Bulletin of the American Physical Society
2007 Joint Spring Meeting of the Texas Sections of APS, AAPT, and SPS
Volume 52, Number 2
Thursday–Saturday, March 22–24, 2007; Abilene, Texas
Session APS3: APS III - Nuclear and High Energy Physics |
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Chair: Rusty Towell, Abilene Christian University Room: Foster Science Building 350 |
Friday, March 23, 2007 3:30PM - 3:42PM |
APS3.00001: Extending the Measurement of the Anti-Quark Flavor Asymmetry of the Nucleon. Rusty Towell Fermilab E866/NuSea performed the first measurements of Drell-yan cross section ratio of p+p to p+d collisions over a large kinematic range, allowing the extraction of the ratio of anti-down to anti-up quarks in the proton. After reviewing E866 results, improvements that can be made on these measurements by taking advantage of the Fermilab Main Injector will be discussed. The lower energy of the Main Injector provides a higher Drell-Yan cross section, allowing the extension of all measurements to higher Bjorken-x. E906 is an approved experiment that plans to make these measurements in the near future. [Preview Abstract] |
Friday, March 23, 2007 3:42PM - 3:54PM |
APS3.00002: Resistive Plate Chambers and the Forward PHENIX Upgrade at RHIC Donald Isenhower The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) is in the process of upgrading the forward region of the detector to allow for a level one trigger to reject low-momentum muons. The goal is to improve the rejection of low $p_T$ particles by a factor of 5,000 to 10,000. This will allow the selection of events with W bosons in high luminosity polarized proton-proton collisions during $\sqrt{s} = 500$ GeV at RHIC, providing a powerful tool to study the spin dependent distributions for quarks and anti-quarks seperately for each quark flavor. The chosen solution consists of three Resistive Plate Chamber (RPC) stations for each muon arms constructed of bakelite designed to handle rates on the order of 1,000 events/cm$^2$. They will cover the forward and backward rapidity ($1.2 < |y| < 2.2$) regions. Prototypes of these chambers will utilize experience of other collaborations building similar RPCs. The major differences required for PHENIX is that they must be able to be installed into the already assembled detector. These and other challenges will require some unique aspects to the PHENIX RPC design. [Preview Abstract] |
Friday, March 23, 2007 3:54PM - 4:06PM |
APS3.00003: ABSTRACT WITHDRAWN |
Friday, March 23, 2007 4:06PM - 4:18PM |
APS3.00004: Minimum-bias correlations in relativistic heavy ion collisions Michael Daugherity An overview of minimum-bias two-particle correlation results from STAR at RHIC is presented emphasizing the unique access this analysis provides to interactions of jets with the dense, colored medium produced in heavy-ion collisions [1]. A general correlation measure is derived from standard statistical definitions and applications to RHIC physics will be discussed. Recent results of correlations on relative azimuth and pseudorapidity at 62 and 200 GeV showing strong energy and centrality dependences will be reported. [1] J. Adams et al. (STAR Collaboration), Phys. Rev. C73 (2006) 064907; J. Adams et al., Phys. Lett. B634 (2006) 347 [Preview Abstract] |
Friday, March 23, 2007 4:18PM - 4:30PM |
APS3.00005: Reducing uncertainty in relativistic heavy ion collision centrality Lanny Ray, Michael Daugherity Uncertainties in heavy ion collision centrality measures relevant to the Relativistic Heavy Ion Collider (RHIC) program are estimated using a Monte Carlo Glauber collision model where particle production is generated via ``soft + hard'' two-component phenomenology [1]. Collision centrality is characterized by the measured multiplicity frequency distribution and in the model by the overlap geometry of two colliding nuclei. The principle sources of uncertainty include those associated with the input parameters to the Monte Carlo model and errors in the experimental minimum-bias multiplicity distributions. The latter include backgrounds plus uncertainties in the trigger and collision vertex finding efficiencies. It is shown that simultaneous analysis of the minimum-bias multiplicity frequency distributions and trigger detector output for both heavy ion and proton-proton collisions using a power-law representation of the data enables the systematic errors in centrality measures to be reduced compared to previous published analyses, thus permitting access to peripheral collision data from RHIC. Simulation results are presented for minimum-bias Au-Au collisions at 200 GeV. ~~~~[1] R. L. Ray and M. Daugherity, nucl-ex/0702039. [Preview Abstract] |
Friday, March 23, 2007 4:30PM - 4:42PM |
APS3.00006: Cosmic Ray Test Setup for STAR Time of Flight Development and Production Quality Assurance Kohei Kajimoto The new Time-of-Flight (TOF) subsystem for STAR at RHIC will have 3840 6-pad Multigap Resistive Plate Chambers (MRPC) distributed over 120 trays. Each tray contains 32 6-pad MRPCs and 3 types of custom made readout electronics boards. A cosmic ray test system is used to test the components of the system and to determine the timing resolution expected to be achieved for the full system. The test system is comprised of three plastic scintillators, 4 MRPC modules, and TOF prototype electronics. An overall resolution of 80-100 ps has been achieved. An overview of the STAR TOF subsystem and a discussion of the test setup/results will be presented. [Preview Abstract] |
Friday, March 23, 2007 4:42PM - 4:54PM |
APS3.00007: Status of the Forward Meson Spectrometer Jim Drachenberg The Forward Meson Spectrometer (FMS) is an upgrade from the Forward Pi0 Detector (FPD) at RHIC's STAR detector. In preparation for RHIC run 7, a 2 meter by 2 meter stack of lead glass detectors was assembled for commissioning during the Au+Au run. The FMS will provide insights into many areas of the RHIC program including investigating single spin asymmetries in transverse polarized proton collisions, gluon polarization, and nuclear gluon densities. This talk will report the status and outlook of the FMS for RHIC run 7. [Preview Abstract] |
Friday, March 23, 2007 4:54PM - 5:06PM |
APS3.00008: Isotopic Temperatures and Chemical Equilibrium in Heavy Ion Collisions Armando Barranon, Jorge Lopez, Claudio Dorso Several Heavy Ions violent Collisions have been simulated using LATINO Model obtaining early signals of chemical and thermodynamical equilibrium at the time when Isotopic Temperature Plateaus are built up. Isotopic Temperature Plateaus are in the range of asymptotic experimental temperatures. This confirms the expectations about early signals of equilibrium for the light particle channels in Heavy Ions violent collisions, as reported by NIMROD Collaboration. [Preview Abstract] |
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