Improved measurement of double helicity asymmetry in inclulsive midrapidity π0 production for polarized p+p collisions at s=200GeV

Abstract

We present an improved measurement of the double helicity asymmetry for π0 production in polarized proton-proton scattering at s=200GeV employing the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC). The improvements to our previous measurement come from two main factors: Inclusion of a new data set from the 2004 RHIC run with higher beam polarizations than the earlier run and a recalibration of the beam polarization measurements for the earlier run, which resulted in reduced uncertainties and increased beam polarizations. The results are compared to a Next to Leading Order (NLO) perturbative Quantum Chromodynamics (pQCD) calculation with a range of polarized gluon distributions. © 2006 The American Physical Society.