Article Dans Une Revue Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment Année : 2026

Development of the Range Counter for the COMET Phase-$\alpha$ Experiment

Kou Oishi
  • Fonction : Auteur
Masaharu Aoki
  • Fonction : Auteur
Shion Kuribayashi
  • Fonction : Auteur
Shunya Ueda
  • Fonction : Auteur
Kazuki Ueno
  • Fonction : Auteur
Yuki Fujii
  • Fonction : Auteur
Yoshinori Fukao
  • Fonction : Auteur
Masaaki Higashide
  • Fonction : Auteur
Youichi Igarashi
  • Fonction : Auteur
Satoshi Mihara
  • Fonction : Auteur
Hajime Nishiguchi
  • Fonction : Auteur
Kenya Okabe
  • Fonction : Auteur
Yoshi Uchida
  • Fonction : Auteur

Résumé

The COMET Phase-$\alpha$ experiment aims to evaluate the novel muon transport beamline for the muon-to-electron conversion search at J-PARC, Japan. A dedicated Range Counter (RC) was developed to measure the momentum spectrum of transported negative muons with momenta of 30--100 MeV/$c$. The RC consists of graphite momentum degraders, a muon absorber, and plastic scintillation counters ($\rm T_0$, $\rm T_1$, and $\rm T_2$) to detect decay-in-orbit (DIO) electrons from stopped muons. The number of muons stopped in the absorber is reconstructed from the decay time distribution. A copper absorber was selected due to the short lifetime of muonic atoms in copper, which enhances signal separation. The counters' performance was evaluated experimentally. The $\rm T_0$ Counter, made of a $200\times 200\times 0.5~{\rm mm^3}$ scintillator plate, achieved a muon-trigger efficiency exceeding 99.9%. The $\rm T_1$ and $\rm T_2$ Counters also demonstrated high electron-detection efficiencies of $>99$%. Based on these results, simulation studies estimate the acceptance for reconstructing the number of DIO electrons from the absorber to be approximately 47% with a corresponding signal purity of 60% against muon capture-induced backgrounds.

Dates et versions

hal-05077658 , version 1 (21-05-2025)

Identifiants

Citer

Kou Oishi, Masaharu Aoki, Shion Kuribayashi, Shunya Ueda, Kazuki Ueno, et al.. Development of the Range Counter for the COMET Phase-$\alpha$ Experiment. Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2026, 1082, pp.170904. ⟨10.1016/j.nima.2025.170904⟩. ⟨hal-05077658⟩
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