Renormalization of the tensor current in lattice QCD and the J /ψ tensor decay constant

Abstract

Lattice QCD calculations of form factors for rare Standard Model processes such as B→K+- use tensor currents that require renormalization. These renormalization factors, ZT, have typically been calculated within perturbation theory and the estimated uncertainties from missing higher order terms are significant. Here we study tensor current renormalization using lattice implementations of momentum-subtraction schemes. Such schemes are potentially more accurate but have systematic errors from nonperturbative artifacts. To determine and remove these condensate contributions we calculate the ground-state charmonium tensor decay constant, fJ/ψT, which is also of interest in beyond the Standard Model studies. We obtain fJ/ψT(MS¯,2 GeV)=0.3927(27) GeV, with ratio to the vector decay constant of 0.9569(52), significantly below 1. We also give ZT factors, converted to the MS¯ scheme, corrected for condensate contamination. This contamination reaches 1.5% at a renormalization scale of 2 GeV (in the preferred Regularisation Invariant Symmetric Momentum subtraction scheme) and so must be removed for accurate results.