Cross section and double helicity asymmetry for eta mesons and their comparison to neutral pion production in p+p collisions at sqrt(s)=200 GeV

TL;DR

This paper reports measurements of double-helicity asymmetries for eta meson production in polarized proton-proton collisions at 200 GeV, providing insights into gluon polarization and fragmentation functions.

Contribution

It presents the first extraction of double-helicity asymmetry for eta mesons and compares it to neutral pion production, aiding in understanding gluon helicity distribution.

Findings

Measured eta cross section and asymmetry.

Provided eta/pi^0 cross section ratio.

Supplies data for fragmentation function extraction.

Abstract

Measurements of double-helicity asymmetries for inclusive hadron production in polarized p+p collisions are sensitive to helicity--dependent parton distribution functions, in particular to the gluon helicity distribution, Delta(g). This study focuses on the extraction of the double-helicity asymmetry in eta production: polarized p+p --> eta + X, the eta cross section, and the eta/pi^0 cross section ratio. The cross section and ratio measurements provide essential input for the extraction of fragmentation functions that are needed to access the helicity-dependent parton distribution functions.