eta-eta ' mixing and the next-to-leading-order power correction

Abstract

The next-to-leading-order O(1/Q(4)) power corrections for etagamma and eta(')gamma form factors are evaluated and employed to explore the eta-eta(') mixing. The parameters of the two-mixing-angle scheme are extracted from the data for form factors, two-photon decay widths, and radiative J/psi decays. The chi(2) analysis gives the result f(eta1)=(1.16+/-0.06)f(pi),f(eta8)=(1.33+/-0.23)f(pi),theta(1)=-9degrees+/-3degrees,theta(8)=-21.3degrees+/-2.3degrees, where f(eta1(8)) and theta(1(8)) are the decay constants and the mixing angles for the singlet (octet) state. In addition, we arrive at a stringent range for f(eta)('c):-10 MeVless than or equal tof(eta)('c)less than or equal to-4 MeV.