Development of the Range Counter for the COMET Phase-$α$ Experiment
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arXiv
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| Main Authors: | , , , , , , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866916874488381440 |
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| author | Oishi, Kou Aoki, Masaharu Kuribayashi, Shion Ueda, Shunya Ueno, Kazuki Chadeau, Nicolas Clouvel, Thomas Fujii, Yuki Fukao, Yoshinori Higashide, Masaaki Igarashi, Youichi Mihara, Satoshi Nishiguchi, Hajime Okabe, Kenya Uchida, Yoshi |
| author_facet | Oishi, Kou Aoki, Masaharu Kuribayashi, Shion Ueda, Shunya Ueno, Kazuki Chadeau, Nicolas Clouvel, Thomas Fujii, Yuki Fukao, Yoshinori Higashide, Masaaki Igarashi, Youichi Mihara, Satoshi Nishiguchi, Hajime Okabe, Kenya Uchida, Yoshi |
| contents | The COMET Phase-$α$ 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. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2505_07464 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Development of the Range Counter for the COMET Phase-$α$ Experiment Oishi, Kou Aoki, Masaharu Kuribayashi, Shion Ueda, Shunya Ueno, Kazuki Chadeau, Nicolas Clouvel, Thomas Fujii, Yuki Fukao, Yoshinori Higashide, Masaaki Igarashi, Youichi Mihara, Satoshi Nishiguchi, Hajime Okabe, Kenya Uchida, Yoshi Instrumentation and Detectors The COMET Phase-$α$ 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. |
| title | Development of the Range Counter for the COMET Phase-$α$ Experiment |
| topic | Instrumentation and Detectors |
| url | https://arxiv.org/abs/2505.07464 |