Systematic error analysis in the absolute hydrogen gas jet polarimeter at RHIC

TL;DR

This paper presents a detailed systematic error analysis of the HJET polarimeter at RHIC, highlighting recent upgrades that improved measurement precision of proton beam polarization and analyzing power, with implications for future EIC applications.

Contribution

The paper provides a comprehensive systematic error analysis of the HJET polarimeter, including recent upgrades and their impact on measurement accuracy at RHIC.

Findings

Proton beam polarization measured at about 55% with 2% statistical and 0.3% systematic errors.

Elastic pp analyzing power determined with high precision, around 0.04 with an uncertainty of 0.0002.

Upgrades significantly reduced errors, enhancing the polarimeter's performance for future collider experiments.

Abstract

The Polarized Atomic Hydrogen Gas Jet Target polarimeter (HJET) is operated at the Relativistic Heavy Ion Collider (RHIC) since 2004 to measure the absolute polarization of each colliding proton beam. Polarimeter detectors and data acquisition were upgraded in 2015 to increase the solid angle, energy range, and to improve the energy and time resolution. These upgrades along with an improved beam intensity and polarization allowed us to greatly reduce the statistical and systematic errors for the proton polarization measurements in RHIC Runs 15 ($E_\text{beam}\!=\!100~\text{GeV}$) and 17 ($255~\text{GeV}$). For a typical 8 hour RHIC store, the measured proton beam average polarization was about $P_\text{beam}\!\sim\!55\pm2.0_\text{stat}\pm0.3_\text{syst}\%$. The elastic $\mathit{pp}$ analyzing power, $A_\text{N}(t)\!\sim\!0.04$, was determined with a precision of about $|\delta A_\text{N}(t)|\!\sim\!0.0002$ in the momentum transfer squared range $0.001\!<\!-t\!<\!0.020\,\text{GeV}^2$. In this paper we present a detailed systematic error analysis of the polarization measurements at HJET. Perspectives of using the HJET based absolute polarimeters in the future Electron Ion Collider (EIC) will be also discussed.