Measurement of the Longitudinal Polarization of the HERA Electron Beam Using Crystals and the ZEUS Luminosity Monitor

TL;DR

This paper proposes a method to measure the longitudinal polarization of the HERA electron beam using crystal interactions, enabling independent verification and exploration of birefringence phenomena for high-energy photons.

Contribution

It introduces a novel polarization measurement technique leveraging crystal interactions, expanding capabilities for beam polarization verification at HERA.

Findings

Feasibility of polarization measurement with crystals demonstrated

Potential for independent polarization verification at HERA

Insights into birefringence phenomena for 20-30 GeV photons

Abstract

A measurement of the longitudinal polarization of the electron beam at HERA utilizing coherent interactions of high energy photons in crystals is proposed. Modification of existing facilities would allow an independent polarization measurement and a verification of birefringence phenomena in crystals for 20--30~GeV photons. Relevant experimental issues and systematic uncertainties are also presented.