A new evaluation of the parity violating pion-nucleon coupling

Abstract We evaluate the parity violating pion-nucleon coupling, A π , in the framework of the standard model of weak and electromagnetic interactions, including QCD corrections. We point out that important contributions to A π have been overlooked previously. Taking into account the uncertainties in the determination of the coefficients of the effective Hamiltonian, we find A π = (16–29) ( A π ) C , where ( A π ) C is the prediction of the Cabibbo theory, related to hyperon decay S-wave amplitudes. The sign of A π with respect to the strong pion-nucleon coupling is also determined.