The lead-glass electromagnetic calorimeters for the magnetic spectrometers in Hall C at Jefferson Lab

TL;DR

This paper describes the design, construction, and performance of lead-glass electromagnetic calorimeters for Hall C spectrometers at Jefferson Lab, highlighting their energy resolution and particle separation capabilities based on experimental and simulated data.

Contribution

It provides detailed design considerations, construction information, and performance predictions for the calorimeters, including the new SHMS system, with comparison between simulation and experimental results.

Findings

Energy resolution better than 6%/√E for HMS and SOS

Pion/electron separation ratio of about 100:1 in 1-5 GeV range

Good agreement between simulated and experimental energy resolutions

Abstract

The electromagnetic calorimeters of the various magnetic spectrometers in Hall C at Jefferson Lab are presented. For the existing HMS and SOS spectrometers design considerations, relevant construction information, and comparisons of simulated and experimental results are included. The energy resolution of the HMS and SOS calorimeters is better than $\sigma/E \sim 6%/\sqrt E $, and pion/electron ($\pi/e$) separation of about 100:1 has been achieved in energy range 1 -- 5 GeV. Good agreement has been observed between the experimental and simulated energy resolutions, but simulations systematically exceed experimentally determined $\pi^-$ suppression factors by close to a factor of two. For the SHMS spectrometer presently under construction details on the design and accompanying GEANT4 simulation efforts are given. The anticipated performance of the new calorimeter is predicted over the full momentum range of the SHMS. Good electron/hadron separation is anticipated by combining the energy deposited in an initial (preshower) calorimeter layer with the total energy deposited in the calorimeter.