Search for scalar and vector leptoquarks decaying into quarks and leptons of different generations

A search for pairs of leptoquarks produced in proton-proton collisions at a centre-of-mass energy of 13 TeV is presented. The data set, recorded with the ATLAS detector at the Large Hadron Collider, corresponds to an integrated luminosity of 139 fb$^{-1}$. The leptoquarks are assumed to decay only into quarks of the third generation and leptons of the first or the second generation. In particular, final states containing exactly one highly-energetic electron or muon are targeted. Additionally, events of interest contain large amounts of missing transverse momentum. These characteristics allow for an efficient discrimination against background events. Contributions from background processes are further suppressed through the application of neural networks, trained separately for various signal hypotheses. In total, eight different signal models are considered. In the absence of significant deviations between observed data and predictions based on the Standard Model of Particle Physics, exclusion limits on the signal models are derived. Finally, results from a statistical combination with other searches for leptoquarks are presented.