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Towards a determination of the chiral couplings at NLO in 1/N(C): L8(mu) and C38(mu)

I. Rosell, J. J. Sanz-Cillero, A. Pich

hep-pharXiv:hep-ph/0610290

Abstract

We present a dispersive method which allows to investigate the low-energy couplings of chiral perturbation theory at the next-to-leading order (NLO) in the 1/N(C) expansion, keeping full control of their renormalization scale dependence. Using the resonance chiral theory Lagrangian, we perform a NLO calculation of the scalar and pseudoscalar two-point functions, within the single-resonance approximation. Imposing the correct QCD short-distance constraints, one determines their difference Pi(t)=PiS(t)-PiP(t) in terms of the pion decay constant and resonance masses. Its low momentum expansion fixes then the low-energy chiral couplings L8 and C38. At mu0=0.77 GeV, we obtain L8(mu0)SU(3) = (0.6+-0.4)10-3 and C38(mu0)SU(3)=(2+-6)10-6.

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