The ⁰ -> decay width is analyzed within the combined framework of Chiral Perturbation Theory and the 1/N_c expansion up to order(p⁶) and order(p⁴ x 1/N_c) in the decay amplitude. The ' is explicitly included in the analysis. It is found that the decay width is enhanced by about 4% due to the isospin-breaking induced mixing of the pure U(3) states. This effect, which is of leading order in the low energy expansion, is shown to persist nearly unchanged at next to leading order. The chief prediction Gamma_pi0_-> = 8.10 eV is estimated to have an uncertainty of less than 1%. Observations on the and ' can also be made, especially about their mixing, which is shown to be significantly affected by next to leading order corrections.

Authors: J.L. Goity, A.M. Bernstein, J.F. Donoghue, B.R. Holstein

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