Aachen 2019 – wissenschaftliches Programm
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T: Fachverband Teilchenphysik
T 14: Elektroschwache Wechselwirkung
T 14.2: Vortrag
Montag, 25. März 2019, 16:20–16:35, S14
Testing the lepton universality in the W-boson decay with the ATLAS detector — Philip Bechtle1, Klaus Desch1, Andreas Düdder2, •Philipp König1, and Matthias Schott2 — 1Rheinische Friedrich-Wilhelms-Universität Bonn — 2Johannes Gutenberg Universität Mainz
Lepton universality is preserved by the electroweak interaction in the Standard Model (SM). The Higgs mechanism breaks this universality, and thus many new physics models yield small deviations in the predictions for precision tests on lepton universality. A measured deviation of the branching fraction BR(W→τν) from the SM prediction would therefore be an indicator for new physics which is expected to couple predominantly to heavier particles. Experimentally, it is preferable to measure the ratio of the branching fractions of the tau lepton decay compared to the decay to the lighter leptons. The analysis presented here goes one step further and measures BR(W→τντ→µνµντντ)/BR(W→µνµ). This allows to cancel many systematic uncertainties by using the same final state. However, it implies that enumerator and denominator only differ in kinematic distributions from which the result is extracted in a fit. Characteristic observables being important for the fitting procedure will be introduced as well as possibilities to further increase the sensitivity of the measurement. Finally, it is investigated how competitive the obtained sensitivity is compared to previous measurements by other experiments.