THE DECAYS K+ -]E+NU-E-GAMMA AND K+-]MU+NU-MU-GAMMA, AND TENSORIAL COUPLINGS IN THE EFFECTIVE WEAK HAMILTONIAN

A tensorial coupling in the effective weak hamiltonian has been observed in a recent experiment on the decay pi- --> e- nu(e)GAMMABAR. The coupling constant for this interaction is about 10(6) times the one predicted by the standard model. If this effect really exists in the DELTAS = 0 effective weak hamiltonian, we suggest that an analogous kind of interaction may exist in the DELTAS = 1 sector. The decays K+ --> e+nu(e)gamma and K+ --> mu+nu(mu)gamma are reanalysed in the light of a possible tensorial coupling in the DELTAS = 1 effective hamiltonian. If this new effect exists also in the DELTAS = 1 sector, with the same coupling as in the AS= 0 sector, and if it is suppressed by the Cabibbo angle, then it can be easily observed at the DAPHNE laboratory in the mu decay of the K+. If this effect is not suppressed by the Cabibbo angle, then also the electron channel is very good for detecting it.