Resonance Contribution to Radiative Neutron Capture on Lithium-7

We consider the contribution of the $3^+$ resonance state to low energy radiative neutron capture in a recently developed halo effective field theory. The resonance contribution is dominated by the M1 transition that proceeds through the initial $^5P_3$ state to the $2^+$ lithium-8 ground state. We present a model-independent calculation whose parameters are constrained by the known data on the $2^+$ ground state and the $3^+$ resonance state. This calculation~ extends the range of applicability of previous effective field theory calculations.