Abstract
We study the dependence on the charm quark mass of the leading-order low-energy constants of the effective Hamiltonian, with the aim of elucidating the role of the charm mass scale in the rule for decay. To that purpose, finite-volume chiral perturbation theory predictions are matched to QCD simulations, performed in the quenched approximation with overlap fermions and . Light quark masses range between a few MeV up to around one third of the physical strange mass, while charm masses range between and a few hundred MeV. Novel variance reduction techniques are used to obtain a signal for penguin contractions in correlation functions involving four-fermion operators. The important role played by the subtractions required to construct renormalized amplitudes for is discussed in detail. We find evidence that the moderate enhancement of the amplitude previously found in the GIM limit increases only slightly as abandons the light quark regime. Hints of a stronger enhancement for even higher values of are also found, but their confirmation requires a better understanding of the subtraction terms.
- Received 24 June 2014
DOI:https://doi.org/10.1103/PhysRevD.90.094504
© 2014 American Physical Society