# Performance of the Muon $g-2$ calorimeter and readout systems measured with test beam data

## TL;DR

This paper reports on the testing and performance evaluation of the Muon $g-2$ calorimeter system at Fermilab, demonstrating it meets experimental requirements and informing reconstruction algorithms for the ongoing experiment.

## Contribution

It provides a comprehensive performance assessment of the calorimeter and readout systems, validating their readiness for the Muon $g-2$ experiment and guiding algorithm design.

## Key findings

- All subsystems meet or exceed performance requirements.
- Calorimeter response measurements informed reconstruction algorithm design.
- Complete installation of 24 calorimeter stations into the main experiment.

## Abstract

A single calorimeter station for the Muon $g-2$ experiment at Fermilab includes the following subsystems: a 54-element array of PbF$_{2}$ Cherenkov crystals read out by large-area SiPMs, bias and slow-control electronics, a suite of 800 MSPS waveform digitizers, a clock and control distribution network, a gain calibration and monitoring system, and a GPU-based frontend read out through a MIDAS data acquisition environment. The entire system performance was evaluated using 2.5 - 5 GeV electrons at the End Station Test Beam at SLAC. This paper includes a description of the individual subsystems and the results of measurements of the energy response and resolution, energy-scale stability, timing resolution, and spatial uniformity. All measured performances meet or exceed the $g-2$ experimental requirements. Based on the success of the tests, the complete production of the required 24 calorimeter stations has been made and installation into the main experiment is complete. Furthermore, the calorimeter response measurements determined here informed the design of the reconstruction algorithms that are now employed in the running $g-2$ experiment.