Vector and axial-vector correlators in a nonlocal chiral quark model

Abstract

The behavior of nonperturbative parts of the isovector-vector and isovector and isosinglet axial-vector correlators at Euclidean momenta is studied in the framework of a covariant chiral quark model with nonlocal quark-quark interactions. The gauge covariance is ensured with the help of the P-exponents, with the corresponding modification of the quark-current interaction vertices taken into account. The low- and high-momentum behavior of the correlators is compared with the chiral perturbation theory and with the QCD operator product expansion, respectively. The V-A combination of the correlators obtained in the model reproduces quantitatively the ALEPH data on hadronic τdecays, transformed into the Euclidean domain via dispersion relations. The predictions for the electromagnetic π^\pm - π^0 mass difference and for the pion electric polarizability are also in agreement with the experimental values. The topological susceptibility of the vacuum is evaluated as a function of the momentum, and its first moment is predicted to be χ'(0)\approx (50 MeV)^2. In addition, the fulfillment of the Crewther theorem is demonstrated.