The HERMES Spectrometer

TL;DR

The HERMES spectrometer is a sophisticated detector system designed to study the spin structure of the nucleon through deep inelastic scattering experiments with polarized particles, featuring advanced tracking and particle identification capabilities.

Contribution

This paper introduces the design and features of the HERMES spectrometer, enabling precise measurements of polarized deep inelastic scattering.

Findings

High acceptance for positrons and hadrons

Effective particle identification including pions

Contributions to understanding nucleon spin structure

Abstract

The HERMES experiment is collecting data on inclusive and semi-inclusive deep inelastic scattering of polarised positrons from polarised targets of H, D, and He. These data give information on the spin structure of the nucleon. This paper describes the forward angle spectrometer built for this purpose. The spectrometer includes numerous tracking chambers (micro-strip gas chambers, drift and proportional chambers) in front of and behind a 1.3 T.m magnetic field, as well as an extensive set of detectors for particle identification (a lead-glass calorimeter, a pre-shower detector, a transition radiation detector, and a threshold Cherenkov detector). Two of the main features of the spectrometer are its good acceptance and identification of both positrons and hadrons, in particular pions. These characteristics, together with the purity of the targets, are allowing HERMES to make unique contributions to the understanding of how the spins of the quarks contribute to the spin of the nucleon.