Lawrence Berkeley National Laboratory
A Measurement of the Rate of Muon Capture in Hydrogen Gas and Determination of the Proton's
Induced Pseudoscalar Coupling gP
- Author(s): Banks, Thomas Ira
- et al.
This dissertation describes a measurement of the rate of nuclear muon capture by the proton, performed by the MuCap Collaboration using a new technique based on a time projection chamber operating in ultraclean, deuterium-depleted hydrogen gas at room temperature and 1 MPa pressure. The hydrogen target's low gas density of 1 percent compared to liquid hydrogen is key to avoiding uncertainties that arise from the formation of muonic molecules. The capture rate was obtained from the difference between the mu- disappearance rate in hydrogen--as determined from data collected in the experiment's first physics run in fall 2004--and the world average for the mu+ decay rate. After combining the results of my analysis with the results from another independent analysis of the 2004 data, the muon capture rate from the hyperfine singlet ground state of the mu-p atom is found to be Lambda_S = 725.0 +- 17.4 1/s, from which the induced pseudoscalar coupling of the nucleon, gP(q2 = -0.88 m2mu)= 7.3 +- 1.1, is extracted. This result for gP is consistent with theoretical predictions that are based on the approximate chiral symmetry of QCD.