Nuclear astrophysics and electron beams

Abstract. Electron beams provide important probes and constraints for nuclear astrophysics. This is especially exciting at energies within the regime of chiral effective field theory (EFT), which provides a systematic expansion for nuclear forces and electroweak operators based on quantum chromodynamics. This talk discusses some recent highlights and future directions based on chiral EFT, including nuclear structure and reactions for astrophysics, the neutron skin and constraints for the properties of neutron-rich matter in neutron stars and core-collapse supernovae, and the dark matter response of nuclei. CHIRAL EFFECTIVE FIELD THEORY Chiral EFT is based on the symmetries of quantum chromodynamics (QCD) and is applicable at momentum scales of the order of the pion mass Q ∼ mpi, where pions are included as explicit degrees of freedom and build up the long-range parts of strong interactions. In chiral EFT, nucleons interact via pion exchanges and shorter-range contact interactions [1, 2]. The resulting nuclear forces and consistent electroweak operators are organized in a systematic expansion in powers of Q/Λb, where Λb ∼ 500MeV denotes the breakdown scale, leading to a typical expansion parameter Q/Λb ∼ 1/3 for nuclei. As shown in Fig. 1, at a given order this includes contributions from one- or multi-pion exchanges and from contact interactions, with short-range couplings that are fit to data and thus capture all short-range effects relevant at low energies. The EFT enables one to estimate theoretical uncertainties and chiral EFT connects nuclear forces to the underlying theory through lattice QCD (see talk by W. Detmold) [3]