Thursday, June 20, 2013

1306.4445 (R. J. Crewther et al.)

Infrared Fixed Point in the Strong Running Coupling: Unraveling the
ΔI=1/2 puzzle in K-Decays
   [PDF]

R. J. Crewther, Lewis C. Tunstall
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 alpha_IR in the running coupling alpha_s 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 f_0(500) resonance and construct a chiral-scale perturbation theory CHPT_sigma for low-energy amplitudes expanded in alpha_s about alpha_IR. The Delta I = 1/2 rule emerges in the leading order of CHPT_sigma through a sigma-pole term K_S --> sigma --> 2 pi, with a K_S-sigma coupling fixed by data on 2 gamma --> 2 pi^0 and K_S --> 2 gamma. We also determine R_IR ~ 5 for the nonperturbative Drell-Yan ratio at alpha_IR.
View original: http://arxiv.org/abs/1306.4445

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