Precision Measurement of Nuclear Muon Capture by 3He

Abstract

The muon capture rate in the reaction µ − + 3 He → ν µ + 3 H has been measured at PSI using a modular high pressure ionization chamber. The rate corresponding to statistical hyperfine population of the µ 3 He atom is (1496.0±4.0) s −1 . This result confirms the PCAC prediction for the pseudoscalar form factors of the 3 He -3 H system and the nucleon. PACS: 23.40.-s * This paper is part of the thesis works of W. Prymas and N.I. Voropaev

A circulating hydrogen ultra-high purification system for the MuCap experiment

“…Thus, the impurity concentration in the TPC detector is defined by the ratio of outgassing flow and circulation flow. Initially a circulation system consisting of a mechanical pump and a palladium (Pd) filter was considered [1]. High vacuum rated pumps that operate at 10 bar pressure are not commercially available, and Pd filters supporting the required flux of 3 slpm are expensive.…”

“…The MuCap experiment [1,2] measures the rate L S for the basic electroweak process of nuclear muon capture on the proton, µp → n + ν µ , from the singlet hyperfine state of the muonic hydrogen atom. A measurement of L S with 1% precision determines the least well-known of the nucleon charged current form factors, the induced pseudoscalar form factor g P , to 7%.…”