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 ($p_T^{
m reco}$). The effect of detector response and the underlying
events on $p_T^{
m reco}$ was evaluated with the simulation. The production
rate of reconstructed jets is satisfactorily reproduced with the NLO pQCD jet
production cross section. For $4 < p_T^{
m reco} < 12$ GeV/$c$ with an average
beam polarization of $< P > = 49%$ we measured $A_{LL} = -0.0014 pm
0.0037^{
m stat}$ at the lowest $p_T^{
m reco}$ bin (4-5 GeV/$c$) and
$-0.0181 pm 0.0282^{
m stat}$ at the highest $p_T^{
m reco}$ 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 $p_T^{
m reco}$ 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 $-1.1 < int_{0.02}^{0.3}dx Delta G(x, mu^2 = 1 {
m
GeV}^2) < 0.4$ at 95% confidence level or $int_{0.02}^{0.3}dx Delta G(x,
mu^2 = 1 {
m GeV}^2) < 0.5$ at 99% confidence level.
Note: answers to reviews or questions about the article must be posted in the forum section.
Authors are not allowed to review their own article. They can use the forum section.