Understanding Heavy Flavor Production At Rhic PDF Download

The research field of this work is experimental nuclear physics. I use data taken with the Solenoidal Tracker At RHIC (STAR) experiment at the Relativistic Heavy Ion Collider (RHIC), an accelerator facility located at Brookhaven National Laboratory (BNL) in Long Island, NY. RHIC accelerates beams of protons, light and heavy ions (e.g. Au nuclei) to relativistic velocities and collides them. The collisions compress and heat the nuclear matter to very high temperatures and densities, over one trillion degrees Celsius. Under such conditions a phase transition might occur in nuclear matter, a transition, where quarks and gluons become de-confined, i.e. free to move around, forming the so-called Quark Gluon Plasma (QGP). The study of the properties of QGP, its properties and dynamics, provide a deeper understanding of Quantum Chromo-Dynamics (QCD), the theory of strong force, and the conditions in the early universe. A key finding by the experiments at RHIC is the unexpected strong suppression of heavy flavor at high transverse momentum values in Au+Au relative to elementary proton-proton collisions. Heavy quarks are mainly produced during the early stages of the collision when the most energetic interactions occur. The suppression of heavy flavor particles is caused by their interaction with the produced medium, as they traverse it. Charm and bottom quark production can be used as a tool to better probe the matter created during the early phases of the collision. The available theoretical models at that time under-predicted the observed suppression. In order to better understand the observed phenomenon and the details of the interaction between heavy flavor quarks and the hot nuclear medium, precision measurements of mesons containing charm or bottom quarks needed to be performed by the experiments. Heavy flavor mesons are unstable particles and most of them decay weakly within the first millimeter from the production vertex. Their relative low production rates, low branching ratios (B.R.) to useful channels and short lifetimes (ctau), e.g. D0 -> K¿ + pi (B.R. = 3.89% and ctau = 123μm) makes their reconstruction a challenging task. One needs a very-high precision vertex detector in order to separate the decay products from the thousands of particles produced in the collision. The STAR collab- oration built such a detector, the Heavy Flavor Tracker (HFT) with state-of-the-art silicon pixel technology. The HFT gives us the track pointing precision required to efficiently reconstruct charm and bottom meson decay vertices from background. The work in this Thesis is concentrated around the track pointing performance of HFT, sometimes called DCA (Distance of Closest Approach). More specifically we studied the HFT performance using data taken during its first physics run, Run14, that took place in 2014. We present and discuss the details of our analysis methods and the obtained results. We demonstrate that the HFT achieved and exceeded its original design goals in terms of track pointing resolution.