Determine short-distance isospin-breaking contact-term low-energy constants

Determine the low-energy constants of the short-distance contact potential that absorbs the ultraviolet divergence of the long-distance isospin-breaking potential, thereby reducing the associated theoretical uncertainty in the neutrinoless double-beta-decay rate.

Background

The paper discusses the ultraviolet structure of isospin-breaking nuclear potentials by analogy with the long-distance potential appearing in neutrinoless double-beta decay. A long-distance potential can possess an ultraviolet divergence that must be absorbed into a short-distance contact interaction. The corresponding short-distance isospin-breaking potential is parameterized by two nucleus-independent low-energy constants, a_1 and a_2, in the T=1 and T=2 channels.

These constants are not presently known and introduce a substantial theoretical uncertainty into predictions of the neutrinoless double-beta-decay rate. The paper later suggests determining them by fitting the IMME coefficients b and c in a nuclear isotriplet and testing the resulting values against other isotriplets and isospin-breaking two-nucleon scattering-length combinations.