Asymmetry in (n)over-right-arrow+p→d+γ

Heavy-baryon chiral perturbation theory (HBChPT) is applied to the asymmetry A gamma in (n) over right arrow + p --> d + gamma at threshold, which arises due to the weak parity non-conserving interactions. Instead of appealing to Siegert's theorem, transition operators up to next-to-leading chiral order are derived and the corresponding amplitudes are evaluated with the Argonne nu (18) wavefunctions. In addition to the impulse contribution, both parity-conserving and parity-non-conserving two-body one-pion-exchange diagrams A gamma = -0.10h(pi NN)(,)((1)) which is close to the Siegert's theorem based appear up to this order. Our prediction for the asymmetry is A gamma = -0.10h(pi NN)((1)),which is too close to the Siegert's theorem based result, A gamma similar or equal to -0.11h(pi NN)(.)((1)) This illustrates that HBChPT is effectively applied to the parity-non-conserving physics. (C) 2001 Elsevier Science B.V. All rights reserved.