Event Structure and Double Helicity Asymmetry in Jet Production from Polarized p+p Collisions at sqrt(s) = 200 GeV

We report on event structure and double helicity asymmetry (\(A_LL\)) of jet production in longitudinally polarized p+p collisions at \(\sqrt{s}\)=200 GeV. Photons and charged particles were measured at midrapidity \(|\eta| < 0.35\) with the requirement of a high-momentum (\(>2\) GeV/\(c\)) photon in each event. Measured event structure is compared with {\sc pythia} and {\sc geant} simulations. The shape of jets and the underlying event were well reproduced at this collision energy. For the measurement of jet \(A_{LL}\), photons and charged particles were clustered with a seed-cone algorithm to obtain the cluster \(p_T\) sum (\(p_T^{\rm reco}\)). The effect of detector response and the underlying events on \(p_T^{\rm reco}\) was evaluated with the simulation. The production rate of reconstructed jets is satisfactorily reproduced with the NLO pQCD jet production cross section. For \(4 < p_T^{\rm reco} < 12\) GeV/\(c\) with an average beam polarization of \(< P > = 49%\) we measured \(A_{LL} = -0.0014 \pm 0.0037^{\rm stat}\) at the lowest \(p_T^{\rm reco}\) bin (4-5 GeV/\(c\)) and \(-0.0181 \pm 0.0282^{\rm stat}\) at the highest \(p_T^{\rm reco}\) bin (10-12 GeV/\(c\)) with a beam polarization scale error of 9.4% and a \(\pT\) scale error of 10%. Jets in the measured \(p_T^{\rm reco}\) range arise primarily from hard-scattered gluons with momentum fraction \(0.02 < x < 0.3\) according to {\sc pythia}. The measured \(A_{LL}\) is compared with predictions that assume various \(\Delta G(x)\) distributions based on the GRSV parameterization. The present result imposes the limit \(-1.1 < \int_{0.02}^{0.3}dx \Delta G(x, \mu^2 = 1 {\rm GeV}^2) < 0.4\) at 95% confidence level or \(\int_{0.02}^{0.3}dx \Delta G(x, \mu^2 = 1 {\rm GeV}^2) < 0.5\) at 99% confidence level.