Feasibility study for precisely measuring the EIC ${}^3$He beam polarization with the Polarized Atomic Hydrogen Gas Jet Target polarimeter at RHIC

TL;DR

This study explores using the HJET polarimeter at RHIC to accurately measure the polarization of ${}^3$He beams at the EIC, demonstrating that systematic uncertainties can meet the required 1% precision.

Contribution

It proposes a method to adapt the HJET polarimeter for ${}^3$He beam polarization measurements with controlled systematic uncertainties.

Findings

Corrections due to absorption and breakup cancel in the ratio.

Hadronic spin-flip amplitude corrections can be derived from proton measurements.

Systematic uncertainty can meet the EIC requirement of less than 1%.

Abstract

The Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is used to measure the absolute proton beam polarization, $\sigma_P^\text{syst}/P\!\lesssim\!0.5\%$, at the Relativistic Heavy Ion Collider. Here I consider the possibility of employing HJET to measure the ${}^3\text{He}$ ($h$) beam polarization at the Electron-Ion Collider (EIC). The dominant contribution to the ratio of the $h^\uparrow{p}$ and $p^\uparrow{h}$ analyzing powers, which is needed for such measurements, can be easily calculated using well-known values of the proton and helion magnetic moments, but some corrections should be applied to achieve the required accuracy. It was found that corrections due to absorption and ${}^3\text{He}$ breakup effectively cancel in the ratio and a correction due to hadronic spin-flip amplitudes can be derived from the proton beam measurements. As a result, the anticipated systematic uncertainty in the measured ${}^3\text{He}$ beam polarization can satisfy the EIC requirement $\sigma_P^\text{syst}/P\!\lesssim\!1\%$.