Spin dependence of weak interaction in the process μ− + p → n + ν

Abstract Using the scintillation counter method measurement is made of the values, averaged with respect to two states of the hyperfine structure, of the a ¯ 0 asymmetry coefficients of (μ-e)-decay electrons in mesic atoms of silver, red and black phosphorus, and of the lifetime τ ¯ of mesons in these modifications of phosphorus. The quantities a ¯ 0 for red (insulator) and black (conductor) phosphorus directly indicate that the relaxation time of meson spins in mesic atoms decreases owing to the presence of conductivity electrons. On the basis of a ¯ 0 and τ ¯ are found the level populations n 1 and n 0 in the states F = 1 and F = 0 in phosphorus as well the probabilities λ 1 and λ 0 of the capture of mesons by the nucleus in these states. The values found directly indicate thatλ 1 ≠ λ 0 (weak interaction is spin-dependent) andλ 0 λ 1 (the capture from the state F = 0 occurs more rapidly than from the state F = 1). The lower limit of the magnitude Δλ/λ= (λ 1 −λ 0 )/(3/4λ 1 +1/4λ 0 ) obtained is direct evidence in favour of the (A-XV )-interaction.