Improved Measurement of Double Helicity Asymmetry in Inclusive Midrapidity pi^0 Production for Polarized p+p Collisions at sqrt(s)=200 GeV

TL;DR

This paper reports an improved measurement of double helicity asymmetry in pi^0 production in polarized proton-proton collisions at 200 GeV, utilizing enhanced data and calibration for more precise results.

Contribution

It introduces a more accurate measurement of helicity asymmetry using new data and recalibrated beam polarization, advancing understanding of gluon polarization in protons.

Findings

Reduced uncertainties in asymmetry measurements

Better agreement with NLO pQCD calculations

Enhanced data quality from the 2004 RHIC run

Abstract

We present an improved measurement of the double helicity asymmetry for pi^0 production in polarized proton-proton scattering at sqrt(s) = 200 GeV 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, 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.