Bulletin of the American Physical Society
2008 Annual Meeting of the Division of Nuclear Physics
Volume 53, Number 12
Thursday–Sunday, October 23–26, 2008; Oakland, California
Session CF: Experimental Methods at RHIC and the LHC |
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Chair: Flemming Videbaek, Brookhaven National Laboratory Room: Simmons Ballroom 4 |
Friday, October 24, 2008 10:30AM - 10:42AM |
CF.00001: High-density QCD with CMS at the LHC Haidong Liu We will present the capabilities of the Compact Muon Solenoid (CMS) experiment to explore the rich heavy-ion physics programme offered by the CERN Large Hadron Collider (LHC). The collisions of lead nuclei at energies $\sqrt{s_{_{NN}}}$ = 5.5 TeV will probe quark and gluon matter at unprecedented values of energy density. The prime goal of this research is to study the fundamental theory of the strong interaction --- Quantum Chromodynamics (QCD) --- in extreme conditions of temperature, density and parton momentum fraction (low-$x$). This presentation will cover in detail the potential of CMS to carry out a series of representative Pb-Pb measurements. These include ``bulk'' observables --- charged hadron multiplicity, low $p_{\rm T}$ inclusive hadron identified spectra and elliptic flow --- which provide information on the collective properties of the system; as well as perturbative processes --- such as quarkonia, heavy-quarks, jets, $\gamma$-jet, and high $p_{\rm T} $ hadrons --- which yield ``tomographic'' information on the hottest and densest phases of the reaction. [Preview Abstract] |
Friday, October 24, 2008 10:42AM - 10:54AM |
CF.00002: ATLAS Jet Reconstruction Capabilities in Heavy Ion Collisions Aaron Angerami High pT jets provide a unique tool for understanding the medium induced energy loss of the ~nuclear matter created in heavy ion collisions. ~The large acceptance of the ATLAS detector as well as recent advances in jet reconstruction algorithms have created a prime opportunity for jet physics in heavy ion collisions at the LHC. ~In this talk I will present results on the performance of the ATLAS jet reconstruction in Pb-Pb collisions. ~I will summarize a systematic program of treating the large background present in this collisions as well as the capabilities of different algorithms. [Preview Abstract] |
Friday, October 24, 2008 10:54AM - 11:06AM |
CF.00003: PHENIX Silicon Vertex Detector (VTX) Upgrade Performance Capabilities Richard Petti A silicon vertex detector upgrade is being developed for use in the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC) located at Brookhaven National Lab (BNL). This detector features four layers to enable charged particle tracking near the collision vertex. The inner two layers (sitting at radius of 2.5cm and 5.0cm from the beam line) are constructed of pixel sensors, where as the outer two layers (at 10cm and 14cm) are of a novel stripixel design. This upgrade will significantly improve the collision vertex resolution of PHENIX. This allows us to detect off-vertex decays and to separate charm and bottom decays by the DCA (Distance of Closest Approach) resolution. The DCA is calculated by first identifying electron tracks in the PHENIX central arms and projecting the track back to track candidates in the VTX. Then the matching VTX track can be traced back towards the collision vertex and the point at which the distance between the collision vertex and the helical track is smallest can be found. Results on charm/bottom separation from a full Monte Carlo simulation will be presented. [Preview Abstract] |
Friday, October 24, 2008 11:06AM - 11:18AM |
CF.00004: Testing of the PHENIX Silicon Pixel Detector at Fermi National Laboratory Nicole Apadula The Silicon Vertex Tracker (VTX) is a new upgrade to PHENIX at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory (BNL). The VTX is composed of two layers of a silicon pixel detector and two layers of a silicon stripixel detector. The innermost layers, at 2.5cm and 5cm from the beam line, consist of silicon pixel sensors capable of reconstructing tracks and achieving good DCA (Distance of Closest Approach) resolution. The DCA is the smallest distance between the collision vertex found by the VTX and the track reconstructed from the PHENIX central arms. Good DCA resolution will allow a clean identification of charm and bottom decays. This is accomplished with a 50 x 425 $\mu$m$^{2}$ cell size and low material budget to avoid multiple scattering. Three layers of the Silicon Pixel Detector will be placed in a test beam at Fermi National Laboratory (FNAL) to check tracking capabilities and efficiencies. The results will be presented. [Preview Abstract] |
Friday, October 24, 2008 11:18AM - 11:30AM |
CF.00005: Zero bias and HF-based minimum bias triggering for pp collisions at 14 TeV in CMS Jeremy Callner The start of LHC running and the corresponding initial low luminosities during ramp-up to full luminosity represent a unique, and possible one time, opportunity to obtain a significant amount of usable minimum bias pp data without the added complications and potential biases associated with data containing multiple collisions per bunch crossing. Important considerations need to be taken into account in the design of the trigger system to enable the effective recording of relevant minimum bias events. A description of two possible triggering schemes for minimum bias collisions will be presented. One based on a zero bias crossing-time trigger for specific luminosity situations and the second, a detector trigger based on HF, the forward calorimeters in CMS. Possible biases imposed on the data at the triggering level and ways to reject (or accept) beam gas collisions will also be discussed. [Preview Abstract] |
Friday, October 24, 2008 11:30AM - 11:42AM |
CF.00006: The STAR Forward GEM Tracker Jan Balewski The STAR collaboration is preparing a tracking detector upgrade, the Heavy Flavor Tracker (HFT) [1] and the Forward GEM Tracker (FGT) to further investigate fundamental properties of the new state of strongly interacting matter produced in relativistic-heavy ion collisions at RHIC and to provide fundamental studies of the proton spin structure and dynamics in high-energy polarized proton-proton collisions at RHIC. The FGT will focus on novel spin physics measurements in high-energy polarized proton-proton collisions, determining the flavor dependence ($\Delta \bar{u}$ versus $\Delta \bar{d}$) of the polarized sea. STAR plans to probe these PDFs using parity violating W production and decay. $W^{-(+)}$ bosons are produced in $\bar{u}+d\,(\bar{d}+u)$ collisions and can be detected through their leptonic decays, $e^{-}+\bar{\nu}_{e}\,(e^{+}+\nu_{e})$, where only the respective charged lepton is measured. The sensitivity of those measurements is enhanced in the forward direction. The discrimination of $\bar{u}+d (\bar{d}+u)$ quark combinations requires distinguishing between high $p_{T}$ $e^{-(+)}$ through their opposite charge sign. An upgrade of the STAR forward tracking system is needed to provide the required tracking precision for charge sign discrimination. This upgrade will consist of six triple-GEM detectors with two dimensional readout arranged in disks along the beam axis. The FGT design and installation schedule will be presented. [1] The STAR Heavy-Flavor Tracker, DNP Fall 2008 Meeting. [Preview Abstract] |
Friday, October 24, 2008 11:42AM - 11:54AM |
CF.00007: A Very High Momentum Particle Identification Detector for Alice Edmundo Garcia The anomalies observed at RHIC for the baryon - meson ratios have prompted a number of theoretical works on the nature of the the hadronisation stage of the pp collisions and in the evolution of the dense system formed in heavy ion collisions. Although the predictions differ in the theoretical approach, generally a substantial increase in the baryon production is predicted in the range 10-30 GeV/c. This raises the problem of baryon identification to much higher momenta than originally planned in the LHC experiments. After a review of the present status of theoretical predictions we will present the possibilities of a gas ring imaging Cherenkov detector of limited acceptance. The physics capabilities of such a detector in conjunction with the ALICE experiment will be contemplated as well as the triggering options to enrich the sample of interesting events with a dedicated trigger or/and using the ALICE Electromagnetic Calorimeter. The use of the electromagnetic calorimeter opens interesting possibility to distinguish quark and gluon jets in gamma - jet events and subsequently the study of the probability of fragmentation in proton, kaon and pion or triggering on jets in the EMCAL. Such a detector would be identify pions until 14 GeV/c kaons from 9 till 14 GeV/c and protons from 18 till 24 GeV/c in a positive way. Additionally identification of protons by absence of signal is possible from 9-18 GeV/c. [Preview Abstract] |
Friday, October 24, 2008 11:54AM - 12:06PM |
CF.00008: Nose-Cone Calorimeter: upgrade of PHENIX detector Ondrej Chvala PHENIX experiment at RHIC is efficient at measuring processes involving rare probes, but has limited acceptance in azimuth and pseudorapidity ($\eta$). The Nose Cone Calorimeter (NCC), a W-Si sampling calorimeter in the region of 0.9\,$<\eta<$\,3, is one of the upgrades which will dramatically increase coverage in azimuth and pseudorapidity. The NCC will expand PHENIX's precision measurements of electromagnetic probes in $\eta$, reconstruct jets, and enhance triggering capabilities. It will significantly contribute to measurements of $\gamma$-jets, quarkonia, and low-$x$ nuclear structure functions. Details of the detector design, performance, and a sample of the physics topics which will benefit from the NCC, will be discussed. [Preview Abstract] |
Friday, October 24, 2008 12:06PM - 12:18PM |
CF.00009: Measurements of Direct Photon Double Longitudinal Spin Asymmetry at Large Rapidity Paul Bourgeois Direct photon production in polarized p-p collisions is expected to be the cleanest measurement of the gluon polarization. Current measurements using inclusive pion production, in the PHENIX central arms, suggest a small contribution from the gluons to the proton spin in the presently accessible Bjorken $x$ range $x_{Bj}>10^{-2}$. The addition of the Nose Cone Calorimeter (NCC) in the large rapidity $1<\eta<3$ will allow PHENIX to access $x_{Bj}\sim 10^{-3}$. In this talk I will present the prospects of measuring direct photon double longitudinal spin asymmetry $A_{LL}$ employing the NCC. [Preview Abstract] |
Friday, October 24, 2008 12:18PM - 12:30PM |
CF.00010: Performance and Monitering of Zero Degree Calorimeter at CMS Heidi LeSage The CMS Zero Degree Calorimeter is designed to measure photons and neutrons for pp and PbPb collisions at TeV energies. The detector can be used for physics and for measuring the brightness and luminosity of the beams. This poster will show the performance of the calorimeter in test beams and describe the monitoring systems we have developed to ensure that the calorimeter is working correctly. [Preview Abstract] |
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