Tritium β decay in pionless effective field theory

We calculate the β decay of tritium at next-to-leading order in pionless effective field theory. At this order, a low-energy parameter l1,A enters the calculation that is also relevant for a high-accuracy prediction of the solar proton-proton fusion rate. We use the tritium half-life to determine this parameter and provide uncertainty estimates. We show proper renormalization of our calculation analyzing the residual cutoff dependence of observables. We find that next-to-leading-order corrections contribute about 4% to the triton decay Gamow-Teller strength. We show that these conclusions are insensitive to different arrangements of the effective range expansion.