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PHENIX measurements are presented for the cross section and double-helicity asymmetry ($A_{LL}$) in inclusive $pi^0$ production at midrapidity from $p$$+$$p$ collisions at $sqrt{s}=510$~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 $pi^{0}A_{LL}$ results follow an increasingly positive asymmetry trend with $p_T$ and $sqrt{s}$ with respect to the predictions and are in excellent agreement with the latest global analysis results. This analysis incorporated earlier results on $pi^0$ and jet $A_{LL}$, and suggested a positive contribution of gluon polarization to the spin of the proton $Delta G$ for the gluon momentum fraction range $x>0.05$. The data presented here extend to a currently unexplored region, down to $xsim0.01$, and thus provide additional constraints on the value of $Delta G$. The results confirm the evidence for nonzero $Delta G$ using a different production channel in a complementary kinematic region.
The PHENIX experiment presents results from the RHIC 2006 run with polarized proton collisions at sqrt(s) = 62.4 GeV for inclusive pi^0 production at mid-rapidity. Unpolarized cross section results are measured for transverse momenta p_T = 0.5 to 7 G
Unpolarized cross sections and double-helicity asymmetries of single-inclusive positive and negative charged hadrons at midrapidity from p+p collisions at sqrt(s)=62.4 GeV are presented. The PHENIX measurements for 1.0 < p_T < 4.5 GeV/c are consisten
We present the midrapidity charged pion invariant cross sections and the ratio of $pi^-$-to-$pi^+$ production ($5<p_T<13$ GeV/$c$), together with the double-helicity asymmetries ($5<p_T<12$ GeV/$c$) in polarized $p$$+$$p$ collisions at $sqrt{s} = 200
We report the double helicity asymmetry, $A_{LL}^{J/psi}$, in inclusive $J/psi$ production at forward rapidity as a function of transverse momentum $p_T$ and rapidity $|y|$. The data analyzed were taken during $sqrt{s}=510$ GeV longitudinally polariz
The differential cross section for the production of direct photons in p+p collisions at sqrt(s)=200 GeV at midrapidity was measured in the PHENIX detector at the Relativistic Heavy Ion Collider. Inclusive-direct photons were measured in the transver