Thesis BELLE2-MTHESIS-2023-032

Inclusive B-Meson Tagging for an R(D*) Measurement at Belle II

Sofia Palacios Schweitzer ; Thomas Kuhr ; Thomas Lueck

LMU Munich

Abstract: The world average of previous R(D(*)) measurements, defined as R(D(*)) = BR(B -> D(*) tau nu) / BR(B -> D(*) l nu) with l = e, mu, shows a 3.3 sigma deviation from Standard Model predictions, which could indicate some New Physics phenomenon, such as the existence of Leptoquarks. This analysis uses simulations from the Belle II experiment at the SuperKEKB electron-positron collider to measure R(D*). To account for the challenge of multiple neutrinos as final state particles, an approach is considered, where besides the signal B-meson decay kinematical and topological properties of the other B-meson are reconstructed fully inclusively. In contrast to an exclusive reconstruction of the second B-meson used for previous R(D*) measurements by the B-factories, this inclusive approach suffers from a larger background, but also offers a higher reconstruction efficiency. As part of the analysis machine learning methods are studied to suppress different background sources. R(D*) is extracted from a two-dimensional extended maximum likelihood fit.

Note: Presented on 13 09 2022
Note: MSc

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 Record created 2023-06-14, last modified 2023-06-14

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