Thesis BELLE2-MTHESIS-2019-004

Exclusive untagged analysis of the semi-leptonic decay B→ρlν in preparation for extracting |V_ub| using early Belle II data

Lex Greeven ; Prof. Dr. Jochen Dingfelder ; Dr. Peter Lewis

Physikalisches Institut Bonn

Abstract: In this thesis, the decay B → ρlν was studied using Belle II Monte Carlo simulation corresponding to the early Belle II data size of 6.5 fb−1. Selections were performed to reduce background events, and BDTs were trained to further reject continuum and BB background events. It was found that performing a FOM selection on the BDT output classifiers lead to highly correlated signal and background shapes in ∆E and M_bc, so instead the BDT output classifiers were fitted. It was found that a significant branching fraction measurement was not possible with the current data set, and at least 16 fb−1 is required for the ‘evidence’ of B → ρlν at Belle II. Due to time limitations, further study on the systematic uncertainties of this analysis could not be performed, but the major sources are expected to be the MC modeling of the detector response,the MC modeling of continuum, and the modeling of inclusive Xu background. Early Belle II data showed disagreements compared to the MC that was used, indicating that further studies by the Belle II detector groups are required to fully understand the data before a meaningful signal extraction on data is possible performed.

Note: Presented on 01 08 2019
Note: MSc

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 Record created 2019-08-01, last modified 2019-08-01

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