Violation of Quark-Hadron Duality and Spectral Chiral Moments in QCD

TL;DR

This paper investigates the spectral moments of the V-A correlation function in QCD, assessing quark-hadron duality violations using experimental tau decay data and statistical analysis to refine hadronic parameter estimates.

Contribution

It introduces a comprehensive method to evaluate duality violations in spectral moments, improving the accuracy of hadronic parameter extraction in QCD.

Findings

Accurate values for ChPT couplings L10 and C87.

Quantitative estimates of O6 and O8 contributions.

Duality-violation effects are often underestimated in prior studies.

Abstract

We analyze the spectral moments of the V-A two-point correlation function. Using all known short-distance constraints and the most recent experimental data from tau decays, we determine the lowest spectral moments, trying to assess the uncertainties associated with the so-called violations of quark-hadron duality. We have generated a large number of "acceptable" spectral functions, satisfying all conditions, and have used them to extract the wanted hadronic parameters through a careful statistical analysis. We obtain accurate values for the ChPT couplings L10 and C87, and a realistic determination of the dimension six and eight contributions in the operator product expansion, O6=(-5.4^{+3.6}_{-1.6})*10^-3 GeV^6 and O8=(-8.9^{+12.6}_{-7.4})*10^-3 GeV^8, showing that the duality-violation effects have been usually underestimated in previous literature.