644 research outputs found
Inclusive cross section and double-helicity asymmetry for production at midrapidity in collisions at GeV
PHENIX measurements are presented for the cross section and double-helicity
asymmetry () in inclusive production at midrapidity from
collisions at ~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
results follow an increasingly positive asymmetry trend with
and with respect to the predictions and are in excellent
agreement with the latest global analysis results. This analysis incorporated
earlier results on and jet , and suggested a positive
contribution of gluon polarization to the spin of the proton for the
gluon momentum fraction range . The data presented here extend to a
currently unexplored region, down to , and thus provide additional
constraints on the value of . The results confirm the evidence for
nonzero using a different production channel in a complementary
kinematic region.Comment: 413 authors, 8 pages, 4 figures. v2 is version accepted as PRD Rapid
Communication. Plain text data tables for the points plotted in figures for
this and previous PHENIX publications are (or will be) publicly available at
http://www.phenix.bnl.gov/papers.htm
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