Open Heavy Flavor Measurement at Forward Angles for Cu+Cu Collisions at Center of Mass NN Collision Energy 200 GeV

Irakli Garishvili, University of Tennessee - Knoxville

Doctoral Dissertation


‎The main purpose of Relativistic Heavy Ion Collider (RHIC) program is to study the Quark-Gluon Plasma (QGP), a deconfined state of matter believed to be created in ultra-relativistic heavy ion collisions. Heavy quarks, expected to be produced during the earlier stages of heavy ion collisions, serve as an important probe of the QGP.‎

‎The following dissertation presents measurements of single muons resulting from the semileptonic decay of heavy flavor quarks in the rapidity range of $1.4 < \vert\eta\vert < 1.9$ for Cu+Cu nuclei collisions at $\sqrt{s_{NN}}=200$ GeV measured by the PHENIX experiment. Single muon spectra were measured for three different centrality classes (0 - 20 \% , 20 - 40 \%, 40 - 94 \%) within the $p_{T}$ range of 1.0 - 4.0 GeV/c.‎

‎To calculate single muon spectra, a full background estimate was statistically subtracted from inclusive spectra of muon candidate tracks reconstructed in the PHENIX muon arms. The background was predicted and estimated with a ``Hadron Cocktail", a full-scale data-driven Monte Carlo simulation. The hadron cocktail approach was originally developed and implemented to measure single muon production for Run-5 p+p collisions. First, the relevant light hadrons are generated with a ``realistic'' input (ratios of different particle species and $p_{T}$ spectra). The generated tracks are then propagated through the PHENIX detector geometry using GEANT. At the last step, introduced and implemented specifically for this analysis, the simulated tracks were embedded into real events and finally reconstructed with the PHENIX muon arms reconstruction software. This was done to realistically reproduce detector performance due to effects caused by colliding heavy ions. The hadron cocktail method provides a much better alternative to the previously attempted purely data-driven peacemeal approaches which suffer from very large systematic uncertainties.‎ ‎Finally, using baseline single muon measurements for p+p collisions, nuclear modification factors for all of the above specified centralities have been measured. These are the first measurements of single muon spectra and nuclear modification factors at forward angles for any two heavy colliding ion systems.