We employ an effective field theory (EFT) that exploits the separation of
scales in the p-wave halo nucleus 8B to describe the process
7Be(p,γ)8B up to a center-of-mass energy of 500 keV.
The calculation, for which we develop the lagrangian and power counting, is
carried out up to next-to-leading order (NLO) in the EFT expansion. The power
counting we adopt implies that Coulomb interactions must be included to all
orders in αem​. We do this via EFT Feynman diagrams computed in
time-ordered perturbation theory, and so recover existing quantum-mechanical
technology such as the two-potential formalism for the treatment of the
Coulomb-nuclear interference. Meanwhile the strong interactions and the E1
operator are dealt with via EFT expansions in powers of momenta, with a
breakdown scale set by the size of the 7Be core, Λ≈70 MeV.
Up to NLO the relevant physics in the different channels that enter the
radiative capture reaction is encoded in ten different EFT couplings. The
result is a model-independent parametrization for the reaction amplitude in the
energy regime of interest. To show the connection to previous results we fix
the EFT couplings using results from a number of potential model and
microscopic calculations in the literature. Each of these models corresponds to
a particular point in the space of EFTs. The EFT structure therefore provides a
very general way to quantify the model uncertainty in calculations of
7Be(p,γ)8B. We also demonstrate that the only
N2LO corrections in 7Be(p,γ)8B come from an
inelasticity that is practically of N3LO size in the energy range of
interest, and so the truncation error in our calculation is effectively
N3LO. We also discuss the relation of our extrapolated S(0) to the
previous standard evaluation.Comment: 68 pages, 10 figures, and 4 table