Heavy quarkonium production is not fully understood, but often described by two different models, the Color Singlet Model (CSM), and the Color Octet Model (COM). Previous measurements at the Tevatron collider by the CDF and D0 experiments are not fully in agreement with predicted observables from either model. The Relativistic Heavy Ion Collider (RHIC), and the Solenoidal Tracker At RHIC (STAR) is well suited to further explore heavy quarkonium production. The Heavy Flavor program in STAR encompasses various heavy-flavor analyses, taking advantage of its large solid-angle acceptance, including measurements that explore the properties of heavy quarkonium production using J/ψ and Upsilon (Υ) reconstructions via the di-electron channel, in p+p, d+Au, Cu+Cu, and Au+Au collision systems. This thesis presents results of reconstructed Upsilon (Υ) to study the Upsilon(nS) [n = 1, 2, 3] line- shape and measurements of the production-related observables of spin-alignment (‘polarization’) and Upsilon + hadron correlations (Υ + h) to investigate the Upsilon production mechanism, using triggered data from Run-8 (2008) d+Au and Run-9 (2009) p+p collisions at sqrt(sN N) = 200 GeV, detected at STAR. The result of the spin-alignment measurement is α = 1 ± 0.3 with χ^2 /n.d.f. = 18.71/7 indicating a large (transverse) polarization. The measurement of hadronic activity near the vicinity of an Upsilon, within current uncertainties, is in reasonable agreement with both CSM and COM predictions from PYTHIA, but slightly favors the COM prediction for the near-side Υ + h correlation.

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For over a decade studies of the strong interaction in extremely dense nuclear environments have been done at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory. It is hypothesized that colliding two beams of Au nuclei at relativistic speeds creates an environment of hot dense nuclear matter where the quarks and gluons inside the nucleus, which are normally confined within the protons and neutrons, become deconfined into a soup called the quark-gluon plasma. Since direct observation of this short-lived phase is impossible, many sophisticated analysis techniques attempt to study the early interactions via the final state particles. What has emerged from analyses of the data are two, contradictory paradigms for understanding the results. On the one hand the colliding quarks and gluons are thought to strongly interact and reach thermal equilibrium. The other view is that primary parton-parton scattering leads directly to jet fragmentation with little effect from re-scattering. It is in principle possible to distinguish and perhaps falsify one or both of these models of relativistic heavy ion collisions via the analysis of two-particle correlations among all charged particles produced in [mathematical symbols] = 200 GeV Au+Au collisions at the STAR experiment at RHIC. This dissertation presents studies of two-particle correlations, whose derivation can be traced back to Pearson's correlation coefficient, in transverse momentum and angular space. In momentum space a broad peak is observed extending from 0.5-4.0 GeV/c which, as a function of nuclear overlap, remains at a fixed position while monotonically increasing in amplitude. Comparisons to theoretical models suggests this peak is from jet fragmentation. In a complementary study the momentum distribution of correlations in ([eta],[phi]) space is investigated. The momentum distribution of correlated pairs that contribute to the peak near the origin, commonly associated with jet fragmentation, is peaked around 1.5 GeV/c and does not soften with increased centrality. These measurements present important aspects of the available six dimensional correlation space and provide definitive tests for theoretical models. Preliminary findings do not appear to support the hypothesis of a strongly interacting QGP where back-to-back jets are expected to be significantly suppressed. / text

One of the biggest quests in nuclear and particle physics in the last three decades is to unravel the spin structure of hadrons like protons and neutrons. Spin not only plays a central role in the strong force connecting the elementary constituents of matter, but is also responsible for many of its fundamental properties including the magnetic moment which defines the magnetic properties, the different phases in low temperature physics, and the stability of the universe in general. The origin of the spin of particles like protons and neutrons, which make up to 99.9% of the visible universe, has been the focus of experimental and theoretical efforts. Experiments at European Muon Collaboration (EMC) found that our knowledge of how the spin of the nucleon is derived from its elementary constituents is naive, and our interpretations are not valid. This was termed the spin crisis, an outstanding puzzle for more than three decades and is still not solved. Deciphering the spin puzzle requires knowing the spin of elementary constituents of these particles, quarks and gluons. One of the major objectives of the Relativistic Heavy Ion Collider (RHIC) spin program at Brookhaven National Laboratory is the measurement of the gluon helicity contribution to the proton spin via measuring the double helicity asymmetry (ALL) in various channels. In Pioneering High Energy Nuclear Interaction eXperiment (PHENIX) we measure ALL in π0 meson production. The π0 meson is reconstructed through its di-photon decay channel. The photons are detected by the PHENIX Electromagnetic Calorimeter, which consists of lead glass and lead scintillator detectors and covers a rapidity of |η|< 0.35 and azimuthal angle of 180°. In this dissertation, the results of ALLin π0 production from the data collected in 2013 at center of mass energy = 510 GeV are presented. In 2013, the total integrated luminosity is 150 pb-1 which is almost ten times the total luminosity recorded in 2009 at center of mass energy = 200 GeV. Due to the increase in the center of mass energy and integrated luminosity, these measurements cover the Bjorken x range down to ~0.01. A non-zero ALL result is observed that is consistent with positive gluon polarization in the probed kinematics.

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Understanding what contributes to the intrinsic angular momentum (spin) of the proton has been a major goal of the nuclear physics community. In the 1980s, it was discovered that quarks contribute 30% to the spin of the proton. This information led to a search to find other contributions to the spin of the proton. At STAR, the double spin asymmetry (ALL) is measured as it is sensitive to the polarized gluon distribution (Dg(x)). The STAR 2009 inclusive jet ALL at sqrt(s) = 200 GeV has been incorporated into two independent global fits. These fits show for the first time a statistically significant non-zero gluon contribution to the spin of the proton in the parton momentum fraction range x &gt; 0.05. Dijet ALL is also measured at STAR. Dijets are advantageous since the parton momentum fraction (x) of the initial partons may be reconstructed to first order from final state measurements. In 2013 STAR collected an estimated 250 pb-1 of data at sqrt(s) = 510 GeV. The higher center of mass energy will allow STAR to probe Dg(x) at x values as low as 0.02. The large statistics will allow a reduction in the uncertainties. Once the data is incorporated into future global fits, it will allow for a more precise determination of Dg(x). The 2013 dijet ALL results will be presented. The results show good agreement with both global fits and previous STAR results dijet measurements. / Physics

A large area time of flight (TOF) detector based on multi-gap resistive plate chamber (MRPC) technology has been developed for the STAR (Solenoidal Tracker at RHIC) experiment at the Relativistic Heavy Ion Collider at the Brookhaven National Laboratory, New York. The TOF detector replaces STAR's Central Trigger Barrel detector with 120 trays, each with 32 MRPCs. Each MRPC has 6 channels. The TOF detector improves by a factor of about 2 STAR's particle identification reach in transverse momenta and enhances STARs physics research program.