Search for same-charge top-quark pair production in pp collisions at $$ \sqrt{\textrm{s}} $$ = 13 TeV with the ATLAS detector

A search for the production of top-quark pairs with the same electric charge (tt or t¯t¯) is presented. The analysis uses proton-proton collision data at root 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 defne 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% confdence level. Corresponding limits on the three Wilson coefficients associated with the O^(1)_tu , O^(1)_Qu, and O^(8)_Qu operators in the Standard Model Effective Field Theory framework are derived.