Near-threshold top-pair excesses at the LHC are mostly ordinary higher-order QCD, not a free-standing toponium signal.

Summary. The paper constructs three public NLO+PS Monte Carlo generators (thr1, thr2, bb4l) that incorporate all-order Coulomb-enhanced threshold corrections (Sommerfeld factor plus bound-state poles) for ttbar production and decay near the 2mt threshold at the LHC. Using these tools the authors quantify, for the ATLAS bin (mtt < 350 GeV, p* < 50 GeV) and for coarser mtt cuts, the size of the enhancement beyond ordinary NLO/NNLO, the loosely defined bound-state contribution, and the residual impact of finite top width. They conclude that O(αs^{3}) already captures the bulk of the effect (~4 pb over baseline NLO), that the bound-state piece is a few pb, and that finite-width shifts remain at the 1–2 pb level once experimental resolution is coarser than Γt.

Significance. The work supplies concrete, publicly available generators that allow experimental analyses to include threshold resummation without double-counting NLO pieces and without treating toponium as an extra free-floating resonance. The order-by-order tables, the three-generator cross-check, the semi-analytic phase-space test (Fig. 7), and the comparison with an independent NLO-NRQCD calculation constitute a solid, falsifiable clarification of the ATLAS/CMS excess. The public codes and the explicit separation of double-top / single-top / no-top samples are particularly valuable for future LHC studies.