Minimally non-local nucleon-nucleon potentials with chiral two-pion exchange including $\Delta$'s

TL;DR

This paper develops a coordinate-space chiral nucleon-nucleon potential including ${ ext{Delta}}$-isobar states in two-pion exchange, fitted to extensive scattering data, achieving a good fit with $$/datum around 1.3.

Contribution

It introduces a new chiral potential with ${ ext{Delta}}$ intermediate states and rearranged contact terms, fitted to a large database of nucleon scattering data.

Findings

Achieves $$/datum of about 1.3 for the fit.

Provides a set of models with different cutoff parameters.

Includes ${ ext{Delta}}$-isobar effects in the potential.

Abstract

We construct a coordinate-space chiral potential, including $\Delta$-isobar intermediate states in its two-pion-exchange component. The contact interactions entering at next-to-leading and next-to-next-to-next-to-leading orders ($Q^2$ and $Q^4$, respectively, $Q$ denoting generically the low momentum scale) are rearranged by Fierz transformations to yield terms at most quadratic in the relative momentum operator of the two nucleons. The low-energy constants multiplying these contact interactions are fitted to the 2013 Granada database, consisting of 2309 $pp$ and 2982 $np$ data (including, respectively, 148 and 218 normalizations) in the laboratory-energy range 0--300 MeV. For the total 5291 $pp$ and $np$ data in this range, we obtain a $\chi^2$/datum of roughly 1.3 for a set of three models characterized by long- and short-range cutoffs, $R_{\rm L}$ and $R_{\rm S}$ respectively, ranging from $(R_{\rm L},R_{\rm S})=(1.2,0.8)$ fm down to $(0.8,0.6)$ fm. The long-range (short-range) cutoff regularizes the one- and two-pion exchange (contact) part of the potential.