Bulletin of the American Physical Society
2012 Fall Meeting of the APS Division of Nuclear Physics
Volume 57, Number 9
Wednesday–Saturday, October 24–27, 2012; Newport Beach, California
Session KB: Relativistic Heavy Ions: Jets and the Future of Jet Measurements |
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Chair: Jim Thomas, Lawrence Berkeley National Laboratory Room: Garden I |
Friday, October 26, 2012 2:00PM - 2:12PM |
KB.00001: ABSTRACT WITHDRAWN |
Friday, October 26, 2012 2:12PM - 2:24PM |
KB.00002: Jet Shape Analysis for $\sqrt{s_{NN}}=2.76$ TeV Pb+Pb collisions using the ATLAS Detector at LHC Ryan Mandelbaum Observations of strongly modified dijet asymmetry distributions in Pb+Pb collisions at the LHC indicate significant quenching of jets in the hot dense medium created in the collisions. Other measurements suggest that the energy lost by the jets appears in particles at large angles with respect to the jet axis, contrary to expectations based on radiative energy loss calculations. This conclusion can be tested using measurements of jet shapes which provide direct sensitivity to the angular distribution of energy within jets and which can probe the angular distribution of medium-induced radiation. ATLAS has measured jet shapes in Pb+Pb collisions at 2.76~TeV using data collected in 2011 corresponding to an integrated luminosity of approximately 140~$\mu {\rm b}^{-1}$. Jets were reconstructed using the anti-kt algorithm with distance parameters, R = 0.2 and 0.4. Results will be presented for differential jet shapes and distributions of energy as a function of $\Delta \eta$ and $\Delta phi$ with respect to the jet axis. The evolution of the jet shapes with collision centrality will be evaluated. [Preview Abstract] |
Friday, October 26, 2012 2:24PM - 2:36PM |
KB.00003: Measurement of jet quenching in direct photon-jet events in lead-lead collisions at $\sqrt {s_{NN} } =2.76\mbox{ TeV}$ Rafael Krichevsky, Peter Steinberg, Brian Cole Direct photons are an important resource for studying the physics of jet quenching in heavy ion collisions. Recent measurements have shown that jets lose energy when traveling through a dense QCD medium; isolated photons can be used to calibrate the associated jet energy and evaluate the extent of quenching. In this analysis, results will be presented for measurements of photon-jet correlations using approximately $140\mbox{ }\mu b^{-1}$ of data from lead-lead collisions at nucleon center-of-mass energy $\sqrt {s_{NN} } =2.76\mbox{ TeV}$, recorded by the ATLAS detector at the Large Hadron Collider. Events that have isolated prompt photons with transverse momentum $p_T >65\mbox{ GeV}$ opposite jets with $p_T >25\mbox{ GeV}$ are considered, and the transverse momentum imbalance is quantified by means of the ratio $X_{J\gamma } =p_T^{\mbox{jet}} /p_T^\gamma $ for different collision centralities, photon energy bins and angular cuts. Background subtraction, efficiency, unfolding and jet-scale corrections are applied to the measured distributions, which are compared in turn to perturbative QCD calculations. [Preview Abstract] |
Friday, October 26, 2012 2:36PM - 2:48PM |
KB.00004: Measurements of Jets and Jet Properties with the ATLAS Detector Aaron Angerami The energy loss of high-$p_{\mathrm{T}}$ partons through the phenomenon of jet quenching provides insight into the transport properties of the medium created in relativistic heavy ion collisions. Evidence for this energy loss was first experimentally established through observation of high-pt hadron suppression at RHIC. This observable is not ideal for detailed quenching measurements as the final state hadrons are only relatable to the jet through the fragmentation. More recently, measurements of fully reconstructed jets have been performed at the LHC. This talk presents the latest experimental results from the ATLAS collaboration on jets including jet suppression, dijet asymmetry and measurements of jet properties such as the fragmentation function. These results establish qualitative features of the jet quenching mechanism as experimental fact and provide constraints on models of jet energy loss. [Preview Abstract] |
Friday, October 26, 2012 2:48PM - 3:00PM |
KB.00005: sPHENIX Upgrade Program James Nagle The PHENIX collaboration has submitted a proposal for a major upgrade, referred to as sPHENIX, enabling key new physics capabilities for the RHIC facility. A comprehensive program of jets, dijets, and gamma-jet probes of the quark-gluon plasma in a temperature range of strongest coupling are enabled. In addition, future incremental upgrades allow for tagging of heavy flavor jets, multiple upsilon state measurements, and other key observables. We detail the unique and also the complementary physics to the LHC heavy ion program and the detector program that makes it possible. [Preview Abstract] |
Friday, October 26, 2012 3:00PM - 3:12PM |
KB.00006: Jets as a probe of the QGP at RHIC energies David Morrison Jets are an established probe of properties of the QGP created in heavy-ion collisions at the highest energies. With a suitable detector---such as the proposed sPHENIX upgrade--and with effective techniques for subtracting the underlying event and for unfolding the effects of smearing, one can use jet observables as powerful probes of the physics of the QGP in heavy-ion collisions at RHIC energies. Jet observables at RHIC and at the LHC provide the greatest information when seen as a part of a complementary and comprehensive set of measurements. We will discuss methods and techniques which will enable strong jet probe measurements in heavy-ion collisions at RHIC energies and their potential sensitivity to underlying QGP physics. [Preview Abstract] |
Friday, October 26, 2012 3:12PM - 3:24PM |
KB.00007: Upsilon measurements at RHIC with an upgraded sPHENIX detector Anthony Frawley The three Upsilon states provide a powerful probe of color screening in the QGP created in heavy ion collisions at the LHC and at RHIC. With the addition of outer tracking layers and additional electron capability, the proposed sPHENIX detector at RHIC would enable Upsilon measurements at RHIC energies with separation of the three states and statistical precision comparable with that of the LHC experiments. In combination, Upsilon data from the LHC and from sPHENIX at RHIC would show the effects of widely different energy densities and underlying bottom quark production rates on the modification of the three Upsilon states in the QGP. We will discuss the expected performance for Upsilon measurements of the sPHENIX detector with the proposed additional capabilities. [Preview Abstract] |
Friday, October 26, 2012 3:24PM - 3:36PM |
KB.00008: The sPHENIX Detector at RHIC John Haggerty The sPHENIX detector is a proposal to build a superconducting solenoidal spectrometer covering two units of rapidity with excellent electromagnetic and hadronic calorimetry at RHIC. The detector is designed for studying the Quark Gluon Plasma with reconstructed jets, but can serve as a basis for future measurements of upsilon states, neutral pion, direct photon, and photon-jet measurements. The detector design takes advantage of technological advances, a dozen years of PHENIX upgrades and operations, and the flexibility of the RHIC accelerator facility to provide a diverse range of collision species and energies for a premier facility to study hot, dense nuclear matter. [Preview Abstract] |
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