A strategy to study the role of the charm quark in explaining the Delta I=1/2 rule

Giusti L, Hernandez P, Laine M, Weisz P, Wittig H. A strategy to study the role of the charm quark in explaining the Delta I=1/2 rule. JOURNAL OF HIGH ENERGY PHYSICS. 2004;2004(11):016.We present a strategy designed to separate several possible origins of the well-known enhancement of the DeltaI - 1/2 amplitude in non-leptonic kaon decays. In particular, we seek to unambiguously quantify the role of the charm quark mass in the observed enhancement. This is achieved by considering QCD with an unphysically light charm quark, so that the theory possesses an approximate SU(4)(L) x SU(4)(R) chiral symmetry. The strategy proceeds by computing the relevant operator matrix elements and monitoring their values as the charm quark mass departs from the SU(4)-symmetric situation. We study the influence of the charm quark mass in Chiral Perturbation Theory. First results from lattice simulations in the SU(4)-symmetric limit are also discussed