title: Proton-proton weak capture in chiral effective field theory.
abstract: The astrophysical S factor for proton-proton weak capture is calculated in chiral effective field theory over the center-of-mass relative-energy range 0-100 keV. The chiral two-nucleon potential derived up to next-to-next-to-next-to leading order is augmented by the full electromagnetic interaction including, beyond Coulomb, two-photon and vacuum-polarization corrections. The low-energy constants entering the weak current operators are fixed so as to reproduce the A=3 binding energies and magnetic moments and the Gamow-Teller matrix element in tritium β decay. Contributions from S and P partial waves in the incoming two-proton channel are retained. The S factor at zero energy is found to be S(0)=(4.030±0.006)×10(-23) MeV fm(2), with a P-wave contribution of 0.020×10(-23) MeV fm(2). The theoretical uncertainty is due to the fitting procedure of the low-energy constants and to the cutoff dependence.
authors.affiliation: Department of Physics, University of Pisa, 56127 Pisa, Italy and INFN-Pisa, 56127 Pisa, Italy.
authors.forename: L E
authors.initials: LE
authors.lastname: Marcucci
authors.forename: R
authors.initials: R
authors.lastname: Schiavilla
authors.forename: M
authors.initials: M
authors.lastname: Viviani