Quarkonium at the Frontiers of High Energy Physics: A Snowmass White Paper

In this Snowmass White Paper, we discuss physics opportunities involving heavy quarkonia at the intensity and energy frontiers of high energy physics. We focus primarily on two specific aspects of quarkonium physics for which significant advances can be expected from experiments at both frontiers. The first aspect is the spectroscopy of charmonium and bottomonium states above the open-heavy-flavor thresholds. Experiments at e^+ e^- colliders and at hadron colliders have discovered many new, unexpected quarkonium states in the last 10 years. Many of these states are surprisingly narrow, and some have electric charge. The observations of these charged quarkonium states are the first definitive discoveries of manifestly exotic hadrons. These results challenge our understanding of the QCD spectrum. The second aspect is the production of heavy quarkonium states with large transverse momentum. Experiments at the LHC are measuring quarkonium production with high statistics at unprecedented values of p_T. Recent theoretical developments may provide a rigorous theoretical framework for inclusive production of quarkonia at large p_T. Experiments at the energy frontier will provide definitive tests of this framework. Experiments at the intensity frontier also provide an opportunity to understand the exclusive production of quarkonium states.

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

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. The velocity expansion converges rapidly for approximate J/psi operator matrix elements.