Estimation of backgrounds from jets misidentified as $\tau$-leptons using the Universal Fake Factor method with the ATLAS detector($^\ast$)

Physical processes with $\tau$-leptons are increasingly relevant for the physics program of the ATLAS experiment at the Large Hadron Collider. The usage of hadronic channels, in which $\tau$-leptons decay into one or more hadrons, enables to exploit the large statistics associated with hadronic $\tau$-lepton decays, but requires a precise estimate of a sizeable background of hadronic jets misreconstructed as fake $\tau$-leptons. The Universal Fake Factor method is the technique recently developed in the ATLAS Collaboration to estimate the fake $\tau$-lepton background from data. Details on its implementation are presented as well as on its validation with final states containing one or two hadronically decaying $\tau$-leptons.