A cylindrical drift chamber (CDC) has been constructed for the COMET Phase-I experiment where a lepton flavor violating process, the muon-to-electron conversion, is searched for with a sensitivity of 3-1015 at J-PARC. The CDC design was optimized to measure 105-MeV/c electrons as well as suppressing unwanted low-energy particles. In order to achieve required momentum resolution of 200 keV/c, the chamber is operated with a low-Z gas mixture of He (90%) and i-C4H10 (10%) to mitigate the multiple scattering effect. An alternated all stereo layer configuration is also adopted to enhance a good position resolution in the longitudinal direction. The 4,986 sense and 14,562 field wires were strung using gold-plated tungsten wires and unplated aluminum wires, respectively. Proper tensions were applied to control the wire gravitational sag within 55-7 mm for the sense wires, and the sag differences between a given sense wire and surrounding field wires within less than 100 mm. CDC performance tests using cosmic rays are successfully in progress. We have confirmed decent hit efficiency as well as spatial resolution of 170 mm including a tracking uncertainty.
|Proceedings of Science
|Published - 2019
|39th International Conference on High Energy Physics, ICHEP 2018 - Seoul, Korea, Republic of
Duration: Jul 4 2018 → Jul 11 2018
All Science Journal Classification (ASJC) codes