Measurement of the Transverse Single Spin Asymmetry of $p$ + $p^\uparrow$ $\rightarrow$ $\eta$ + $X$ at $\sqrt{s}$ = 200 GeV

TL;DR

This paper reports on the measurement of the transverse single spin asymmetry ($A_N$) for $ ext{p} + ext{p}^rrow ext{$ ext{ exteta}$} + X$ at 200 GeV, providing insights into nucleon structure and spin effects.

Contribution

It presents the first measurement of $A_N$ for $ ext{ exteta}$ mesons at forward rapidity in polarized proton collisions at RHIC.

Findings

Significant asymmetries observed in forward region.

Results help constrain models involving Sivers and Collins effects.

Data supports further understanding of nucleon spin structure.

Abstract

The measurement of transverse single spin asymmetries ($A_N$) provides insight into the structure of the nucleon. Several mechanisms have been proposed that attempt to explain $A_N$ based on QCD, and additional measurements of $A_N$ for different processes further constrain these models. Using the PHENIX detector at the Relativistic Heavy Ion Collider (RHIC), we study transversely polarized p+p collisions. Results from PHENIX and other experiments show significant asymmetries in the forward region, which could be due to contributions from both the Sivers and the Collins effects. Studying the species as well as the kinematic dependencies of these transverse single spin asymmetries will help to disentangle the origin of the observed asymmetries. Therefore, measurements of $A_N$ with inclusive $\eta$ mesons at forward rapidities are an important tool for the understanding of these asymmetries. In 2008, the PHENIX experiment collected 5.2 pb$^{-1}$ integrated luminosity in $p^\uparrow+p$ collisions at $\sqrt{s}$ = 200 GeV. The status of the asymmetry analysis of $\eta$ mesons at forward rapidity will be shown.