Design of a CsI(Tl) Calorimeter for Muonium-to-Antimuonium Conversion Experiment

TL;DR

This paper presents the design and simulation of a near-4π calorimeter for the MACE experiment, aiming to detect muonium-to-antimuonium conversion with high efficiency and resolution, significantly improving sensitivity over previous experiments.

Contribution

It introduces a novel calorimeter design optimized for MACE, with detailed Monte Carlo simulations for geometry, background, and performance validation.

Findings

Energy resolution of 10.8% at 511 keV

Signal efficiency of 78.3% for gamma-ray events

Effective background estimation and detector validation

Abstract

The Muonium-to-Antimuonium Conversion Experiment (MACE) is proposed to search for charged lepton flavor violation and increase the sensitivity by more than two orders of magnitude compared to the MACS experiment at PSI in 1999. A clear signature of this conversion is the positron produced from antimuonium decay. This paper presents a near-$4\pi$-coverage calorimeter designed for MACE, which can provide an energy resolution of 10.8% at 511 keV, and a signal efficiency of 78.3% for annihilation $\gamma$-ray events. Detailed Monte-Carlo simulations using MACE offline software based on Geant4 are performed for geometry optimization, coincidence system design, background estimation, and benchmark detector validation.