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Measurement of Direct Photons in Ultra-Relativistic Au+Au Collisions

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dc.contributor.advisor Drees, Axel en_US
dc.contributor.advisor McCarthy, Robert en_US
dc.contributor.author Gong, Haijiang en_US
dc.contributor.other Department of Physics en_US
dc.date.accessioned 2017-09-20T16:51:01Z
dc.date.available 2017-09-20T16:51:01Z
dc.date.issued 2014-12-01 en_US
dc.identifier.uri http://hdl.handle.net/11401/76701 en_US
dc.description 145 pgs en_US
dc.description.abstract Direct photons provide a tool to study the different stages of a heavy ion collision, especially the formation of the quark-gluon-plasma (QGP), without being influenced by the strong reaction and hadronization processes. The yield of direct photons can be determined from the inclusive photon yield and the photon yield from hadronic decays. At low p<sub>T</sub>, where a significant fraction of direct photon is expected to come from the thermalized medium of deconfined quarks and gluons and interacting hadrons, the measurement is very challenging. These so-called thermal photons carry information about the initial temperature of the medium. We present a new analysis technique that was developed to improve direct photon production measurement in the low and medium p<sub>T</sub> range. The technique was applied to the PHENIX Run4 Au+Au sqrt(s<sub>NN</sub>)=200GeV/c collisions dataset. It uses strict particle identification (PID) in the Electromagnetic Calorimeter (EMCal) and a charged particle veto to extract a clean photon signal. These photons are then tagged with EMCal photon candidates with loose PID cuts, which can be reconstructed with high efficiency, to determine the fraction of photons originating from neutral pion decays. Most systematic uncertainties and detector effects cancel in this method. The results are compared with recent PHENIX direct photon measurement through external conversion method and theoretical calculation predicting thermal photon production. en_US
dc.description.sponsorship This work is sponsored by the Stony Brook University Graduate School in compliance with the requirements for completion of degree. en_US
dc.format Monograph en_US
dc.format.medium Electronic Resource en_US
dc.language.iso en_US en_US
dc.publisher The Graduate School, Stony Brook University: Stony Brook, NY. en_US
dc.subject.lcsh Physics en_US
dc.subject.other Direct Photon, Gold Collisions, PHENIX, Photon, RHIC, Thermal Photon en_US
dc.title Measurement of Direct Photons in Ultra-Relativistic Au+Au Collisions en_US
dc.type Dissertation en_US
dc.mimetype Application/PDF en_US
dc.contributor.committeemember Kuo, Thomas en_US
dc.contributor.committeemember David, Gabor en_US

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