Search for charged-lepton-flavor violating μτqt interactions in top-quark production and decay in pp collisions at sqrt(s) = 13 TeV with the ATLAS detector at the LHC

A search for charged-lepton-flavor violating mutauqt (q=u,c) interactions is presented, considering both top-quark production and decay. The data analyzed correspond to 140  fb-1 of proton-proton collisions at a center-of-mass energy of sqrt(s)=13  TeV recorded with the ATLAS detector at the Large Hadron Collider. The analysis targets events containing two muons with the same electric charge, a hadronically decaying tau-lepton and at least one jet, with exactly one b-tagged jet, produced by a ⁢mutauqt interaction. Agreement with the Standard Model expectation within 1.6 standard deviations is observed, and limits are set at the 95% confidence level (CL) on the charged-lepton-flavor violation branching ratio of B(t->mutauq) <8.7 ×10−7. An effective field theory interpretation is performed yielding 95% CL limits on Wilson coefficients, dependent on the flavor of the associated light quark and the Lorentz structure of the coupling. These range from |c3⁢(2313)|/Λ2 <0.10  TeV−2 for mutauut to |c1⁢(2323)0|/Λ2 <1.8  TeV−2 for mutauct. An additional interpretation is performed for scalar leptoquark production inducing charged-lepton-flavor violation, with fixed intergenerational couplings. Upper limits on leptoquark coupling strengths are set at the 95% CL, ranging from lambdaLQ =1.3 to lambdaLQ =3.7 for leptoquark masses between 0.5 and 2.0 TeV.