Ortho-Para Transition Rate in mu-Molecular Hydrogen and the Proton's Induced Pseudoscalar Coupling g~p

We report a measurement of the ortho-para transition rate in the p{mu}p molecule. The experiment was conducted at TRIUMF via the measurement of the time dependence of the 5.2 MeV neutrons from muon capture in liquid hydrogen. The measurement yielded an ortho-para rate {lambda}{sub op}=(11.1{+-}1.7{+-}(0.9/0.6))x10{sup 4} s{sup -1}, which is substantially larger than the earlier result of Bardin et al. The result has striking implications for the proton's induced pseudoscalar coupling g{sub p}, changing the value of g{sub p} obtained from the most precise ordinary muon capture measurement from 10.6{+-}2.7 to 0.8{+-}2.8, and from the sole radiative muon capture measurement from 12.2{+-}1.1 to 10.6{+-}1.2, bringing the latter result closer to theoretical predictions.