Average polarization of /sup 12/B in /sup 12/C( mu , nu ) /sup 12/B(g.s.) reaction: helicity of the pi -decay muon and nature of the weak coupling

The helicity, /b h//sup -/, of mu /sup -/ in pi -decay has been determined as positive (/b h//sup -/>or=+0.90) from the average polarization, /b P/ /sub av/ equiv , of /sup 12/B produced in the mu /sup -/+/sup 12 /C rarr nu /sub mu /+/sup 12/B reaction. Dynamical information is also on mu -capture: (i) the weak magnetism form factor, mu =4.5+/-1.1, and (ii) the sum of the induced pseudoscalar (/b g //sub P/) and the 2nd class induced tensor (/b g//sub T/) couplings versus /b g//sub A/, (/b g/ /sub P/+/b g//sub Gamma /)//b g//sub A /=7.1+/-2.7. The latter result, adopting the `canonical' value of /b g//sub P///b g//sub A/, leads to /b g//sub T ///b g//sub A/=+1+/-2/7 which is compatible with zero and in strong contradiction with the value sime -6 recently advocated by Kubodera, Delorme and Rho (see Phys. Rev. Lett., vol.38, p.312, (1977)).