Nuclear Physics Seminars at BNL

Longitudinal double spin asymmetry for incluisve jet and dijet production in proton-proton collisions at $\sqrt{s} =$ 510 GeV

by Zilong Chang (BNL)

US/Eastern
Small Seminar Room

Small Seminar Room

Description

Jets productions from pp collisions at RHIC kinematics are dominated by quark-gluon and gluon-gluon scattering processes. Both of these longitudinal double spin dependent processes have sizable asymmetries in the pseudorapidity range, -1 < \eta < 1. Therefore the longitudinal double-spin asymmetry A_{LL} for jets is an effective channel to explore the gluon polarization in the proton.  Early STAR inclusive jet A_{LL} results at \sqrt{s} =  200 GeV provided the first evidence of the non-zero gluon polarization at x >  0.05. In this talk, we will report the first measurement of the midrapidity inclusive jet and dijet A_{LL} at \sqrt{s} = 510 GeV. The inclusive jet A_{LL} measurement provides sensitivity to the gluon helicity distribution down to a Bjorken-x of 0.015, while the dijet measurements, binned in four jet-pair topologies, will allow for tighter constraints on the x dependence. Both results are consistent with previous measurements made at \sqrt{s} = 200 GeV and show excellent agreement with predictions from recent next-to-leading order global analyses. In addition the new techniques designed for this analysis, for example, the underlying event correction to the jet transverse energy and its effect on the jet A_{LL} will be discussed.