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

Sumitted to PubDB: 2023-06-14

Category: Master Thesis, Visibility: Public

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Authors	Thomas Kuhr, Thomas Lueck, Sofia Palacios Schweitzer
Date	Jan. 1, 2022
Belle II Number	BELLE2-MTHESIS-2023-032
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.
Conference	Munich