Radiative Neutron-Proton Capture in Effective Chiral Lagrangians

Abstract

We calculate the cross-section for the thermal $n+p\to d+\gamma$ process in chiral perturbation theory to next-to-next-to-leading order using heavy-fermion formalism. The exchange current correction is found to be $(4.5\pm 0.3)\%$ in amplitude and the chiral perturbation at one-loop order gives the cross section ${\sigma }_{th}^{np}=(334\pm 2)\text{mbox}mb$ which is in agreement with the experimental value $(334.2\pm 0.5)\text{mbox}mb$. Together with the axial charge transitions, this provides a strong support for the power of chiral Lagrangians for nuclear physics.

Comments: 9 pages, revtex, uses epsfig.sty, 2 uuencoded figures