Charmonia decay constants from the QCD lattice and QCD sum rules

Abstract

Using lattice QCD and QCD sum rules we compute the lowest state charmonia JPC=0−+(ηc), 1−(J/ψ), and 1+−(hc) decay constants. For calculating the decay constant of J/ψ we use both the vector and tensor currents and compare the results. Lattice QCD results are obtained from the unquenched (Nf=2) simulations using twisted mass QCD at four lattice spacings and taking the continuum limit. In the QCD sum rule calculation we apply the moment sum rules. We also comment the phenomenological implications of calculated charmonia decay constants in ηc→γγ decay, and B→Xcc‾K decays.