Chiral low-energy constants from tau data

TL;DR

This paper uses recent tau-decay data and QCD principles to precisely determine low-energy constants of chiral perturbation theory, improving understanding of fundamental hadronic interactions.

Contribution

It provides the most accurate values of certain chiral low-energy constants using tau decay data and QCD constraints, including the first phenomenological estimate of C_87.

Findings

Precise values of L_{9,10} at orders p^4 and p^6

First phenomenological determination of C_87

Enhanced understanding of low-energy QCD constants

Abstract

We analyze how the recent precise hadronic tau-decay data on the V-A spectral function and general properties of QCD such as analyticity, the operator product expansion and chiral perturbation theory (ChPT), can be used to improve the knowledge of some of the low-energy constants of ChPT. In particular we find the most precise values of L_{9,10} (or equivalently l_{5,6}) at order p^4 and p^6 and the first phenomenological determination of C_87 (c_50).