Positron Transport System for Muonium-to-Antimuonium Conversion Experiment

TL;DR

The paper presents a positron transport system designed for the Muonium-to-Antimuonium Conversion Experiment, achieving high acceptance, precise position resolution, and effective background rejection through simulations.

Contribution

It introduces a novel positron transport system with optimized acceptance and timing for the MACE experiment, validated by detailed simulations.

Findings

Achieves 65.81% geometric acceptance for signal collection.

Provides a position resolution of approximately 88x102 micrometers.

Enables background rejection by a factor of 10^-7 using TOF-based methods.

Abstract

Muonium-to-Antimuonium Conversion Experiment (MACE) aims to find the charged lepton flavor violation (cLFV) process. A key component of MACE is the positron transport system (PTS) to collect and transport atomic positrons from antimuonium decays, which consists of an electrostatic accelerator and a solenoid beamline. Through field simulations in \textsc{COMSOL} and particle transport simulations based on \textsc{Geant4}, the PTS can achieve a geometric acceptance of the signal at 65.81(4)\% along with a position resolution of 88(1)~$\mu$m~$\times$~102(1)~$\mu$m. The system achieves 322.4(1)~ns transit time with a spread of 6.9(1)~ns, which allows for a TOF-based rejection of internal conversion backgrounds by a factor of $10^{-7}$. These promising results pave the way for new-physics signal identifications and background rejections in MACE and offer a novel paradigm for internal transport system in high-intensity frontiers.