Radiative muon capture on carbon, oxygen, and calcium

Abstract

The photon energy spectra fro111 radiative xxluon captBle on C, 0, and Ca llave bee11 measured using a. time projection chamber as a pair spectrometer. The branching ratio for radiative muon capture is sensitive to g", the induced pseudoscalar coupling constant of the weak interaction, Expressed in terms of the axial-vector weak coupling constant g, values of g"/go = 5.7 6 0.8 and gJ, /g = 7.3 + 0.9 are obtained for Ca. and ' 0, respectively, from comparison with phenomenological calculations of the nuclear response. Froxxi comparison with microscopic calculations, values of g&/g~= 4.6 + 1.8, 13.6 +~s , and 16.2 +o'7 for Ca. , ' 0, and C, respectively, are obtained. The microscopic results are suggestive of a renormalization of the nucleonic form factors within the nucleus.

Induced pseudoscalar coupling of the proton weak interaction

“…However, like RMC on 40 Ca, due to the approximations in the calculations and the differences among the results of different calculations the case for g p /g a ∼ 6.7 in RMC on 16 O is not firmly established. There are also both theoretical and experimental results for 12 C. The most recent result, and the one with by far the smallest uncertainty is that of Armstrong et al (1991), R γ = 1.98 ± 0.20. This is to be compared with the sum rule result (Roig and Navarro , 1990) of R γ = 1.42, and the IA result, R γ = 3.60, and the MIA result, R γ = 1.48 (Gmitro et al, 1990).…”

“…There are also both theoretical and experimental results for 12 C. The most recent result, and the one with by far the smallest uncertainty is that of Armstrong et al (1991), R γ = 1.98 ± 0.20. This is to be compared with the sum rule result (Roig and Navarro , 1990) of R γ = 1.42, and the IA result, R γ = 3.60, and the MIA result, R γ = 1.48 (Gmitro et al, 1990).…”

Currents and Their Couplings in the Weak Sector of the Standard Model

“…In Table 7 we tabulate the branching ratio and g P values extracted from RMC measurements at PSI 175 and at TRIUMF 176,177 with various theories for the nuclear response functions. It is evident that the observed branching ratio is falling for heavier nuclei.…”