Bayesian analysis of capture reactions $^3\\mathrm{He}(\\alpha,\\gamma)^7\\mathrm{Be}$ and $^3\\mathrm{H}(\\alpha,\\gamma)^7\\mathrm{Li}$

Abstract

Bayesian analysis of the radiative capture reactions $^3\\mathrm{He}(\\alpha,\\gamma)^7\\mathrm{Be}$ and $^3\\mathrm{H}(\\alpha,\\gamma)^7\\mathrm{Li}$ are performed to draw inferences about the cross sections at threshold. We do a model comparison of two competing effective field theory power countings for the capture reactions. The two power countings differ in the contribution of two-body electromagnetic currents. In one power counting, two-body currents contribute at leading order, and in the other they contribute at higher orders. The former is favored for $^3\\mathrm{He}(\\alpha,\\gamma)^7\\mathrm{Be}$ if elastic scattering data in the incoming channel is considered in the analysis. Without constraints from elastic scattering data, both the power countings are equally favored. For $^3\\mathrm{H}(\\alpha,\\gamma)^7\\mathrm{Li}$, the first power counting with two-body current contributions at leading order is favored with or without constraints from elastic scattering data.