Cross section and double helicity asymmetry for η mesons and their comparison to π0 production at PHENIX

Abstract

The η cross section and double helicity asymmetry as a function of transverse momentum have been measured at √s = 200 GeV at the PHENIX experiment at RHIC. The cross section data serve as important input to the extraction of η fragmentation functions, which were essentially unknown before. With the availability of fragmentation functions the asymmetry data can be included in future pQCD fits in order to further constrain the polarized parton distribution functions, in particular the helicity-dependent gluon distribution function. In addition, the η to π0 cross section ratio as a function of transverse momentum has been extracted in a single pass over the same data set, thus minimizing systematic uncertainties. The inclusion of these data in future fragmentation function extractions should allow for more precise results for both particle species.