Construction and Basic Performance Evaluation of the Straw Tube Tracker for the COMET Experiment

Authors

Masaaki Higashide¹^,*, Kazuki Ueno², Naoya Kamei³, Junichi Suzuki³, Hajime Nishiguchi³, Eitaro Hamada³, Satoshi Mihara³, and the COMET Collaboration

Affiliations

¹Department of Particle and Nuclear Physics, SOKENDAI, Tsukuba, Ibaraki 305-0801, Japan

²Department of Physics, Osaka University, Toyonaka, Osaka 560-0043, Japan

³Institute of Particle and Nuclear Studies, KEK, Tsukuba, Ibaraki 305-0801, Japan

Journal

Published Date

6/12/26

DOI

Abstract

The COMET experiment at J-PARC aims to search for the muon-to-electron conversion in aluminum, a charged lepton flavor violation process predicted by theories beyond the standard model with a branching ratio of up to 10⁻¹⁵. It employs a detector called the straw tube tracker to measure electron momentum with a resolution better than 200 keV/c. The straw tube tracker consists of five stations, each comprising 480 straw tubes with ultra-thin cathode. This low-mass design tracker will be operated in a vacuum during the COMET experiment, enabling strong suppression of Coulomb multiple scattering and achieving high momentum resolution. The first station of the straw tube tracker has been constructed, and beam irradiation to the first station by the COMET beamline has been conducted. Performance evaluation is ongoing, and it has been confirmed that the first station’s gain meets the required specifications.