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arXiv · 2610.15493

Probing the chromo-electric dipole moment of top quark near the toponium production threshold at LHC

Kai Ma·Tong Li
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Abstract

The recent observation of an excess near the kinematic $t\bar{t}$ production threshold by the CMS and ATLAS collaborations suggests the existence of a color-singlet and $S$-wave quasi-bound state of top quark. Due to the non-relativistic nature of top and anti-top quarks in this threshold region, toponium production provides an ideal system to probe the anomalous dipole moments of the top quark. In this work, we investigate the impact of chromo-electric dipole moment (CEDM) in $t\bar{t}$-gluon vertex on toponium production at the LHC. We implement the enhanced near-threshold production of the spin-0 color-singlet toponium state $η_t$ via gluon fusion. The resonant toponium contribution is then combined with the continuum $t\bar{t}$ production amplitude, including the interference effects induced by the top CEDM. Furthermore, we construct a set of asymmetries based on the angular distributions of charged leptons in the leptonic decay channel of $t\bar{t}$. Finally, we derive the expected exclusion limit on the top quark CEDM parameter $d_t^g$ using these lepton angular asymmetries.

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Kai Ma, Tong Li. 2026-10-11. Probing the chromo-electric dipole moment of top quark near the toponium production threshold at LHC. https://arxiv.org/abs/2610.15493

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