engKoch, Simon FlorianMeasurement of the high-mass tau-tau production cross-section and constraints on Leptoquarks, Z' bosons, and effective couplingsParticle Physics - ExperimentATL-PHYS-SLIDE-2025-404The production of high-mass 𝜏-lepton pairs constitutes a very effective process to probe the Standard Model flavour sector and to search for new physics. The first measurement of the high-mass $\tau \bar{\tau}$ production cross section is presented, performed by the ATLAS Collaboration with the dataset of 140 fb-1 of pp collisions at $\sqrt{s} = 13$~TeV. New physics models are constrained through a fit to the di-tau invariant mass distribution as a function of b-jet multiplicity. Exclusion contours are presented, constraining the leptoquark models proposed to interpret the flavour anomalies in B hadron decays, as well as the production of Z’ bosons that couple preferentially to third-generation fermions. Additionally, constraints on effective field theory operators describing new particles are presented, including those affecting g-2 of the 𝜏 lepton.2025-08-28http://cds.cern.ch/record/2941224Physicshttp://cds.cern.ch/record/2941224oai:cds.cern.ch:2941224