Search for leptoquarks through tτtτ final state with the ATLAS detector

by Stergios Kazakos (IFAE)

Wednesday Jan 27, 2021, 1:00 PM → 2:00 PM Europe/Madrid

IFAE Virtual Seminar Room (IFAE)

Leptoquarks are the most favored BSM scenario supported by many theorists as the best possible interpretation to describe B-physics anomalies. This analysis is targeting at scalar leptoquark pair production with a mass in the TeV scale coupling to top quarks and τ-leptons. Since the final state is characterised by the presence of multiple leptons and b-jets, a significant effort is required to control the different types of background consisted mainly of tt events with non-prompt leptons from photon conversions or semileptonic b-quark decays. In addition, this particular analysis utilises the inclusion of τ-leptons, which were often overlooked in similar analyses in the past.Due to the increased complexity of these experimental signatures a sophisticated event categorisation is performed by introducing signal and control regions considering combinations of different lepton multiplicities and hadronically decaying τ-leptons. This type of categorization is effectively probing the targeted signal signature, while helping isolate low-background regions in which any significant excess would constitute a solid probe for new physics. Unfortunately due to no such excess after unblinding, upper limits were set to the signal cross-section (σ_{LQLQ}xBR^{2}) and the branching ratio as a function of the leptoquark mass.