NEW EVALUATION OF THE PARITY VIOLATING PION-NUCLEON COUPLING

We evaluate the parity violating pion-nucleon coupling, Aπ, in the framework of the standard model of weak and electromagnetic interactions, including QCD corrections. We point out that important contributions to Aπ have been overlooked previously. Taking into account the uncertainties in the determination of the coefficients of the effective Hamiltonian, we find Aπ = (16-29) (Aπ)C, where (Aπ)C is the prediction of the Cabibbo theory, related to hyperon decay S-wave amplitudes. The sign of Aπ with respect to the strong pion-nucleon coupling is also determined. © 1979.