Charm mass dependence of the weak Hamiltonian in chiral perturbation theory

P Hernandez, M Laine
2004 Journal of High Energy Physics  
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
more » ... /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.
doi:10.1088/1126-6708/2004/09/018 fatcat:hzop5sr225ef7gtfsb3aho5jzy