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Asymmetry in $\vec{n} + p -> d + γ$

Chang Ho Hyun·Tae-Sun Park·Dong-Pil Min
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Abstract

Heavy-baryon chiral perturbation theory (HBChPT) is applied to the asymmetry $A_γ$ in $\vec{n} + p \to d + γ$ 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 $v_{18}$ wavefunctions. In addition to the impulse contribution, both parity-conserving and parity-non-conserving two-body one-pion-exchange diagrams appear up to this order. Our prediction for the asymmetry is $A_γ= - 0.10 \hpiNN$, which is close to the Siegert's theorem based result, $A_γ\simeq -0.11 \hpiNN$. This illustrates that HBChPT is effective in the parity-non-conserving physics.

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Chang Ho Hyun, Tae-Sun Park, Dong-Pil Min. 2001-07-23. Asymmetry in $\vec{n} + p -> d + γ$. https://doi.org/10.1016/s0370-2693(01)00917-0

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