Construction and Performance of the Barrel Electromagnetic Calorimeter for the GlueX Experiment

TL;DR

This paper details the design, calibration, and operational performance of the barrel electromagnetic calorimeter used in the GlueX experiment at Jefferson Lab, highlighting its unique geometry and effective detection capabilities for photon-induced particles.

Contribution

It presents the construction, calibration, and performance evaluation of a novel lead-scintillating fiber calorimeter with silicon photomultiplier readout for the GlueX experiment.

Findings

Calorimeter performs as expected for electromagnetic showers below 2.5 GeV.

Energy resolution characterized as 5.2%/√E + 3.6%.

Timing resolution of 150 ps at 1 GeV.

Abstract

The barrel calorimeter is part of the new spectrometer installed in Hall D at Jefferson Lab for the GlueX experiment. The calorimeter was installed in 2013, commissioned in 2014 and has been operating routinely since early 2015. The detector configuration, associated Monte Carlo simulations, calibration and operational performance are described herein. The calorimeter records the time and energy deposited by charged and neutral particles created by a multi-GeV photon beam. It is constructed as a lead and scintillating-fiber calorimeter and read out with 3840 large-area silicon photomultiplier arrays. Particles impinge on the detector over a wide range of angles, from normal incidence at 90 degrees down to 11.5 degrees, which defines a geometry that is fairly unique among calorimeters. The response of the calorimeter has been measured during a running experiment and performs as expected for electromagnetic showers below 2.5 GeV. We characterize the performance of the BCAL using the energy resolution integrated over typical angular distributions for $\pi^0$ and $\eta$ production of $\sigma_E/E$=5.2\%/$\sqrt{E(\rm{GeV})} \oplus$ 3.6\% and a timing resolution of $\sigma$\,=\,150\,ps at 1\,GeV.