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Systematic effects of the quenched approximation on the strong penguin contribution to epsilon'/epsilon

C. Aubin, N. H. Christ, C. Dawson, J. Laiho, J. Noaki, S. Li, A. Soni

hep-latarXiv:hep-lat/0603025

Abstract

We discuss the implementation and properties of the quenched approximation in the calculation of the left-right, strong penguin contributions (i.e. Q6) to epsilon'/epsilon. The coefficient of the new chiral logarithm, discovered by Golterman and Pallante, which appears at leading order in quenched chiral perturbation theory is evaluated using both the method proposed by those authors and by an improved approach which is free of power divergent corrections. The result implies a large quenching artifact in the contribution of Q6 to epsilon'/epsilon. This failure of the quenched approximation affects only the strong penguin operators and so does not affect the Q8 contribution to epsilon'/epsilon nor Re A0, Re A2 and thus the Delta I=1/2 rule at tree level in chiral perturbation theory.

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