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T: Fachverband Teilchenphysik
T 60: Top Quarks: Decay and CP Violation and Mixing Angles
T 60.5: Talk
Wednesday, March 23, 2022, 17:15–17:30, T-H19
Search for charged lepton flavour violation in top-quark production and decay with the ATLAS experiment at 13 TeV — Markus Cristinziani1, William George2, •Gabriel Gomes1, Carlo Gottardo3, Chris Hawkes2, Jacob Kempster2, Alexios Stampekis2, and Miriam Watson2 — 1Center for Particle Physics Siegen, Experimentelle Teilchenphysik, Universität Siegen — 2University of Birmingham — 3NIKHEF
In the Standard Model (SM) with massless neutrinos, the flavour of charged leptons cannot be altered in weak interactions. However, the observed neutrino oscillations allow for charged lepton flavour violating (cLFV) processes, even though highly suppressed. Hence, experimental evidence of such rare processes would provide signs of new physics beyond the SM.
Investigations targeting a direct search for cLFV will be presented using proton–proton collision data collected by the ATLAS detector between 2015 and 2018 at √s = 13 TeV. Decays of a top quark into a pair of opposite-sign different-flavour (OSDF) leptons and an up-type quark, as well as single top-quark production in association with an OSDF dilepton pair, are examined. Thus, besides the top-quark decay channel, the single top-quark production channel is included, providing additional sensitivity. For signal-discrimination purposes, a multivariate discriminant, namely a boosted decision tree, is implemented and optimised.