Speaker
Description
Proton-proton fusion (pp-fusion), in which two protons fuse to form a deuteron and emit a positron and neutrino, is a critical process in the life and death of stars and thus understanding it is essential for stellar simulations. However, due to the dominant Coulomb repulsion at energies much less than the nucleon mass like those found in the cores of stars, experimental measurements of the pp-fusion cross section are made difficult. Therefore, theoretical calculations with reliably quantified uncertainties are indispensable in quantifying those cross sections and corresponding reaction rates. Pursuant to this, low energy nuclear effective field theories (EFT's) have been employed to great success in calculating pp-fusion cross sections, though without reliable uncertainty estimates on the contributions from radiative corrections. Estimates on those contributions have been evaluated previously using the one-nucleon approximation, in which only the nucleon coupled to the weak current couples electromagnetically to the outgoing positron. In my talk I will discuss a recent calculation performed using pionless EFT in which we calculated the single-photon exchange contributions to pp-fusion, including, for the first time, explicit evaluation of the leading nuclear structure contributions due to radiative corrections. As time permits, I will also discuss progress on similar calculations for muon capture on the deuteron, in the frameworks of both pionless EFT and nonrelativistic QED.
