Infrared Fixed Point in the Strong Running Coupling: Unraveling the I=1/2 puzzle in K-Decays
Abstract
In this talk, we present an explanation for the Delta I = 1/2 rule in K-decays based on the premise of an infrared fixed point alphaIR in the running coupling alphas of quantum chromodynamics (QCD) for three light quarks u,d,s. At the fixed point, the quark condensate spontaneously breaks scale and chiral SU(3)L x SU(3)R symmetry. Consequently, the low-lying spectrum contains nine Nambu-Goldstone bosons: pi,K,eta and a QCD dilaton sigma. We identify sigma as the f0(500) resonance and construct a chiral-scale perturbation theory CHPTsigma for low-energy amplitudes expanded in alphas about alphaIR. The Delta I = 1/2 rule emerges in the leading order of CHPTsigma through a sigma-pole term KS --> sigma --> 2 pi, with a KS-sigma coupling fixed by data on 2 gamma --> 2 pi0 and KS --> 2 gamma. We also determine RIR ~ 5 for the nonperturbative Drell-Yan ratio at alphaIR.