Neutral currents in thermal np capture

We present a calculation of the circular polarization P_γ and asymmetry A_γ of gamma radiation in thermal neutron-proton capture with a tested numerical accuracy of 1%. The effect of neutral currents is discussed on the example of the Weinberg-Salam model of weak interaction. It is also shown that a one percent contribution of the ³S₁ scattering state to the regular np capture cross section destroys the favourable isospin selection rule in the polarization.