Colour structure in threshold resummation and squark-antisquark production at NLL

TL;DR

The paper develops a framework for resumming soft and Coulomb gluon effects in heavy colored-particle pair production, introducing a color-space basis that diagonalizes the soft function and deriving the two-loop soft anomalous dimension for NNLL accuracy. It then provides a momentum-space resummation formula that combines NLL soft-gluon corrections with Coulomb resummation, applied to squark-antisquark production at the LHC. Matching to fixed-order NLO and comparison with NNLO approximate results illustrate sizable threshold and Coulomb enhancements and improved scale stability. The work advances precise predictions for heavy particle production near threshold, with direct implications for SUSY searches at the LHC.

Abstract

We consider the resummation of soft and Coulomb gluons for pair-production processes of heavy coloured particles at hadron colliders, and discuss recent results on the construction of a basis in colour space that diagonalizes the soft function to all orders in perturbation theory and the determination of the two-loop soft anomalous dimension needed for NNLL resummations. We present results for the combined NLL resummation of soft gluon and Coulomb-gluon effects for squark-antisquark production at the LHC.