Charm mass dependence of the weak hamiltonian in chiral perturbation theory
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# Charm mass dependence of the weak hamiltonian in chiral perturbation theory

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 Hernández Gamazo, Pilar; Laine, Mikko This document is a artículoDate2004 Este documento está disponible también en : http://hdl.handle.net/10550/43364 Suppose that the weak interaction Hamiltonian of four-flavour SU(4) chiral effective theory is known, for a small charm quark mass m_c. We study how the weak Hamiltonian changes as the charm quark mass increases, by integrating it out within chiral perturbation theory to obtain a three-flavour SU(3) chiral theory. We find that the ratio of the SU(3) low-energy constants which mediate Delta I=1/2 and Delta I=3/2 transitions, increases rather rapidly with m_c, as \sim m_c ln (1/m_c). The logarithmic effect originates from 'penguin-type' charm loops, and could represent one of the reasons for the Delta I=1/2 rule. Hernández Gamazo, Pilar Laine, Mikko 2004 Charm mass dependence of the weak hamiltonian in chiral perturbation theory Journal of High Energy Physics 2004 09 018-1 018-19 http://dx.doi.org/10.1088/1126-6708/2004/09/018

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