Inclusive cross section and double helicity asymmetry for pi^0 production in p+p collisions at sqrt(s) = 62.4 GeV

TL;DR

This paper reports measurements of inclusive pi^0 production and double helicity asymmetry in polarized proton collisions at 62.4 GeV, providing insights into gluon polarization and testing pQCD predictions.

Contribution

It provides the first measurements of pi^0 cross sections and asymmetries at this energy, improving understanding of gluon polarization and validating pQCD calculations with higher precision.

Findings

Unpolarized cross sections agree with pQCD predictions when including logarithmic corrections.

Double helicity asymmetries constrain gluon polarization for 0.06 < x_g < 0.4.

Results enhance understanding of proton spin structure at intermediate energies.

Abstract

The PHENIX experiment presents results from the RHIC 2006 run with polarized proton collisions at sqrt(s) = 62.4 GeV for inclusive pi^0 production at mid-rapidity. Unpolarized cross section results are measured for transverse momenta p_T = 0.5 to 7 GeV/c. Next-to-leading order perturbative quantum chromodynamics calculations are compared with the data, and while the calculations are consistent with the measurements, next-to-leading logarithmic corrections improve the agreement. Double helicity asymmetries A_LL are presented for p_T = 1 to 4 GeV/c and probe the higher range of Bjorken_x of the gluon (x_g) with better statistical precision than our previous measurements at sqrt(s)=200 GeV. These measurements are sensitive to the gluon polarization in the proton for 0.06 < x_g < 0.4.