Measurement of the Branching Ratio $B \to D^{**} \ell \nu_{\ell}$ using the hadronic Full Event Interpretation with Belle II Data

Rauls, Noreen

doi:10.53846/goediss-10602

Measurement of the Branching Ratio $B \to D^{**} \ell \nu_{\ell}$ using the hadronic Full Event Interpretation with Belle II Data

Noreen Rauls
(
- Gottingen U.
)

Jul 17, 2024

167 pages

Supervisor:

Ariane Frey

Thesis: PhD

Gottingen U.

(2024)

Published: Jul 17, 2024

DOI:

10.53846/goediss-10602

URN/HDL:

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Abstract: (Gottingen U.)

The Belle II detector is situated at the asymmetric

e^{-}e^{+}

collider SuperKEKB at KEK in Tsukuba in Japan, which operates with an energy slightly above the mass of the Y(4S) resonance. As a result, pairs of B mesons are predominantly produced. Due to the clean experimental environment, various measurements to test the Standard Model and precisely determine its parameters can be performed. This is e.g. the element

V_{\mathrm{cb}}

of the CKM matrix among others, where one of the leading systematic uncertainties arises due to decays of the nature

B \to D^{**} \ell \nu_{\ell}

.This thesis presents the first measurement of the branching ratio

B \to D^{**} \ell \nu_{\ell}

using the data set collected with the Belle II detector between 2019 and 2022 and corresponds to about

364\;\mathrm{fb^{-1}}

of integrated luminosity at the Y(4S) resonance. To reconstruct the "other" B meson, a multivariate analysis tool called "Full Event Interpretation" is used, which reconstructs a variety of different hadronic decay modes. For the reconstruction of the signal side B meson, a light charged lepton is combined with a

D^{**}

meson that is reconstructed from various

D \pi

and

D^{*} \pi

combinations. In contrast to previously performed analyses, this analysis also takes the

\pi^0

into account in the reconstruction of the

D^{**}

meson.A selection of events is applied to obtain a sample enriched in

B \to D^{**} \ell \nu_{\ell}

decays and a binned maximum likelihood fit is performed to determine the branching ratio for the different

B \to D^{**} \ell \nu_{\ell}

decay channels. To account for effects in the simulation that are currently not well understood, the branching ratio is normalised to the branching ratio of the much more frequent decay

B \to D^{*} \ell \nu_{\ell}

.

530
Physik (PPN621336750)
Particle Physics
Belle II
Semileptonic B Decays

References(188)

Figures(0)

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