# Measurement of the energy and time resolution of a undoped CsI + MPPC array for the Mu2e experiment

## TL;DR

This study measures the energy and time resolution of an undoped CsI crystal array coupled with MPPCs, demonstrating a 16.4% energy resolution at 100 MeV and a 110 ps time resolution, relevant for the Mu2e experiment.

## Contribution

First detailed measurement of energy and time resolution of undoped CsI + MPPC array for Mu2e, using electron beam tests in the 80-120 MeV range.

## Key findings

- Energy resolution of 16.4% at 100 MeV
- Time resolution of about 110 ps at 100 MeV
- Measurements performed with electron beam at Frascati

## Abstract

This paper describes the measurements of energy and time response and resolution of a 3 x 3 array made of undoped CsI crystals coupled to large area Hamamatsu Multi Pixel Photon Counters. The measurements have been performed using the electron beam of the Beam Test Facility in Frascati (Rome, Italy) in the energy range 80-120 MeV. The measured energy resolution, estimated with the FWHM, at 100 MeV is 16.4%. This resolution is dominated by the energy leakage due to the small dimensions of the prototype. The time is reconstructed by fitting the leading edge of the digitized signals and applying a digital constant fraction discrimination technique. A time resolution of about 110 ps at 100 MeV is achieved.