Measuring the Weinberg Angle at the Belle II Experiment

Sumitted to PubDB: 2024-04-15

Category: Master Thesis, Visibility: Public

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Authors	Daniel Greenwald, Lukas Grussbach, Stephan Paul
Date	Jan. 1, 2022
Belle II Number	BELLE2-MTHESIS-2024-010
Abstract	The Weinberg angle is known precisely only at high energies around the Z0 mass. At Belle II, we have the opportunity to measure it at much lower energies via e+e− → μ+μ− as a process. A measurement could solve the issue of the deviation observed by the NuTeV experiment. I calculate the differential cross section for this process at tree-level to relate the Weinberg angle to the polar angle distribution of the muons. This calculation is used in a dedicated software that I developed to fit the differential cross section to the polar angle distribution and extract the Weinberg angle. I study different background sources and criteria to select signal events and reject background events. By calculating muon detection efficiencies, I study the muon identification performance of Belle II in the process e+e− → μ+μ−γ both in recorded data and using simulation. The ratio of the efficiencies in recorded data and simulation allows us to correct differences between recorded and simulated data and provides systematic uncertainties related to these corrections.
Conference	Munich