Longitudinal double spin asymmetry for inclusive jet production in polarized proton-proton collisions at [square root of] s = 200 GeV

Abstract

We present the Inclusive Jet Longitudinal Double-Spin Asymmetry for polarized protons at \s = 200 GeV. The data were taken on the STAR experiment at RHIC during the 2005 run period and cover a jet transverse momentum range of 5 < pT < 30 GeV/c. The main detector components used were the time-projection chamber (TPC), barrel-electromagnetic calorimeter (BEMC), and beam-beam counters (BBC). Comparison of the asymmetry with theoretical calculations, which utilized deep inelastic scattering results, places constraints on the gluon contribution to the proton's spin. The asymmetry is consistent with prior measurements and further constrains the gluon's contribution over previous results. AG, a measure of the gluon's contribution, is restricted to less than 65% of the proton's spin at 90% confidence level. We also present the Inclusive Jet Cross-Section for unpolarized proton-proton collisions at v = 200 GeV. It covers a transverse momentum range of 5 < pT < 49 GeV/c. The cross-section is calculated for five triggers and the five triggers show good agreement among the cross-section results. The cross-section is compared with theoretical predictions based on NLO pQCD using the CTEQ6M parton distribution functions. The cross-section agrees with theoretical predictions when the uncertainty in jet momentum is taken into account. The cross-section is within the systematic uncertainties of previous measurements. The largest systematic uncertainty for the cross-section is due to the jet energy scale. This uncertainty ranges varies from 1.5% to 38% depending on the trigger and transverse momentum range.