Bulletin of the American Physical Society
APS April Meeting 2014
Volume 59, Number 5
Saturday–Tuesday, April 5–8, 2014; Savannah, Georgia
Session X6: Relativistic Heavy Ions: A+A |
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Sponsoring Units: DNP Chair: Helen Caines, Yale University Room: 200 |
Tuesday, April 8, 2014 10:45AM - 10:57AM |
X6.00001: Measurement of the Total Cross Section of Uranium-Uranium Collisions at $\sqrt{s_{NN}} = 192.8$ GeV A.J. Baltz, W. Fischer, M. Blaskiewicz, D. Gassner, K.A. Drees, Y. Luo, M. Minty, P. Thieberger, M. Wilinski, I.A. Pshenichnov The total cross section of Uranium-Uranium at $\sqrt{s_{NN}} = 192.8$ GeV has been measured to be $515 \pm 13^{stat} \pm22^{sys}$ barn, which agrees with the calculated theoretical value of 487.3 barn within experimental error[1]. That this total cross section is more than an order of magnitude larger than the geometric ion-ion cross section is primarily due to Bound-Free Pair Production (BFPP) and Electro-Magnetic Dissociation (EMD). Nearly all beam losses were due to geometric, BFPP and EMD collisions. This allowed the determination of the total cross section from the measured beam loss rates and luminosity. The beam loss rate is calculated from a time-dependent measurement of the total beam intensity. The luminosity is measured via the detection of neutron pairs in time-coincidence in the Zero Degree Calorimeters. Apart from a general interest in verifying the calculations experimentally, an accurate prediction of the losses created in the heavy ion collisions is of practical interest for the LHC, where collision products have the potential to quench cryogenically cooled magnets.\\[4pt] [1] W. Fischer, A.J. Baltz, M. Blaskiewicz, D. Gassner, K.A. Drees, Y. Luo, M. Minty, P. Thieberger, M. Wilinski, and I.A. Pshenichnov, arXiv:1401.0213v1 [nucl-ex]. [Preview Abstract] |
Tuesday, April 8, 2014 10:57AM - 11:09AM |
X6.00002: Forward physics at PHENIX with precision silicon tracking J. Matthew Durham The PHENIX experiment at RHIC has developed and installed a new silicon detector, the Forward Silicon Vertex Tracker (FVTX), to provide precise tracking at forward and backward rapidity ($1.2<\vert y\vert <2.2)$. The FVTX consists of four layers of silicon mini-strip sensors with a 75 micron pitch in the radial direction, and is located in front of the existing PHENIX muon arms. By determining muon tracks with high precision before any interactions occur in the hadron absorber, the FVTX will enhance the mass resolution of dimuon resonance measurements as well as allow separation of decay muons from charm and bottom hadrons produced in heavy ion collisions. In this talk, the design and capabilities of the FVTX will be discussed, along with the analysis status of FVTX data. [Preview Abstract] |
Tuesday, April 8, 2014 11:09AM - 11:21AM |
X6.00003: Heavy flavor single muon flow measurement in Cu$+$Au collisions from PHENIX Brandon Schmoll Asymmetric collisions of heavy nuclei, such as Cu$+$Au, provide unique initial geometry configurations unlike those found in symmetric nucleus-nucleus collisions. This offers us an opportunity to study the Quark-Gluon Plasma under different initial conditions. In central collisions the Cu nucleus will be completely embedded in the Au nucleus. Single muon measurements at forward rapidity allow us to quantify the effect of this embedding by studying, for example, flow in the Cu-going versus the Au-going directions. The status of the current analysis and the challenges that arise from trying to measure heavy flavor single muons will be discussed. [Preview Abstract] |
Tuesday, April 8, 2014 11:21AM - 11:33AM |
X6.00004: J/psi Measurements in Cu+Au and U+U Collisions from PHENIX Abhisek Sen The measurement of quarkonia production in relativistic heavy ion collisions provides a powerful tool for studying the properties of the hot and dense matter created in these collisions. PHENIX's ability to measure J/psi in a wide kinematic range and RHIC's flexibility to collide different nuclei provide a unique opportunity for such measurements in order to systematically test various quarkonia suppression models. In the 2012 run, RHIC has collided Cu+Au and U+U nuclei. These collisions promise an array of unique initial geometrical configurations which present an opportunity to measure J/psi production in a wide range of initial energy densities. Recent J/psi results from Cu+Au and U+U data from PHENIX will be discussed. [Preview Abstract] |
Tuesday, April 8, 2014 11:33AM - 11:45AM |
X6.00005: Two jet production at large x as a probe of superfast quarks in nuclei Adam Freese, Misak Sargsian, Mark Strikman We have developed a theoretical framework for the calculation of two jet production in p-A scattering at LHC energies which allows us to probe a nuclear partonic distributions at moderate to large Bjorken x. Due to the large invariant momentum transfer involved in the reaction, the QCD evolution of partonic distributions is sensitive to the nuclear quarks with very large initial momentum fractions. Based on the few-nucleon short range correlation model of the nuclear wave function, we estimated the cross section of the reaction and the sensitivity of the measured process to a possible transition from hadronic to quark-gluon degrees of freedom in the nucleus. [Preview Abstract] |
Tuesday, April 8, 2014 11:45AM - 11:57AM |
X6.00006: Jet studies in Pb-Pb collisions with ALICE at LHC Joel Mazer High energy heavy ion collisions allow the study of nuclear matter at high temperatures and energy densities, where a Quark Gluon Plasma (QGP) is formed. One way of probing the QGP is by measuring the resulting energy loss from the suppression of jets. A jet is the collimated shower of hadrons produced by a parton resulting from a hard scattering early in the collision. In heavy ion collisions, partons undergo interactions with the QGP, which reduces the jet energy. In non-central collisions, the asymmetry of the hot and dense matter profile is expected to lead to a dependence of the jet yield on the angle with respect to the reaction plane. The current methods used in ALICE for studies of full jets will be discussed. Full jets are reconstructed from clusters using the Electromagnetic Calorimeter (EMCal) detector and charged tracks from the ALICE tracking system. The current status of studies of jets in Pb-Pb collisions relative to the reaction plane will be presented. [Preview Abstract] |
Tuesday, April 8, 2014 11:57AM - 12:09PM |
X6.00007: Measurement of pion, kaon, and proton spectra in U+U collision at $\sqrt{s_{NN}}$ = 193 GeV with PHENIX Brennan Schaefer The Relativistic Heavy Ion Collider at Brookhaven National Lab allows nuclear matter to be studied at extremely high temperatures and energy densities. RHIC is uniquely versatile in it's ability to collide a wide range of species. In 2012 RHIC saw the first ever high energy collisions with the irregularly shaped uranium nuclei, providing the possibility to produce systems with different initial energy density profiles for the same number of participating nucleons. This allows for systematic investigation of the effects of initial geometry and density on particle production. The work in progress for measurement of the identified pion, kaon, and proton spectra as a function of centrality will be presented. The nuclear modification factor ($R_{AA}$) and particle ratios such as kaon/pion, proton/pion, and antiproton/proton will also be studied and compared with the ratios measured in Au+Au collisions. [Preview Abstract] |
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