Parity-violating asymmetry inp→pscattering at medium energies

The longitudinal asymmetry in p→p scattering due to weak exchange of a charged pion is recalculated using a more realistic strong NN interaction to evaluate the effect of initial and final state rescattering. The pion-exchange contribution to the asymmetry at medium energy is smooth and equals 0.5×${10}^{\mathrm{-}7}$ at 800 MeV. This pion contribution has to be added to the conventional rho and omega contribution which, at this energy, has the same sign and about the same size. The total result, about 1.0×${10}^{\mathrm{-}7}$, should be compared to the experimental value at 800 MeV which is 2.4±1.1×${10}^{\mathrm{-}7}$.