Date of Award

12-17-2015

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Physics and Astronomy

First Advisor

Xiaochun He

Second Advisor

Murad Sarsour

Third Advisor

Raphael Tieulent

Fourth Advisor

Russel White

Abstract

The PHENIX experiment at the Relativistic Heavy Ion Collider (RHIC) has measured ϕ meson production and nuclear modification in asymmetric Cu+Au heavy-ion collisions at 200 GeV at both forward Cu-going direction (1.2 < y < 2.2) and backward Au-going direction (-2.2 < y < -1.2) rapidities. Due to its very short lifetime, the ϕ meson is an excellent probe for studying the hot and dense state of nuclear matter, referred to as the quark-gluon plasma (QGP), that is produced in high-energy heavy-ion collisions, such as those at RHIC. Furthermore, the absence of strong interactions between muons and the surrounding hot hadronic matter makes the ϕ decay channel particularly useful for studying nuclear matter effects on ϕ meson production. Additionally, the rapidity dependence of ϕ meson production in asymmetric heavy-ion collisions provides a unique means of accessing the entanglement of hot and cold nuclear matter effects. However, the large combinatorial background produced at forward and backward rapidities in heavy-ion collisions results in a very challenging environment for extracting the ϕ meson signal. Accordingly, previous measurements at RHIC were limited to smaller collision species, p+p and d+Au. In this paper, a procedure for modeling and removing the backgrounds is detailed, and the first ϕ meson measurement at forward and backward rapidites in heavy-ion collisions at RHIC is presented. The ϕ meson invariant yield and nuclear-modification factor are reported as a function of the number of participating nucleons, rapidity, and transverse momentum in the kinematic region 1.2 < |y| < 2.2 and 1 < pT < 5 GeV/c. Results of this analysis provide insight into the mixture of hot and cold nuclear matter effects on ϕ meson production in asymmetric heavy-ion collisions, bringing scientists one step closer to understanding the QGP.

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