Constraint on the light quark mass mq from QCD sum rules in the I=0 scalar channel
AbstractIn this paper, we reanalyze the I=0 scalar channel with the improved Monte-Carlo-based QCD sum rules, which combines the rigorous Hölder-inequality-determined sum rule window and a parametrization with two-Breit-Wigner-type resonances for the phenomenological spectral density that satisfies the low-energy theorem for the scalar form factor. Considering the uncertainties of the QCD parameters and the experimental masses and widths of the scalar resonances σ and f0(980), we obtain a prediction for light quark mass mq(2 GeV)=12(mu(2 GeV)+md(2 GeV))=4.7-0.7+0.8 MeV, which is consistent with the Particle Data Group value and QCD sum rule determinations in the pseudoscalar channel. This agreement provides a consistent framework connecting QCD sum rules and low-energy hadronic physics. We also obtain the decay constants of σ and f0(980) at 2 GeV, which are approximately 0.64–0.83 and 0.40–0.48 GeV, respectively.