J-PARCにおけるπ- p → K- X反応を用いたペンタクォークΘ+の探索

京都大学0048新制・課程博士博士(理学)甲第18673号理博第4022号新制||理||1580(附属図書館)31606京都大学大学院理学研究科物理学・宇宙物理学専攻(主査)教授 永江 知文, 教授 谷森 達, 准教授 成木 恵学位規則第4条第1項該当Doctor of ScienceKyoto UniversityDGA

Search for Muon-to-Electron Conversion with the COMET Experiment

Charged Lepton Flavor Violation is expected to be one of the most powerful tools to reveal physics beyond the Standard Model. The COMET experiment aims to search for the neutrinoless coherent transition of a muon into an electron in the field of a nucleus. Muon-to-electron conversion has never been observed, and can be, and would be, clear evidence of new physics if discovered. The experimental sensitivity of this process, defined as the ratio of the muon-to-electron conversion rate to the total muon capture rate, is expected to be significantly improved by a factor of 100 to 10,000 in the coming decade. The COMET experiment will take place at J-PARC with single event sensitivities of the orders of 10−15 and 10−17 in Phase-I and Phase-II, respectively. The ambitious goal of the COMET experiment is achieved by realizing a high-quality pulsed beam and an unprecedentedly powerful muon source together with an excellent detector apparatus that can tolerate a severe radiation environment. The construction of a new beam line, superconducting magnets, detectors and electronics is in progress towards the forthcoming Phase-I experiment. We present the experimental methods, sensitivity and backgrounds along with recent status and prospects

Development of a Cylindrical Drift Chamber for the COMET Phase-I Experiment

International audienceA search for $\mu$–e conversion, the COMET experiment, will be conducted at J-PARC. The experiment has two phases. Phase-I aims to measure the background directly and search for $\mu$–e conversion with a sensitivity of 10^−15. Phase-II will use the information gained in Phase-I and utilize a much more intense muon beam to achieve a sensitivity of 10^−17. The main detector of the COMET Phase-I experiment is a cylindrical drift chamber (CDC). The COMET CDC will be installed in a solenoidal magnetic field, surrounding the muon stopping targets. It was designed to efficiently detect signal electrons of $\mu$–e conversion (105 MeV/c) emitted from the targets with momentum resolution of 200 keV/c. The COMET CDC has already been constructed and the performance test using cosmic ray is in progress. The details of the CDC design and the analysis results of the cosmic ray test is reported

Radiation hardness study for the COMET Phase-I electronics

Radiation damage on front-end readout and trigger electronics is an important issue in the COMET Phase-I experiment at J-PARC, which plans to search for the neutrinoless transition of a muon to an electron. To produce an intense muon beam, a high-power proton beam impinges on a graphite target, resulting in a high-radiation environment. We require radiation tolerance to a total dose of 1.0kGy and 1MeV equivalent neutron fluence of 1.0×10 12 neq cm −2 including a safety factor of 5 over the duration of the physics measurement. The use of commercially-available electronics components which have high radiation tolerance, if such components can be secured, is desirable in such an environment. The radiation hardness of commercial electronic components has been evaluated in gamma-ray and neutron irradiation tests. As results of these tests, voltage regulators, ADCs, DACs, and several other components were found to have enough tolerance to both gamma-ray and neutron irradiation at the level we require. c.2019 Elsevier. B.V. All rights reserved

J-PARC E27 Experiment to Search for a K−pp Bound State

We have carried out an experimental search for the simplest kaonic nucleus, $K^{ - }pp$, by using the $d(\pi ^{ + },K^{ + })$ reaction at $p_{\pi ^{ + }}$ = 1.69 GeV/$c$. The differential cross section of this reaction with covering a wide missing-mass range from the $\Lambda$ production threshold to the $\Lambda (1405)/\Sigma (1385)$ region has been measured for the first time. The inclusive missing-mass shape of the $\Lambda$ and $\Sigma$ production region was understood with a simple quasi-free picture except for an enhancement at 2.13 GeV/$c^{2}$ due to a $\Sigma N$ cusp. An obtained peak attributed to $Y^{*}$ production was significantly shifted to the low mass side compared with the simulation by $- 22.4$ MeV/$c^{2}$