UC Santa Cruz

A search for the production of top-quark pairs with the same electric charge (tt or tt¯$$ \overline{tt} $$) is presented. The analysis uses proton-proton collision data at s$$ \sqrt{s} $$ = 13 TeV, recorded by the ATLAS detector at the Large Hadron Collider, corresponding to an integrated luminosity of 140 fb−1. Events with two same-charge leptons and at least two b-tagged jets are selected. Neural networks are employed to define two selections sensitive to additional couplings beyond the Standard Model that would enhance the production rate of same-sign top-quark pairs. No significant signal is observed, leading to an upper limit on the total production cross-section of same-sign top-quark pairs of 1.6 fb at 95% confidence level. Corresponding limits on the three Wilson coefficients associated with the Otu1$$ {\mathcal{O}}_{tu}^{(1)} $$, OQu1$$ {\mathcal{O}}_{Qu}^{(1)} $$, and OQu8$$ {\mathcal{O}}_{Qu}^{(8)} $$ operators in the Standard Model Effective Field Theory framework are derived.