| Radiative Muon Capture on Hydrogen and the Induced Pseudoscalar Coupling (2007) | |||||||||||||
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| The first measurement of the elementary process ¯ \Gamma p ! ¯ nfl is reported. A photon pair spectrometer was used to measure the partial branching ratio (2:10 \Sigma 0:22) \Theta 10 \Gamma8 for photons of k ? 60 MeV. The value of the weak pseudoscalar coupling constant determined from the partial branching ratio is g p (q 2 = \Gamma0:88m 2 ¯ ) = (9:8 \Sigma 0:7 \Sigma 0:3) \Delta g a (0), where the first error is the quadrature sum of statistical and systematic uncertainties and the second error is due to the uncertainty in op , the decay rate of the ortho to para p¯p molecule. This value of g p is ¸1.5 times the prediction of PCAC and pion-pole dominance. 23.40.-s, 13.10.+q, 23.40.Bw, 11.40.Ha Typeset using REVT E X (submitted to Physical Review Letters) In semi-leptonic weak interactions the strong force can, in general, induce four couplings in addition to the usual vector (g v ) and axial vector (g a ) couplings: weak magnetism (g m ), pseudoscalar (g p ), scalar (g ... | |||||||||||||
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