Towards High-Energy Factorization at Full NLO for Quarkonium Production

Abstract

Heavy-quarkonium hadroproduction at the LHC can access kinematic configurations in which the partonic center-of-mass energy is much larger than the quarkonium mass and transverse momentum. Fixed-order predictions may become unstable in this regime because large logarithms of the collision energy are not resummed. Extending high-energy factorization beyond leading logarithms requires process-dependent impact factors at next-to-leading order (NLO). We report the first complete NLO BFKL impact factors, with exact heavy-quark-mass dependence, for the production of the NRQCD states ${}^1S_0^{[1]}$, ${}^1S_0^{[8]}$, and ${}^3S_1^{[8]}$. The real-emission calculation is combined with the previously known virtual corrections through a local subtraction procedure. Soft singularities cancel, initial-state collinear poles are absorbed into the parton distributions, and rapidity divergences are removed by BFKL factorization. These results provide the ingredients needed for full-NLL studies of forward quarkonium and of quarkonium-associated production with a large rapidity separation.