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Inclusive double-helicity asymmetries in neutral pion and eta meson production in $\vec{p}+\vec{p}$ collisions at $\sqrt{s}=200$ GeV

Abstract

Results are presented from data recorded in 2009 by the PHENIX experiment at the Relativistic Heavy Ion Collider for the double-longitudinal spin asymmetry, , for and production in GeV polarized collisions. Comparison of the results with different theory expectations based on fits of other published data showed a preference for small positive values of gluon polarization, , in the proton in the probed Bjorken range. The effect of adding the new 2009 \pz data to a recent global analysis of polarized scattering data is also shown, resulting in a best fit value in the range , with the uncertainty at when considering only statistical experimental uncertainties. Shifting the PHENIX data points by their systematic uncertainty leads to a variation of the best-fit value of between and , demonstrating the need for full treatment of the experimental systematic uncertainties in future global analyses.