Measurement of direct photon production in p + p collisions at sqrt(s) = 200 GeV

Cross sections for mid-rapidity production of direct photons in p+p collisions at the Relativistic Heavy Ion Collider (RHIC) are reported for 3 < p_T < 16 GeV/c. Next-to-leading order (NLO) perturbative QCD (pQCD) describes the data well for p_T > 5 GeV/c, where the uncertainties of the measurement and theory are comparable. We also report on the effect of requiring the photons to be isolated from parton jet energy. The observed fraction of isolated photons is well described by pQCD for p_T > 7 GeV/c.Comment: 330 authors, 6 pages text, 3 figures, one table. Submitted to Phys. Rev. Lett. 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

Elliptic flow for phi mesons and (anti)deuterons in Au+Au collisions at sqrt(s_NN) = 200 GeV

Differential elliptic flow (v_2) for phi mesons and (anti)deuterons (d^bar)d is measured for Au+Au collisions at sqrt(s_NN) = 200 GeV. The v_2 for phi mesons follows the trend of lighter pi^+/- and K^+/- mesons, suggesting that ordinary hadrons interacting with standard hadronic cross sections are not the primary driver for elliptic flow development. The v_2 values for (d^bar)d suggest that elliptic flow is additive for composite particles. This further validation of the universal scaling of v_2 per constituent quark for baryons and mesons suggests that partonic collectivity dominates the transverse expansion dynamics.Comment: 343 authors, 6 pages text, 3 figures, REVTeX4. To be submitted to 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

The Association Between Compulsory School Achievement and Problem Gambling Among Swedish Young People

Purpose: We aimed to examine the association between school grades at the age of 16 years and problem gambling at the age of 17-25 years among Swedish females and males. Methods: In a cohort design, we followed the 16-to 24-year-old participants in the representative Swedish Longitudinal Gambling Study for 2 years, 2008/2009 and 2009/2010, generating 3,816 person-years of follow-up time. The outcome, incidence of mild and moderate/severe gambling problems, was measured by the Problem Gambling Severity Index in telephone interviews. The exposure was register-linked information about final grades in compulsory school. The association between school grades and problem gambling was estimated in multinomial logistic regressions. Results: Low and average school grades were associated with increased incidence of mild and moderate/severe problem gambling compared to high grades, adjusted for sociodemographic characteristics, psychological distress, and alcohol use. Low grades, compared to high grades, were associated with a higher risk of mild gambling problems for adolescent males, whereas the incidence proportion of moderate/severe problem gambling was high for males aged 20-25 years with low grades, among whom unemployment was also very high. Furthermore, we found a strong and graded association between school grades and moderate/severe problem gambling for women in both age groups, despite a low prevalence of gambling participation among females compared to males. Conclusions: Our findings show that Swedish youth with low school achievement have an increased risk of gambling problems up to 8 years after school graduation, after control for confounding from sociodemographic characteristics, psychological distress, and alcohol use, and that this association is stronger for females than males

The Association Between Compulsory School Achievement and Problem Gambling Among Swedish Young People

Purpose: We aimed to examine the association between school grades at the age of 16 years and problem gambling at the age of 17-25 years among Swedish females and males. Methods: In a cohort design, we followed the 16-to 24-year-old participants in the representative Swedish Longitudinal Gambling Study for 2 years, 2008/2009 and 2009/2010, generating 3,816 person-years of follow-up time. The outcome, incidence of mild and moderate/severe gambling problems, was measured by the Problem Gambling Severity Index in telephone interviews. The exposure was register-linked information about final grades in compulsory school. The association between school grades and problem gambling was estimated in multinomial logistic regressions. Results: Low and average school grades were associated with increased incidence of mild and moderate/severe problem gambling compared to high grades, adjusted for sociodemographic characteristics, psychological distress, and alcohol use. Low grades, compared to high grades, were associated with a higher risk of mild gambling problems for adolescent males, whereas the incidence proportion of moderate/severe problem gambling was high for males aged 20-25 years with low grades, among whom unemployment was also very high. Furthermore, we found a strong and graded association between school grades and moderate/severe problem gambling for women in both age groups, despite a low prevalence of gambling participation among females compared to males. Conclusions: Our findings show that Swedish youth with low school achievement have an increased risk of gambling problems up to 8 years after school graduation, after control for confounding from sociodemographic characteristics, psychological distress, and alcohol use, and that this association is stronger for females than males

Scaling properties of azimuthal anisotropy in Au plus Au and Cu plus Cu collisions at root s(NN)=200 GeV

Differential measurements of elliptic flow (v(2)) for Au+Au and Cu+Cu collisions at root s(NN)=200 GeV are used to test and validate predictions from perfect fluid hydrodynamics for scaling of v(2) with eccentricity, system size, and transverse kinetic energy (KET). For KET equivalent to m(T)-m up to similar to 1 GeV the scaling is compatible with hydrodynamic expansion of a thermalized fluid. For large values of KET mesons and baryons scale separately. Quark number scaling reveals a universal scaling of v(2) for both mesons and baryons over the full KET range for Au+Au. For Au+Au and Cu+Cu the scaling is more pronounced in terms of KET, rather than transverse momentum

Correlated production of p and (p)over-bar in Au+Au collisions at root s(NN)=200 GeV

Correlations between p and (p) over bar at transverse momenta typical of enhanced baryon production in Au + Au collisions are reported. The PHENIX experiment has measured same and opposite sign baryon pairs in Au + Au collisions at root s(NN) = 200 GeV. Correlated production of p and p with the trigger particle from the range 2.5 < p(T) < 4.0 GeV/c and the associated particle with 1.8 < p(T) < 2.5 GeV/c is observed to be nearly independent of the centrality of the collisions. Same sign pairs show no correlation at any centrality. The conditional yield of mesons triggered by baryons (and anti-baryons) and mesons in the same p(T) range rises with increasing centrality, except for the most central collisions, where baryons show a significantly smaller number of associated mesons. These data are consistent with a picture in which hard scattered partons produce correlated p and (p) over bar in the p(T) region of the baryon excess. (c) 2007 Elsevier B.V. All rights reserved

Energy loss and flow of heavy quarks in Au+Au collisions at root s(NN) = 200 GeV

The PHENIX experiment at the BNL Relativistic Heavy Ion Collider (RHIC) has measured electrons with 0.3 < p(T) < 9 GeV/c at midrapidity (y < 0.35) from heavy-flavor (charm and bottom) decays in Au + Au collisions at root s(NN) = 200 GeV. The nuclear modification factor R-AA relative to p + p collisions shows a strong suppression in central Au + Au collisions, indicating substantial energy loss of heavy quarks in the medium produced at RHIC energies. A large azimuthal anisotropy v(2) with respect to the reaction plane is observed for 0.5 < p(T) < 5 GeV/c indicating substantial heavy-flavor elliptic flow. Both R-AA and v(2) show a p(T) dependence different from those of neutral pions. A comparison to transport models which simultaneously describe R-AA(p(T)) and v(2)(p(T)) suggests that the viscosity to entropy density ratio is close to the conjectured quantum lower bound, i.e., near a perfect fluid