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T: Fachverband Teilchenphysik
T 21: Electroweak physics I
T 21.4: Vortrag
Montag, 30. März 2020, 17:15–17:30, L-3.016
Measuring the lepton universality, the mass and the width in the W-boson decay with the ATLAS detector — Lennart Adam2, Nassim Ainouz1, Philip Bechtle1, Klaus Desch1, Jakub Kremer2, •Philipp König1, and Matthias Schott2 — 1Rheinische Friedrich-Wilhelms-Universität Bonn — 2Johannes Gutenberg-Universität Mainz
The ATLAS collaboration measured the W-boson mass based on data taken with 7 TeV in 2017 in the most precise single measurement with a precision of 19 MeV. The analysis presented goes one step further and tries to improving the fitting methods and by measuring also the width of the W-boson. These quantities and the test of the lepton universality in the decay of the W-boson are an excellent precision test of the Standard Model (SM).
A measured deviation of the branching fraction BR(W→τν) from the SM prediction would 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 ratios of the tau lepton decay into light leptons compared to the direct W decay into light leptons. 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.