Charged Antiparticle to Particle Ratios Near Midrapidity in d+Au and p+p Collisions at sqrt(s_NN) = 200 GeV

Experiments at the Relativistic Heavy Ion Collider (RHIC) at Brookhaven National Laboratory are designed to investigate the behavior of strongly interacting matter at high temperatures and densities. The conditions created during a heavy ion collision at RHIC energies are predicted to be sufficient to form a quark-gluon plasma. As part of this investigation, smaller collision systems need to be studied to aid in the understanding and interpretation of results from the more complicated heavy ion collisions. This thesis reports the ratios of the yields of antiparticles to particles for primary charged pions, kaons, and protons emitted in p+p and d+Au collisions at sqrt{s_NN}=200GeV. In the d+Au collision system the results are measured as a function of collision centrality. The data analyzed were collected by the PHOBOS detector during the 2003 run of the Relativistic Heavy Ion Collider. Comparison of the results obtained in this thesis with the antiparticle to particle ratios measured in 200GeV Au+Au collisions allows the effects of final state interactions on the produced particle yields to be inferred. Furthermore, measurement of the antiproton to proton ratio allows the relative influence of the baryon number transport and the antibaryon-baryon pair production mechanisms on the collision process to be investigated. The measured antiparticle to particle ratios represent the ratio of the yields averaged over the rapidity range of 0.1<y_pi<1.3 and 0<y_{K,p}<0.8, and for transverse momenta of 0.1<p_{T}^{pi,K}<1.0GeV/c and 0.3<p_{T}^p<1.0GeV/c. In the d+Au collision system it is found that the relative yields of antiparticles to particles are independent of centrality for all three particle species, pions, kaons and protons. The <pi-/pi+> ratio at all centralities is consistent with one. In the top 10% most central events <pi-/pi+>=1.016+/-0.007(stat.)+/-0.019(syst.) and in the 60-100% most peripheral events <pi-/pi+>=0.996+/-0.008(stat.)+/-0.013(syst.). The <K-/K+> ratio ranges from 0.97+/-0.03(stat.)+/-0.04(syst.) in the top 10% most central events to 1.00+/-0.04(stat.)+/-0.03(syst.) in the 60-100% most peripheral events. The <pbar/p> ratio ranges from 0.86+/-0.02(stat.)+/-0.04(syst.) in the top 10% most central events to 0.85+/-0.02(stat.)+/-0.03(syst.) in the 60-100% most peripheral events. The results obtained for the p+p collision system are consistent with the values measured in d+Au collisions. Ratios of <pi-/pi+>=1.000+/-0.012(stat.)+/-0.019(syst.), <K-/K+>=0.93+/-0.05(stat.)+/-0.03(syst.), and <pbar/p>=0.85+/-0.04(stat.)+/-0.03(syst.) have been measured. The data are compared to results from model calculations, other collision systems and other collision energies

Heavy Quarkonia Production in p+p Collisions from the PHENIX Experiment

Quarkonia provide a sensitive probe of the properties of the hot dense medium created in high energy heavy ion collisions. Hard scattering processes result in the production of heavy quark pairs that interact with the collision medium during hadronization. These in-medium interactions convey information about the fundamental properties of the medium itself and can be used to examine the modification of the QCD confining potential in the collision environment. Baseline measurements from p+p and d+Au collision systems are used to distinguish cold nuclear matter effects while measurements from heavy ion collision systems are used to quantify in-medium effects. The PHENIX experiment has the capability of detecting heavy quarkonia at $1.2<|\eta|<2.2$ via the $\mu^+\mu^-$ decay channel and at $|\eta|<0.35$ via the $e^+e^-$ decay channel. Recent runs have resulted in the collection of high statistics p+p data sets that provide an essential baseline reference for heavy ion measurements and allow for further critical evaluation of heavy quarkonia production mechanisms. The latest PHENIX results for the production of the $J/\psi$ in p+p collisions are presented and future prospects for $\psi'$, $\chi_{c}$ and $\Upsilon$ measurements are discussed.Comment: 4 pages, 2 figures, Proceedings for Quark Matter 200

Quarkonium Production in PHENIX

Quarkonia provide a sensitive probe of the properties of the hot dense medium created in high energy heavy ion collisions. Hard scattering processes result in the production of heavy quark pairs that interact with the collision medium during hadronization. These in medium interactions convey information about the fundamental properties of the medium itself and can be used to examine the modification of the QCD confining potential in the collision environment. Baseline measurements from the d+Au and p+p collision systems can be used to distinguish cold nuclear matter effects while measurements from heavy ion collision systems, Au+Au and Cu+Cu, can be used to quantify in-medium effects. PHENIX results for the production of the $J/\psi$ for a diverse set of collision systems and energies and for the $\Upsilon$ in p+p collisions are presented.Comment: 9 pages, 7 figures, Proceedings for Hard Probes 200

Neutron Energy Spectrum Characterization on TMR-1 at the Indiana University Neutron Source

The energy spectrum of the Neutron Radiation Effects Program (NREP) beam line, Target-Moderator-Reflector-1 (TMR-1), at Indiana University has not been previously characterized. The facility has a unique proton source with variable pulse length (15-600 ms) and energy (13 MeV). Thus, it can produce a unique and tailored neutron beam when incident on a beryllium target. Through a combination of MCNP-X particle simulations, neutron activation experiments, and application of a spectrum unfolding code (SAND-II), the neutron source is characterized. Eight activation foils and wires were irradiated in the target area and the gamma activity measured. This information was used in an unfolding code, SAND-II, to deconvolve the spectrum, using the MCNP simulations as a basis for the spectral fitting

Nuclear Data Covariance Analysis in Radiation-Transport Simulations Utilizing SCALE Sampler and the IRDFF Nuclear Data Library

This article describes the nuclear data covariance analysis of an experimental design for a neutron energy-tuning assembly (ETA) created to shape a 14-MeV neutron point source to an objective spectrum. Underlying nuclear data uncertainties play a large role in the radiation transport and reaction rates for the range of responses to be expected from an experiment. The methodology leveraged the Standardized Computer Analysis for Licensing Evaluation (SCALE) Sampler module to determine the uncertainty in the neutron transport. The reaction uncertainty was perturbed with the International Reactor Dosimetry and Fusion File v.1.05 uncertainty, correlation matrix, and reaction cross section through multivariate normal distribution sampling to provide a final response metric. The resultant neutron fluence uncertainty for the ETA ranged from 2.7% to 6.2% in the energy range from 1.28 keV to 14.1 MeV, which contains 99.99% of the neutron fluence. The integrated uncertainties, including statistical and systematic nuclear data uncertainties, for the reaction products analyzed were 2.33% to 4.84% for most reactions, but 55Mn(n, γ), a less well-characterized reaction occurring in an energy domain with high flux uncertainty, was 19.7%. The mean of the reaction distributions was within 1.1% of the unperturbed nuclear data simulation. The experiment is planned for late 2019, where the predicted results will be compared against the experimental outcomes. The methodology presented can be utilized with alternate nuclear libraries in SCALE to develop uncertainty bounds and neutron flux spectra for many radiation-transport problems