Aachen 2019 – scientific programme
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T: Fachverband Teilchenphysik
T 35: Top-Physik I
T 35.7: Talk
Tuesday, March 26, 2019, 17:30–17:45, S10
Search for charged lepton-flavour violation in top-quark decays at the LHC with the ATLAS detector — Carlo A. Gottardo, Sebastian Heer, Vadim Kostyukhin, Ö. Oğul Öncel, Keshava Prasad, Andrea Sciandra, and •Markus Cristinziani — Physikalisches Institut, Universität Bonn
A direct search for charged lepton-flavour violation in top-quark decays is presented. The data analysed correspond to 79.8 fb−1 of proton–proton collisions at a centre-of-mass energy of √s=13 TeV delivered by the LHC. The process studied is the production of top-quark pairs, where one top quark decays into a pair of opposite-sign different-flavour charged leptons and an up-type quark, while the other decays semileptonically according to the Standard Model. The signature of the signal is thus characterised by the presence of three charged leptons, a light jet and a b-jet. A multivariate discriminant is deployed and its distribution used as input to extract the signal strength. In the absence of a signal, an upper limit on the branching ratio of BF( t → ℓ ℓ′ q) < 1.86 · 10−5 is set at 95% confidence level.