Measurement Of The Muon Capture Rate In Hydrogen Gas And Determination Of The Proton'S Pseudoscalar Coupling G(P)

The rate of nuclear muon capture by the proton has been measured using a new technique based on a time projection chamber operating in ultraclean, deuterium-depleted hydrogen gas, which is key to avoiding uncertainties from muonic molecule formation. The capture rate from the hyperfine singlet ground state of the mu p atom was obtained from the difference between the mu(-) disappearance rate in hydrogen and the world average for the mu(+) decay rate, yielding Lambda(S)=725.0 +/- 17.4 s(-1), from which the induced pseudoscalar coupling of the nucleon, g(P)(q(2)=-0.88m(mu)(2))=7.3 +/- 1.1, is extracted.