Transverse Single Spin Asymmetries and Cross-Sections for Forward pi0 and eta Mesons at Large Feynman-x in sqrt(s)=200 GeV polarized p+p Collisions at STAR

TL;DR

This paper reports measurements of transverse single spin asymmetries and production cross-sections for forward pi0 and eta mesons at high Feynman-x in polarized proton-proton collisions at 200 GeV, providing insights into spin effects in QCD.

Contribution

It presents the first combined measurements of A_N and cross-sections for pi0 and eta mesons at large xF in polarized p+p collisions, including calibration and analysis methods.

Findings

Large A_N observed for eta mesons at xF > 0.5.

Cross-sections consistent with perturbative QCD predictions.

Enhanced understanding of spin asymmetries in forward meson production.

Abstract

The STAR collaboration has previously reported a large transverse single spin asymmetry, A_N, for forward pi0 meson production. The cross-section in this region was measured up to Feynman-x (xF) of 0.55, and found to be consistent with perturbative Quantum Chromo-Dynamics predictions. During RHIC running in the year 2006 (6.8 inverse-pb, 56 % average polarization), an even larger A_N was observed for the eta meson at forward rapidity for xF > 0.5. All data were collected by the STAR Forward Pion Detector during sqrt(s) = 200 GeV polarized p+p collisions at RHIC. Understanding these large spin asymmetries requires information on the production cross-section. In this thesis, we present the results of the cross-section as well as the A_N measurements for both pi0 and eta mesons at average pseudo-rapidity of 3.7, for 0.4 < xF < 0.75. The details of the calibration, and the analysis methods are also discussed. Finally, we present selected aspects of the high voltage system for the STAR Forward Meson Spectrometer inner calorimeter, which was designed primarily by the author and his thesis advisor.