The Pion Sum Rule beyond the Chiral Limit
High Energy Physics - Phenomenology
2026-02-06 v1
Abstract
The difference between the charged and neutral pion masses can be predicted from a well-known dispersion relation involving an infinite-energy integral over experimental data, the pion sum rule. This relation, however, holds only in the chiral limit. Here we combine several nonperturbative techniques to determine the form of the physical finite-energy integral, thereby generalizing this sum rule to include effects linear in the light-quark masses. We test the dispersion relation using hadronic tau-decay data.
Cite
@article{arxiv.2602.05672,
title = {The Pion Sum Rule beyond the Chiral Limit},
author = {Johan Bijnens and Nils Hermansson-Truedsson and Antonio Rodríguez-Sánchez},
journal= {arXiv preprint arXiv:2602.05672},
year = {2026}
}
Comments
22 pages, 6 figures