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This content will become publicly available on January 7, 2017

Title: Inclusive cross section and double-helicity asymmetry for $$\pi^{0}$$ production at midrapidity in $p$$+$$p$ collisions at $$\sqrt{s}=510$$ GeV

PHENIX measurements are presented 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 perturbativequantum- 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 π⁰ALL 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.
  1. Univ. of Colorado, Boulder, CO (United States); et al.
Publication Date:
OSTI Identifier:
Report Number(s):
Journal ID: ISSN 2470-0010; KB01-01-021
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Physical Review D
Additional Journal Information:
Journal Volume: 93; Journal ID: ISSN 2470-0010
American Physical Society (APS)
Research Org:
Brookhaven National Laboratory (BNL), Upton, NY (United States). Relativistic Heavy Ion Collider
Sponsoring Org:
USDOE Office of Science (SC), Nuclear Physics (NP) (SC-26)
Contributing Orgs:
PHENIX Collaboration
Country of Publication:
United States
73 NUCLEAR PHYSICS AND RADIATION PHYSICS cross section; double-helicity; midrapidity; collisions; Relativistic Heavy Ion Collider