Order-alpha_s corrections to the quarkonium electromagnetic current at all orders in the heavy-quark velocity

Understand

We compute in order alpha_s the nonrelativistic QCD (NRQCD) short-distance coefficients that match quark-antiquark operators of all orders in the heavy-quark velocity v to the electromagnetic current.

• We employ a new method to compute the one-loop NRQCD contribution to the matching condition.
• The new method uses full-QCD expressions as a starting point to obtain the NRQCD contribution, thus greatly streamlining the calculation.
• Our results show that, under a mild constraint on the NRQCD operator matrix elements, the NRQCD velocity expansion for the quark-antiquark-operator contributions to the electromagnetic current converges.