Measurement of the Partial Branching Fraction for Inclusive Semileptonic B Meson Decays to Light Hadrons B->Xu l nu and an Improved Determination of the Quark-Mixing Matrix Element |V_ub|

This thesis presents an analysis of inclusive semileptonic B \to X_u e \nu decays using approximately 454 million $\Upsilon(4S) \to B \bar{B}$ decays collected during the years 1999 to 2008 with the BABAR detector. The electron energy, E_e, and the invariant mass squared of the electron-neutrino pair, q², are reconstructed, where the neutrino kinematics is deduced from the decay products of both B mesons. The final hadronic state, X_u, consists of a sum of many hadronic channels, each of which contains at least one $u$ quark. The variables q² and E_e are then combined to compute the maximum kinematically allowed invariant mass squared of the hadronic system, s_h^max. Using these kinematic quantities, the partial branching fraction, \Delta BR(B \to X_u e \nu), unfolded for detector effects, is measured to be \Delta BR(E_e>2.0 GeV, s_h^max<3.52 GeV²) = (3.33 \pm 0.18 \pm 0.21) \times 10^-4 in the \Upsilon(4S) and \Delta \tilde{\BR}(\tilde E_e>1.9 GeV, \tilde {s}^max_h < 3.5 GeV²) = (4.57 \pm 0.24 \pm 0.32) \times 10^-4 in the B$ meson rest frames. The quoted errors are statistical and systematic, respectively. The CKM matrix element $|V_{ub}|$ is determined from the measured $\Delta \tilde{\BR}$ using theoretical calculation based on Heavy Quark Expansion. The result is $|V_{ub}| = (4.19 \pm 0.18{}^{+0.26}_{-0.20} {}^{+0.26}_{-0.25}) \times 10^{-3}, where the errors represent experimental uncertainties, uncertainties from HQE parameters and theoretical uncertainties, respectively.

Level thesis:degree_level

thesis.doctoral

Grantor dc:publisher

Technische Universität Dresden

Year

2009

Author dc:creator

• Volk, Alexei

Contributors dc:contributor

• Kobel, Michael
• Lacker, Heiko

• CKM matrix element
• semileptonic B decays
• semileptonische B-Meson Zerfälle
• CKM-Matrixelement