Absorption ofμ−Mesons inC12

Abstract

It is known that there is a strong similarity between the electron-nucleon and electron-muon weak interactions. This paper is a report on an experimental investigation of the third leg of the triangle, the muon-nucleon interaction. The absorption of negative cosmic-ray muons stopped in ${\mathrm{C}}^{12}$ was studied, and the probability per second of absorption resulting in the formation of ${\mathrm{B}}^{12}$ in the ground state was measured and found to be 9050±950 ${\sec }^{-1\mathrm{}}$. This is compared to the known rate of $\beta$ decay of ${\mathrm{B}}^{12}$ to the ground state of ${\mathrm{C}}^{12}$, 33.2±0.65 ${\sec }^{-1\mathrm{}}$. The ratio of the rates is 273±29. In the allowed approximation, the nuclear matrix elements for the two processes are the same, and the ratio of the rates can be calculated in terms of the ratio of the coupling constants without assuming a nuclear model. The short wavelength of the neutrino emitted in $\mu$ absorption (13 fermis) causes forbidden matrix elements to make an important contribution to the $\mu$-absorption rate, so that the theoretical prediction is dependent on the nuclear model. Within the uncertainties of the calculation, the electron-nucleon and muon-nucleon axial vector coupling constants are the same.