Double Helicity Asymmetries of Forward Neutral Pions from s = 510 GeV pp Collisions at STAR

Abstract

Longitudinally polarized [Formula: see text] scattering experiments provide access to gluon polarization via measurement of the double helicity asymmetry, [Formula: see text]. At the completion of the 2013 RHIC running period, a significant dataset of [Formula: see text]s corresponding to an integrated luminosity of 46 [Formula: see text] (2012) and 8 [Formula: see text] (2013) produced from polarized [Formula: see text] scattering at [Formula: see text] GeV with an average beam polarization of approximately [Formula: see text] was acquired. The [Formula: see text] kinematics were measured via isolation cones by the STAR Forward Meson Spectrometer, an electromagnetic calorimeter covering a forward pseudorapidity range of [Formula: see text]. The asymmetric [Formula: see text] subprocess becomes more dominant in this forward region than in the midrapidity region; furthermore, asymmetry measurements in the forward region are sensitive to low-[Formula: see text] gluons. Progress on [Formula: see text] determined from forward [Formula: see text] events, complementing previous midrapidity measurements, are presented.