QCD coupling which respects lattice restrictions at low energies

by Cesar Ayala (Valencia)

Friday Feb 10, 2017, 2:30 PM → 3:30 PM Europe/Madrid

IFAE Seminar room (IFAE)

Newer large volume lattice calculations for gluon and ghost dressing functions strongly indicate that the QCD running coupling, in a specific scheme, goes to zero at low spacelike momenta. We construct such a QCD coupling which fulfills also various other physically motivated conditions. At high momenta it becomes the underlying perturbative coupling to a very high precision. And at intermediate low squared momenta it reproduce correctly the nonstrange semihadronic decay rate of tau lepton. The coupling is constructed in such a way that it reflects qualitatively correctly the holomorphic (analytic) behavior of spacelike observables in the complex plane of the squared momenta, as dictated by the general principles of QFT. Application of the Borel sum rules to tau decay V+A spectral functions allows us to obtain values for the gluon (dimension-4) condensate and the dimension-6 condensate, which reproduce the measured OPAL and ALEPH data to a significantly better precision than the perturbative MSbar coupling approach.