Centrality and Transverse Momentum Dependence of Elliptic Flow of Multistrange Hadrons and ϕ Meson in Au + Au Collisions at √ sNN = 200 GeV

We present high precision measurements of elliptic flow near midrapidity (|y|\u3c1.0) for multistrange hadrons and ϕ meson as a function of centrality and transverse momentum in Au+Au collisions at center of mass energy √sNN=200 GeV. We observe that the transverse momentum dependence of ϕ and Ω v2 is similar to that of π and p, respectively, which may indicate that the heavier strange quark flows as strongly as the lighter up and down quarks. This observation constitutes a clear piece of evidence for the development of partonic collectivity in heavy-ion collisions at the top RHIC energy. Number of constituent quark scaling is found to hold within statistical uncertainty for both 0%–30% and 30%–80% collision centrality. There is an indication of the breakdown of previously observed mass ordering between ϕ and proton v2 at low transverse momentum in the 0%–30% centrality range, possibly indicating late hadronic interactions affecting the proton v2

Jet-like Correlations with Direct-Photon and Neutral-Pion Triggers at sNN=200 GeV

Azimuthal correlations of charged hadrons with direct-photon (γdir) and neutral-pion (π0) trigger particles are analyzed in central Au+Au and minimum-bias p + p collisions at √sN N = 200 GeV in the STAR experiment. The charged-hadron per-trigger yields at mid-rapidity from central Au+Au collisions are compared with p + p collisions to quantify the suppression in Au+Au collisions. The suppression of the away-side associated-particle yields per γdir trigger is independent of the transverse momentum of the trigger particle (ptrig T ), whereas the suppression is smaller at low transverse momentum of the associated charged hadrons (passoc T ). Within uncertainty, similar levels of suppression are observed for γdir and π0 triggers as a function of zT (≡ passoc T /ptrig T ). The results are compared with energy-lossinspired theoretical model predictions. Our studies support previous conclusions that the lost energy reappears predominantly at low transverse momentum, regardless of the trigger energy

Measurement of the cross section and longitudinal double-spin asymmetry for dijet production in polarized pp collisions at √ s = 200 GeV

We report the first measurement of the longitudinal double-spin asymmetry ALL for midrapidity dijet production in polarized pp collisions at a center-of-mass energy of √s=200 GeV. The dijet cross section was measured and is shown to be consistent with next-to-leading order (NLO) perturbative QCD predictions. ALL results are presented for two distinct topologies, defined by the jet pseudorapidities, and are compared to predictions from several recent NLO global analyses. The measured asymmetries, the first such correlation measurements, support those analyses that find positive gluon polarization at the level of roughly 0.2 over the region of Bjorken-x\u3e0.05

Precision Measurement of the Longitudinal Double-Spin Asymmetry for Inclusive Jet Production in Polarized Proton Collisions at s√=200 GeV

We report a new measurement of the midrapidity inclusive jet longitudinal double-spin asymmetry, ALL, in polarized pp collisions at center-of-mass energy s√=200  GeV. The STAR data place stringent constraints on polarized parton distribution functions extracted at next-to-leading order from global analyses of inclusive deep-inelastic scattering (DIS), semi-inclusive DIS, and RHIC pp data. The measured asymmetries provide evidence at the 3σ level for positive gluon polarization in the Bjorken-x region x\u3e0.05

Photograph presentation order and range effects in visual based outdoor recreation research

2011 Spring.Includes bibliographical references.Visual based research methods, referring to the use of visual images to represent recreation resource conditions, are commonly used in outdoor recreation research to investigate appropriate levels of visitor use. Visual methods were developed to allow for the simulation of recreation resource conditions that would be difficult to describe using narrative methods. The research contained in this dissertation builds on previous research related to visual based methods of outdoor recreation. While data from visual based research methods can provide a strong empirical basis to support outdoor recreation management decision-making, visual research methods applied in this context are subject to several potential sources of measurement bias. These potential sources of bias include effects associated with photograph presentation order, and effects associated with the range of resource conditions depicted. These two biases are respectively referred to as order effect and range effect. This dissertation examines the issues of order and range effect biases in visual based outdoor recreation research. In a lab setting, respondents were asked to rate a series of photographs of a recreation site in Rocky Mountain National Park in terms if the acceptability of the number of people at one time (PAOT) as depicted in the photographs. In order to test for order effects, respondents were separated into six groups where photograph presentation order differed for each group. Results from qualitative and quantitative analyses indicate photograph presentation order significantly affected photograph acceptability ratings. In order to test for range effects, respondents were divided into seven groups where PAOT range differed for each group. Results from qualitative and quantitative analyses indicate range significantly affected photograph acceptability ratings. Results from the investigations of order and range effects suggest a number of different principles that could be applied to future studies employing visual based methods. These principles are discussed along with future avenues of research that were uncovered through the course of the investigations of order and range effect biases

Measurement of D0 Azimuthal Anisotropy at Midrapidity in Au + Au Collisions at √ s N N = 200 GeV

We report the first measurement of the elliptic anisotropy (v2) of the charm meson D0 at midrapidity (|y

Investigating evolutionary rate variation in bacteria

Rates of molecular evolution are known to vary between species and across all kingdoms of life. Here, we explore variation in the rate at which bacteria accumulate mutations (accumulation rates) in their natural environments over short periods of time. We have compiled estimates of the accumulation rate for over 34 species of bacteria, the majority of which are pathogens evolving either within an individual host or during outbreaks. Across species, we find that accumulation rates vary by over 3700-fold. We investigate whether accumulation rates are associated to a number potential correlates including genome size, GC content, measures of the natural selection and the time frame over which the accumulation rates were estimated. After controlling for phylogenetic non-independence, we find that the accumulation rate is not significantly correlated to any factor. Furthermore, contrary to previous results, we find that it is not impacted by the time frame of which the estimate was made. However, our study, with only 34 species, is likely to lack power to detect anything but large effects. We suggest that much of the rate variation may be explained by differences between species in the generation time in the wild