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Parity nonconserving observables in thermal neutron capture on a proton

We calculate parity nonconserving observables in the processes where a neutron is captured on a proton at the threshold energy radiating a photon. Various potential models such as Paris, Bonn and Argonne $v18$ are used for the strong interactions, and the meson-exchange description is employed for the weak interactions between hadrons. The photon polarization $P_γ$ in the unpolarized neutron capture process and photon asymmetry $A_γ$ in the polarized neutron capture process are obtained in terms of the weak meson-nucleon coupling constants. $A_γ$ turns out to be basically insensitive to the employed strong interaction models and thus can be uniquely determined in terms of the weak coupling constants, but $P_γ$ depends significantly on the strong interaction models.