On Kinetic Transport in Small System Collectivity and a Measurement of Separated Open Heavy Flavor Production in p+p Collisions at \Sqrt{s}=200 Gev

The present dissertation consists of two distinct parts. The first one is a comprehensive study of collective behavior in small collision systems from the point of view of kinetic theory, in which the medium formed in heavy-ion collisions is modeled as a collection of interacting quasiparticles. We investigate how parton scattering, where individual partons undergo very few scatters, can translate the initial collision geometry to final-state azimuthal anisotropy, yielding results in agreement with experimental data in a variety of systems, from 3He+Au to p+p collisions, and over a wide range of collision energies, prompting the question of the minimal conditions for collective behavior to appear within this framework. The second part consists of an experimental measurement of the charm and bottom decay electron cross section in p+p collisions at &radic;(sNN) = 200 GeV using the PHENIX detector at the Relativistic Heavy Ion Collider. Unlike previous measurements of inclusive heavy flavor electrons, we present a measurement of each flavor separately. The measurement proceeds by identifying a candidate sample of electron tracks, constructing a simulated electron cocktail to isolate the electron candidates from heavy flavor decays, and using a Bayesian inference procedure to statistically determine the provenance of electrons based on precise displaced vertex measurements. The resulting electron cross sections are consistent with perturbative QCD calculations, exhibiting small uncertainties and large kinematic reach, making them valuable baseline measurements for the future study of in-medium heavy flavor modification in other collision systems, such as A+A and p+A.</p

Heavy quark flow as better probes of QGP properties

In earlier studies we have proposed that most parton v2 comes from the anisotropic escape of partons, not from the hydrodynamic flow, even for semi-central Au+Au collisions at SNN = 200 GeV. Here we study the flavor dependence of this escape mechanism with a multi-phase transport model. In contrast to naive expectations, we find that the charm v2 is much more sensitive to the hydrodynamic flow than the lighter quark v2, and the fraction of v2 from the escape mechanism decreases strongly with the quark mass for large collision systems. We also find that the light quark collective flow is essential for the charm quark v2. Our finding thus suggests that heavy quark flows are better probes of the quark-gluon-plasma properties than light quark flows

Nuclear dependence of the transverse single-spin asymmetry in the production of charged hadrons at forward rapidity in polarized p+pp+p, p+p+Al, and p+p+Au collisions at sNN=200\sqrt{s_{_{NN}}}=200 GeV

We report on the nuclear dependence of transverse single-spin asymmetries (TSSAs) in the production of positively-charged hadrons in polarized $p^{\uparrow}+p$, $p^{\uparrow}+$Al and $p^{\uparrow}+$Au collisions at $\sqrt{s_{_{NN}}}=200$ GeV. The measurements have been performed at forward rapidity ($1.4<\eta<2.4$) over the range of $1.8<p_{T}<7.0$ GeV$/c$ and $0.1<x_{F}<0.2$. We observed a positive asymmetry $A_{N}$ for positively-charged hadrons in \polpp collisions, and a significantly reduced asymmetry in $p^{\uparrow}$+$A$ collisions. These results reveal a nuclear dependence of charged hadron $A_N$ in a regime where perturbative techniques are relevant. These results provide new opportunities to use \polpA collisions as a tool to investigate the rich phenomena behind TSSAs in hadronic collisions and to use TSSA as a new handle in studying small-system collisions.Comment: 303 authors from 66 institutions, 9 pages, 2 figures, 1 table. v1 is version accepted for publication in Physical Review Letters. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.htm