Heidelberg 2022 – wissenschaftliches Programm

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T: Fachverband Teilchenphysik

T 8: Higgs Boson: Decay in Fermions 1

T 8.8: Vortrag

Montag, 21. März 2022, 18:00–18:15, T-H21

Search for lepton-flavour violating decays of the Higgs boson using the symmetry method for background estimation with the ATLAS experiment at √s=13 TeV — •Katharina Schleicher, Valerie Lang, and Markus Schumacher — Albert-Ludwigs-Universität Freiburg

The discovery of the Higgs boson opened the window to a variety of interesting probes to physics beyond the standard model (SM), including searches for lepton-flavour violating (LFV) Higgs-boson decays. Such decays are predicted in several extension of the SM e.g. in models with two Higgs doublets. In nature, LFV was already observed in form of neutrino oscillations. In this analysis the decays of H→ eτ and H→µτ with leptonic τ-decays leading to eµ+2ν final states are considered. A central part of the analysis is the precise estimation of the SM backgrounds. Therefore, a data-driven method is used - the so-called symmetry method. It exploits two principles: First, SM backgrounds with prompt leptons are symmetric w.r.t. the interchange of electrons and muons. And second, this symmetry is broken if the branching ratios of the two LFV decays are of different magnitude. The first principle implicates the challenge of restoring this symmetry since electrons and muons are experimentally different. The second principle is motivated by the upper limit on the BR(µ → eγ). To obtain the best possible sensitivity, a dedicated statistical model was developed and neural networks for classification are deployed. In this talk, an overview of the analysis using the LHC Run-2 dataset recorded with the ATLAS detector in pp collisions at √s=13 TeV is given.