Speaker
Description
We study bound-state effects in top-quark pair production close to threshold at the LHC, where sensitivity to non-relativistic dynamics has recently become accessible. Working within the non-relativistic QCD (NRQCD) framework, we assess the theoretical uncertainties affecting predictions for the top-quark pair invariant-mass distribution. We consider variations of the top-quark mass and width, the strong coupling, renormalization and factorization scales, as well as parton distribution functions. In addition, we provide a conservative estimate of uncertainties related to the limited accuracy of the color-singlet and color-octet Green's functions describing the formation of the quasi-bound top-quark pair state ("toponium"), which are computed using a Coulomb-like QCD potential. We compare these uncertainties with those of standard fixed-order QCD predictions at higher invariant masses and discuss implications for current and future ATLAS and CMS analyses.
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