Determination of SU(2) Chiral Perturbation Theory low energy constants from a precise description of pion-pion scattering threshold parameters

TL;DR

This paper precisely determines the low energy constants in SU(2) Chiral Perturbation Theory for pion-pion scattering using sum rules and scattering data, highlighting the need for higher order contributions.

Contribution

It provides a new set of sum rules for third order coefficients and refines the values of low energy constants with high precision.

Findings

Results align with previous determinations using scattering lengths and slopes.

Higher order contributions are necessary to match third order coefficients.

Sum rules up to third order improve understanding of pion-pion interactions.

Abstract

We determine the values of the one- and two-loop low energy constants appearing in the SU(2) Chiral Perturbation Theory calculation of pion-pion scattering. For this we use a recent and precise sum rule determination of some scattering lengths and slopes that appear in the effective range expansion. In addition we provide sum rules for these coefficients up to third order in the expansion. Our results when using only the scattering lengths and slopes of the S, P, D and F waves are consistent with previous determinations, but seem to require higher order contributions if they are to accommodate the third order coefficients of the effective range expansion.