A Study Of J Psi Production In 260 Gev Pi Negative Nucleus Collisions

Author : Darren McGlinchey
Publisher :
ISBN 13 :
Total Pages : pages
Book Rating : 4.:/5 (859 download)

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Download or read book Cold Nuclear Matter Effects on J/psi-->e+e- and Psi'-->;e+e- Production in D+Au Collisions at 200 Gev written by Darren McGlinchey and published by . This book was released on 2012 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: ABSTRACT: Mesons composed of heavy quark-antiquark pairs, known as quarkonia, provide the only direct probe of the screening length in the deconfined state of quarks and gluons, known as the quark gluon plasma (QGP), which is believed to be produced in high energy heavy ion collisions. However, the observation of suppression of quarkonia production in heavy ion collisions at high energies is complicated by the modification of quarkonia production in normal nuclear matter. Measuring the modification of quarkonia production due to the effects of normal nuclear matter, often termed cold nuclear matter (CNM) effects, provide a critical baseline for understanding the properties of the QGP. Measurements of CNM effects on quarkonia production are also interesting in their own right, and can be measured independently in proton-nucleus (p+A) collisions. The modification of quarkonia production in p+A collisions provides insight into quarkonia production mechanisms unavailable through the study of proton-proton collisions alone. The study of quarkonia production in p+A collisions over a wide range of kinematic variables can also provide constraints on the modification of parton distribution functions in nuclei. In order to quantify the CNM effects present at the Relativistic Heavy Ion Collider (RHIC), the PHENIX experiment has recorded data on d+Au collisions at \sqsn=200 GeV. The analysis of J/psi→e+e- and psi'→e+e- production from that data set is presented here. Both J/psi and psi' production are found to be suppressed in d+Au relative to p+p collisions, with the suppression increasing for collisions with small impact parameters. The psi' production is found to be much more suppressed than J/psi production, a result which is unexpected based on measurements at lower collision energy and present theoretical pictures. A parametrization of the J/psi modification measured by PHENIX in terms of two CNM effects is also presented. One is the nuclear breakup of the forming quarkonium state through collisions with nucleons during the d+Au collision. The other is the modification of the gluon distribution in the Au nucleus. It is found that the two effects can be separated due to the very different impact parameter dependencies. A strongly non-linear geometric dependence on the modification of the gluon distribution function is observed, with the modification found to be concentrated near the center of the Au nucleus. This parametrization is also used to estimate the modification of J/psi production in Au+Au collisions due to CNM effects. This modification is compared to PHENIX measurements of J/psi production in Au+Au collisions. Suppression of J/psi production in Au+Au collisions beyond CNM effects is observed. This excess suppression is interpreted as suppression of J/psi production due to the formation of a QGP.