The $S_{E1}$ factor of radiative $\alpha$ capture on $^{12}$C in cluster effective field theory

Abstract

The $S_{E1}$-factor of radiative $\alpha$-capture on $^{12}$C is studied in effective field theory up to next-to-leading order. A modification of the counting rules for the radiative capture amplitudes is discussed. We find that only two unfixed parameters remain in the amplitudes, and those two parameters are fitted to the experimental $S_{E1}$ data. An $S_{E1}$ factor is calculated at the Gamow-peak energy as $S_{E1}=59\pm 3$ keV$\cdot$b, and the result is found to be about 30% smaller than the estimates reported recently. An uncertainty of the estimate in the present work is also discussed.