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Measurements of double-helicity asymmetries for inclusive hadron production in polarized p+p collisions are sensitive to helicity--dependent parton distribution functions, in particular to the gluon helicity distribution, Delta(g). This study focuses on the extraction of the double-helicity asymmetry in eta production: polarized p+p --> eta + X, the eta cross section, and the eta/pi^0 cross section ratio. The cross section and ratio measurements provide essential input for the extraction of fragmentation functions that are needed to access the helicity-dependent parton distribution functions.
Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, $A_{LL}$, for $pi^0$ and $eta$ production in $sqrt{s} = 200$ GeV polarized $p$$+$$p$ collisio
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
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 I
We present a measurement of the cross section and transverse single-spin asymmetry ($A_N$) for $eta$ mesons at large pseudorapidity from $sqrt{s}=200$~GeV $p^{uparrow}+p$ collisions. The measured cross section for $0.5<p_T<5.0$~GeV/$c$ and $3.0<|eta|
We report on event structure and double helicity asymmetry ($A_LL$) of jet production in longitudinally polarized p+p collisions at $sqrt{s}$=200 GeV. Photons and charged particles were measured at midrapidity $|eta| < 0.35$ with the requirement of a