Imaginary-time method for the radiative capture reaction rate

We propose a new computational method for astrophysical reaction rate of the radiative capture process. In the method, an evolution of a wave function is calculated along the imaginary-time axis, which is identified as the inverse temperature. It enables direct evaluation of reaction rate as a function of temperature without solving any scattering problem. The method is tested for two-body radiative capture reaction, O-16(alpha, gamma)Ne-20, showing that it gives identical results to those calculated by the ordinary procedure. This method will be suited for calculation of triple-alpha radiative capture rate, for which an explicit construction of the scattering solution is difficult.