The s-wave pion-nucleus optical potential

TL;DR

This paper develops a unitarized chiral model to calculate the s-wave pion-nucleus optical potential, incorporating multiple rescattering, Pauli blocking, and higher order corrections, aligning with empirical data.

Contribution

It introduces a comprehensive unitarized chiral approach for the s-wave pion-nucleus optical potential, including isoscalar and isovector components with improved theoretical uncertainty analysis.

Findings

The model can reproduce the repulsive potential seen in phenomenology.

An enhancement of the isovector part aligns with empirical data.

Theoretical uncertainties are larger than previously estimated.

Abstract

We calculate the s-wave part of the pion-nucleus optical potential using a unitarized chiral approach that has been previously used to simultaneously describe pionic hydrogen and deuterium data as well as low energy pi N scattering in the vacuum. This energy dependent model allows for additional isoscalar parts in the potential from multiple rescattering. We consider Pauli blocking and pion polarization in an asymmetric nuclear matter environment. Also, higher order corrections of the pi N amplitude are included. The model can accommodate the repulsion required by phenomenological fits, though the theoretical uncertainties are bigger than previously thought. At the same time, we also find an enhancement of the isovector part compatible with empirical determinations.