Local Polarimetry for Proton Beams with the STAR Beam Beam Counters

TL;DR

This paper presents the first local polarimeter at STAR using Beam-Beam Counters to measure single transverse spin asymmetries in proton-proton collisions, aiding in polarization control and verification.

Contribution

Introduction of a local polarimeter at STAR utilizing Beam-Beam Counters for real-time polarization measurements in proton collisions.

Findings

Measured asymmetries of about 0.01 at high pseudorapidities

Asymmetries at lower pseudorapidities are consistent with zero

The setup successfully tuned spin rotator magnets and verified polarization

Abstract

STAR collected data in proton-proton collisions at sqrt(s)=200 GeV with transverse and longitudinal beam polarizations during the 2003 running period at RHIC. We present preliminary results on single transverse spin asymmetries A_N in the production of forward charged hadrons detected with the Beam-Beam Counters (BBC). The asymmetries A_N measured at pseudorapidities 3.9 < |eta| < 5.0 are found to be of the order of 0.01 while asymmetries measured at smaller pseudorapidities 3.4 < |eta| < 3.9 are found to be consistent with zero. The BBC and its associated scaler system for fast data recording provides the first local polarimeter at STAR. The setup has been sucessfully used to tune the spin rotator magnets and to verify longitudinal polarization at STAR.