Nuclear Physics Seminar

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

Presented by Zilong Chang, BNL

Tuesday, September 10, 2019, 11:00 am — Small Seminar Room, Bldg. 510

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.

Hosted by: Rongrong Ma

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