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 ($A_{L}L$) of jet production in longitudinally polarized p+p collisions at $\sqrt{s}$=200 GeV. Photons and charged particles were measured at midrapidity $\mathrm{\mid }\eta \mathrm{\mid }<0.35$ 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 ($p_T^{\mathrm{r}\mathrm{e}\mathrm{c}\mathrm{o}}$). The effect of detector response and the underlying events on $p_T^{\mathrm{r}\mathrm{e}\mathrm{c}\mathrm{o}}$ was evaluated with the simulation. The production rate of reconstructed jets is satisfactorily reproduced with the NLO pQCD jet production cross section. For $4<p_T^{\mathrm{r}\mathrm{e}\mathrm{c}\mathrm{o}}<12$ GeV/$c$ with an average beam polarization of $<P>=49$ we measured $A_{LL} = -0.0014 \pm 0.0037^{\rm stat}$atthelowest$p_T^{\rm reco}$bin(4-5GeV\mathrm{/}$c$)and$-0.0181 \pm 0.0282^{\rm stat}$atthehighest$p_T^{\rm reco}$ bin (10-12 GeV/$c$) with a beam polarization scale error of 9.4% and a $\text{pT}$ scale error of 10%. Jets in the measured $p_T^{\mathrm{r}\mathrm{e}\mathrm{c}\mathrm{o}}$ 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 $\mathrm{\Delta }G(x)$ distributions based on the GRSV parameterization. The present result imposes the limit $-1.1 < \int_{0.02}^{0.3}dx \Delta G(x, \mu^2 = 1 {\rm GeV}^2) < 0.4$at95$\int_{0.02}^{0.3}dx \Delta G(x, \mu^2 = 1 {\rm GeV}^2) < 0.5$ at 99% confidence level.