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

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.

389 authors, 4 pages, 2 tables, 1 figure. Submitted to Phys. Rev. D, Rapid Communications. Plain text data tables for the points plotted in figures for this and previous PHENIX publications are (or will be) publicly available at http://www.phenix.bnl.gov/papers.html

Cited by in corpus (12)

• A first unbiased global determination of polarized PDFs and their uncertainties
• Inclusive cross section and double helicity asymmetry for π^0 production in p+p collisions at sqrt(s)=200 GeV: Implications for the polarized gluon distribution in the proton
• Longitudinal double-spin asymmetry and cross section for inclusive jet production in polarized proton collisions at sqrt(s) = 200 GeV
• Spin Structure of the Nucleon - Status and Recent Results
• Anti-Hyperon polarization in high energy pp collisions with polarized beams
• First Extraction of Transverse Momentum Dependent Helicity Distributions
• Exploring the polarization of gluons in the nucleon
• Extraction of characteristic constants in QCD with perturbative and nonperturbative methods
• Hadron-Pair Photoproduction in Longitudinally Polarized Lepton-Nucleon Collisions
• Towards an understanding of nucleon spin structure: from hard to soft scales
• Recent Results from RHIC & Some Lessons for Cosmic-Ray Physicists
• Intrinsic parton motion soft mechanisms and the longitudinal spin asymmetry A_LL in high energy pp -> pi X