Nuclear Physics Seminars
Friday, February 19, 2016
Physics Building, Room 313
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[Host: Donal Day]
Georgia State University
"Does the Gluon Carry Proton's Spin"
I will present the PHENIX measurements for the cross section and double-helicity asymmetry (ALL) in inclusive π0 production at midrapidity from p + p collisions at √s = 510 GeV from data taken in 2012 and 2013 at the Relativistic Heavy Ion Collider. The next-to-leading-order perturbative-quantum chromodynamics theory calculation is in excellent agreement with the presented cross section results. The calculation utilized parton-to-pion fragmentation functions from the recent DSS14 global analysis, which prefer a smaller gluon-to-pion fragmentation function. The π0 ALL results follow an increasingly positive asymmetry trend with pT and √s with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on π0 and jet ALL and suggested a positive contribution of gluon polarization to the spin of the proton ΔG for the gluon momentum fraction range x > 0.05. The data presented here extend to a currently unexplored region, down to x ∼ 0.01, and thus provide additional constraints on the value of ΔG.
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