Measurements of q2 moments of inclusive B → Xcℓν decays toward an alternative determination of |Vcb|
Measurements of q2 moments of inclusive B → Xcℓν decays toward an alternative determination of |Vcb|
Dokument öffnen (9.6MB)Art der Hochschulschrift
DissertationPrüfungsdatum
22.11.2021Datum der Veröffentlichung
06.12.2021Erstgutachter
Bernlochner, FlorianZweitgutachter
Dingfelder, JochenMetadaten
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Inhalt
This thesis presents the first measurement of the first to the fourth moments of the four-momentum transfer squared q2 spectrum for inclusive B → Xcℓν decays, where ℓ = e, μ. The determination of these moments and their systematic uncertainties are crucial experimental inputs for a novel, alternative method to determine the magnitude of the CKM matrix element Vcb using a reduced set of hadronic matrix elements in the heavy quark expansion. The analysis investigates the complete ϒ(4S) data set collected by the Belle detector, corresponding to 711 fb-1 of integrated luminosity and a total of (772 ± 10) × 106 B meson pairs. To identify and reconstruct the kinematic variables of inclusive semileptonic B meson decays, machine learning techniques are employed to fully reconstruct one of the B mesons in purely hadronic decay modes. Consequently, this approach allows for the kinematics of the remaining B meson to be inferred using conservation laws leading to the explicit reconstruction of the hadronic Xc system and, in turn, the q2 spectrum. The moments are measured with progressively increasing threshold selections on q2: from q2 > 3.0 GeV2 to q2 > 10.0 GeV2 while incrementing the threshold in 0.5 GeV2 steps. To ensure an unbiased result, the measured moments are unfolded and corrected for reconstruction and selection effects. The measured moments are reported separately for electron and muon final states, allowing for a test of lepton flavour universality. No deviation from the expectation of unity is observed. In addition, the presented measurement is combined with theoretical predictions of the ⟨qn⟩ moments and the semileptonic decay rate up to order 1/mb4 to perform a simultaneous fit and extract |Vcb| in a data-driven manner. A value of |Vcb| × 103 = 41.7 ± 1.2 is obtained, which is consistent with previous determinations within experimental uncertainty.
Schlagwörter
Hochenergiephysik, B-Physik, Elementarteilchenphysik, Belle-Experiment, Semileptonische Zerfälle
Klassifikation (DDC)
530 Physikvan Tonder, Raynette: Measurements of q2 moments of inclusive B → Xcℓν decays toward an alternative determination of |Vcb|. - Bonn, 2021. - Dissertation, Rheinische Friedrich-Wilhelms-Universität Bonn.
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-64713
Online-Ausgabe in bonndoc: https://nbn-resolving.org/urn:nbn:de:hbz:5-64713
@phdthesis{handle:20.500.11811/9447,
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-64713,
author = {{Raynette van Tonder}},
title = {Measurements of q2 moments of inclusive B → Xcℓν decays toward an alternative determination of |Vcb|},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2021,
month = dec,
note = {This thesis presents the first measurement of the first to the fourth moments of the four-momentum transfer squared q2 spectrum for inclusive B → Xcℓν decays, where ℓ = e, μ. The determination of these moments and their systematic uncertainties are crucial experimental inputs for a novel, alternative method to determine the magnitude of the CKM matrix element Vcb using a reduced set of hadronic matrix elements in the heavy quark expansion. The analysis investigates the complete ϒ(4S) data set collected by the Belle detector, corresponding to 711 fb-1 of integrated luminosity and a total of (772 ± 10) × 106 B meson pairs. To identify and reconstruct the kinematic variables of inclusive semileptonic B meson decays, machine learning techniques are employed to fully reconstruct one of the B mesons in purely hadronic decay modes. Consequently, this approach allows for the kinematics of the remaining B meson to be inferred using conservation laws leading to the explicit reconstruction of the hadronic Xc system and, in turn, the q2 spectrum. The moments are measured with progressively increasing threshold selections on q2: from q2 > 3.0 GeV2 to q2 > 10.0 GeV2 while incrementing the threshold in 0.5 GeV2 steps. To ensure an unbiased result, the measured moments are unfolded and corrected for reconstruction and selection effects. The measured moments are reported separately for electron and muon final states, allowing for a test of lepton flavour universality. No deviation from the expectation of unity is observed. In addition, the presented measurement is combined with theoretical predictions of the ⟨qn⟩ moments and the semileptonic decay rate up to order 1/mb4 to perform a simultaneous fit and extract |Vcb| in a data-driven manner. A value of |Vcb| × 103 = 41.7 ± 1.2 is obtained, which is consistent with previous determinations within experimental uncertainty.},
url = {https://hdl.handle.net/20.500.11811/9447}
}
urn: https://nbn-resolving.org/urn:nbn:de:hbz:5-64713,
author = {{Raynette van Tonder}},
title = {Measurements of q2 moments of inclusive B → Xcℓν decays toward an alternative determination of |Vcb|},
school = {Rheinische Friedrich-Wilhelms-Universität Bonn},
year = 2021,
month = dec,
note = {This thesis presents the first measurement of the first to the fourth moments of the four-momentum transfer squared q2 spectrum for inclusive B → Xcℓν decays, where ℓ = e, μ. The determination of these moments and their systematic uncertainties are crucial experimental inputs for a novel, alternative method to determine the magnitude of the CKM matrix element Vcb using a reduced set of hadronic matrix elements in the heavy quark expansion. The analysis investigates the complete ϒ(4S) data set collected by the Belle detector, corresponding to 711 fb-1 of integrated luminosity and a total of (772 ± 10) × 106 B meson pairs. To identify and reconstruct the kinematic variables of inclusive semileptonic B meson decays, machine learning techniques are employed to fully reconstruct one of the B mesons in purely hadronic decay modes. Consequently, this approach allows for the kinematics of the remaining B meson to be inferred using conservation laws leading to the explicit reconstruction of the hadronic Xc system and, in turn, the q2 spectrum. The moments are measured with progressively increasing threshold selections on q2: from q2 > 3.0 GeV2 to q2 > 10.0 GeV2 while incrementing the threshold in 0.5 GeV2 steps. To ensure an unbiased result, the measured moments are unfolded and corrected for reconstruction and selection effects. The measured moments are reported separately for electron and muon final states, allowing for a test of lepton flavour universality. No deviation from the expectation of unity is observed. In addition, the presented measurement is combined with theoretical predictions of the ⟨qn⟩ moments and the semileptonic decay rate up to order 1/mb4 to perform a simultaneous fit and extract |Vcb| in a data-driven manner. A value of |Vcb| × 103 = 41.7 ± 1.2 is obtained, which is consistent with previous determinations within experimental uncertainty.},
url = {https://hdl.handle.net/20.500.11811/9447}
}
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