ChPT parameters from tau-decay data

TL;DR

This paper uses tau-decay data to precisely determine QCD chiral symmetry breaking parameters, including effective couplings and operator contributions, by analyzing spectral functions and accounting for duality violations.

Contribution

It introduces a resonance-based parametrization with short-distance constraints to accurately extract chiral parameters from tau-decay spectral data.

Findings

Accurate values for L10 and C87 obtained.

Quantification of dimension-six and -eight operator contributions.

Estimation of uncertainties from quark-hadron duality violations.

Abstract

Using the updated ALEPH V-A spectral function from tau decays, we determine the lowest spectral moments of the left-right correlator and extract dynamical information on order parameters of the QCD chiral symmetry breaking. Uncertainties associated with violations of quark-hadron duality are estimated from the data, imposing all known short-distance constraints on a resonance-based parametrization. Employing proper pinched weight functions, we obtain an accurate determination of the effective chiral couplings L10 and C87 and the dimension-six and -eight contributions in the Operator Product Expansion.