give important information on such cold nuclear matter effects in the intermediate mass regions.To access to the intermediate and high mass regions, abundant high $p_{T}$ electron samples are needed. In the ALICE experiment, the Transition Radiation Detector (TRD) is used for the electron identification above $p > 1$ GeV/$c$ momentum. The TRD also provides an electron trigger to enrich the data samples for the study of charmonium and open heavy flavor production. We will present the status of the dielectron analysis in p-Pb collisions at $\sqrt{s_{\rm NN}}$=5.02 TeV. [Preview Abstract] |
Wednesday, October 8, 2014 8:15PM - 8:30PM |
CJ.00005: Direct photon-hadron correlations in Au+Au collisions at $\sqrt{s_{NN}}$ = 200 GeV Measured with PHENIX Huijun Ge High momentum direct photons are produced back-to-back with partons in the initial hard scatterings in heavy ion collisions. Since such photons do not interact strongly with the quark-gluon plasma created in these collisions, their measured momentum will approximately balance that of the opposing parton prior to any medium modification. Therefore, using high-momentum direct photons as triggers and comparing the away-side yields in direct photon-hadron correlations in Au+Au collisions to those in p+p can potentially shed light on how the opposing jet is modified by the medium. This allows us to gain more insight into the parton energy loss mechanisms. In this talk we will present the current progress in analyzing direct photon-hadron correlations in Au+Au collisions at $\sqrt{s_{NN}}$=200 GeV with the data taken in 2011 using the PHENIX detector at RHIC. [Preview Abstract] |
Wednesday, October 8, 2014 8:30PM - 8:45PM |
CJ.00006: ABSTRACT WITHDRAWN |
Wednesday, October 8, 2014 8:45PM - 9:00PM |
CJ.00007: Measurement of charm and bottom quarks medium modification in $\sqrt{s_{NN}}$=200 GeV Cu+Au collisions at RHIC Cesar Da Silva The PHENIX detector at RHIC collected a large sample of Cu+Au collisions at $\sqrt{s_{NN}}$=200 GeV using a new Forward Vertex Detector (FVTX) which covers the rapidity range $1.2 < |y| < 2.2$. With FVTX we can statistically separate charm and bottom quark yields by measuring the displaced vertex of muons. The measurement is done in the Cu going ($1.2 < y < 2.2$) and Au going ($-2.2 < y < -1.2$) directions. The rapidity dependence of the heavy quark yields can reveal if initial state effects measured in p+A collisions factorize with quark-gluon plasma effects in A+A. FVTX can also cover a relatively small transverse momentum of heavy quark made mesons, where the mass of the heavy quarks really matters to distinguish the scenario of the parton energy loss in the hot and dense medium expected to be formed in heavy ion collisions. This talk will detail the physics case and the status of the analysis. [Preview Abstract] |
Wednesday, October 8, 2014 9:00PM - 9:15PM |
CJ.00008: Jet physics with the proposed sPHENIX detector Ali Hanks High energy partons, best studied through full jet reconstruction, are important probes for developing a deeper understanding of the quark-gluon plasma (QGP) produced in heavy ion collisions. The PHENIX collaboration has proposed a series of major upgrades designed to expand our jet reconstruction capabilities and make full use of the enhanced luminosity available at RHIC. The first stage of this plan involves replacing the existing PHENIX central arms with full $2\pi$ electromagnetic calorimetry and adding hadronic calorimetry, enabling a wide range of important jet probe measurements which will complement corresponding measurements at the LHC. Combined with flexible accelerator capabilities able to provide a wide range of collision systems and beam energies, these new capabilities will enable detailed investigation of the properties of the QGP close to $T_c$ where the effective coupling is the strongest. [Preview Abstract] |
Wednesday, October 8, 2014 9:15PM - 9:30PM |
CJ.00009: J/psi and psi' Production at Forward Rapidity in p$+$p and Cu$+$Au Collisions Melynda Brooks J/psi and psi' production are considered to be sensitive to cold nuclear matter effects in nuclei and to the deconfined medium of the Quark Gluon Plasma through color screening effects. With the addition of a Forward Silicon Vertex Detector (FVTX), which was installed in 2012, the PHENIX detector can now clearly separate J/psi and psi' production at forward rapidity using the PHENIX Muon Arms in conjunction with the FVTX. We report on the status of measuring the J/psi:psi' ratios from the Run 13 510 GeV p$+$p and Run 12 200 GeV Cu$+$Au data sets collected by PHENIX. [Preview Abstract] |
Wednesday, October 8, 2014 9:30PM - 9:45PM |
CJ.00010: Exploring forward physics with the PHENIX MPC-EX upgrade Norbert Novitzky The MPC-EX detector is a Si-W preshower extension to the existing Muon Piston Calorimeter (MPC) at PHENIX. Located at forward rapidity, $3.1 < |\eta| < 3.8$, the MPC-EX consists of eight layers of alternating W absorber and Si minipad sensors. Covering a large range at forward rapidity makes the MPC-EX and MPC ideal to access low-x partons in the A nucleus of p+A collisions. The neutral pion and direct photon are excellent probes to separate between the initial and final state effects of the pA collisions. Isolating the direct photon signal requires the MPC-EX to be able to distinguish single showers from double showers. The single versus double shower separation was tested with an electron beam at the SLAC test beam facility. Results from the test beam data will be presented in this talk. [Preview Abstract] |
Wednesday, October 8, 2014 9:45PM - 10:00PM |
CJ.00011: Shower shape analysis with a Silicon-Tungsten pre-shower detector Nicole Apadula A limitation of electromagnetic calorimeters is the position resolution due to the finite size of a shower. In order to improve the position resolution, a Si/W preshower detector was developed as an extension to the existing PHENIX Muon Piston Calorimeter (MPC) at pseudorapidity 3.1-3.8. The MPC-EX uses a dual sensitivity readout card developed to allow sensitivity to MIPs while still capturing the EM shower. The MIP response of the detector was tested with a cosmic ray setup. The MIP peak was found to be 50 channels over pedestal in the high sensitivity channels and consistent from module to module. Electromagnetic showers were measured with a dedicated electron beam at the SLAC test beam facility. The profile (width) and energy were studied as a function of depth. Results from the SLAC test beam will be presented in addition to the cosmic ray test data. [Preview Abstract] |
Wednesday, October 8, 2014 10:00PM - 10:15PM |
CJ.00012: RHICf -- Measurements of very forward particles at RHIC Kiyoshi Tanida In this presentation, we will introduce a newly proposed experiment at Relativistic Heavy Ion Collider (RHIC), named as RHICf (RHIC-forward). The proposal is to install a high-resolution electromagnetic calorimeter in front of a zero-degree hadron calorimeter (ZDC) at the PHENIX interaction point, and to measure cross sections and single spin asymmetries of very forward ($\eta > 6$) neutral particles in proton-proton collision at $\sqrt{s}=510$ GeV. Such information helps to understand the production mechanism, which is beyond purturbative QCD. In addition, together with measurements at LHC, these data are invaluable for calibrating ultra-high energy cosmic ray measurements. [Preview Abstract] |
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