Effect of the N3LO three-nucleon contact interaction on p−d scattering observables

Abstract

Chiral effective field theory allows one to express nuclear physics observables in terms of low-energy constants (LECs), representing physics at unresolved scales. In this work the authors focus on the two-nucleon contact interaction at fourth order (N3LO) and use a unitary transformation to reduce the number of involved LECs. This procedure induces a three-nucleon ($3N$) interaction depending on five unconstrained LECs. Those can be used, in association with a two-nucleon ($2N$) interaction, to fit very accurate data on polarization observables at low energies, in particular the $p$-$d$ ${A}_{y}$ polarization asymmetry. Thereby, adjusting the induced $3N$ N3LO LECs can solve the long-standing ${A}_{y}$ puzzle.