The CKM matrix element |Vus| can be extracted from the experimental measurement of semileptonic K → π decays and theoretical input for the corresponding vector form factor in QCD. The thesis performs a major improvement of the RBC/UKQCD programme to calculate Kl3 form factor in Nf = 2+1 Lattice QCD using domain wall fermions. We use data from several lattice spacings and dfferent quark masses with lightest pion mass of about 170MeV. Systematic error corresponding to interpolation in the momentum transfer is avoided using partially twisted boundary conditions. Using simulated quark masses near the physical point, reduce the systematic error due to the mass extrapolation. This work explores different kinematic arrangements of pion and Kaon momenta for twisted boundary conditions. This thesis proposes a new ansatz for mass extrapolation. Analysing three sets of simulation data allows for a detailed study of systematic effects leading to the prediction f+kπ (0) = 0:9671(17)(+18-46), where the first error is statistical and the second error systematic. The result allows us to extract the CKM matrix element |Vus| = 0:2237(+13-8) and confirm unitarity of the first row CKM matrix in the Standard Model. Also in this thesis, we discuss porting of Clover Lattice fermion action to Blue Gene-Q architecture. Clover action achieves maximum efficiency of 29.1% for single precision with good weak scaling. Strong scaling shows local volume dependency. In a study of different iterative solvers for Domain Wall Fermion action (DWF), we find that Modified Conjugate Residual(MCR) and Multishift MCR as the most efficient solver compared to CG and GCR. A new probing technique for estimating the diagonal of the inverse Dirac operator in Lattice QCD is introduced and this method is found to be closer to the exact solution than stochastic methods.

The branching fraction for B -> rho e nu decays and the CKM matrix element |Vub| is measured with semileptonic exclusive B-meson decays using approximately 55 million Upsilon(4S) -> BBbar decays collected during the years 2000 and 2001 with the BABAR detector. The result is Br(B0 -> rho- e+ nu) = (3.39 +- 0.44 +- 0.52 +- 0.60) x 10^-4, and |Vub| = (3.69 +- 0.23 +- 0.27 +0.40-0.59) x 10^-3. The quoted errors are statistical, systematic, and theoretical respectively. These are combined results obtained using five different form-factor models. Individual results are also quoted. / Das Verzweigungsverhältnis B -> rho e nu und das CKM Matrix Element |Vub| werden mittels semileptonischer exklusiver B Mesonen Zerfälle gemessen. Die Daten wurden in den Jahren 2000 und 2001 mit dem BABAR Dektektor aufgezeichnet und ensprechen ungefähr 55 Millionen Upsilon(4S) -> BBbar Zerfällen. Das Ergebnis ist Br(B0 -> rho- e+ nu) = (3.39 +- 0.44 +- 0.52 +- 0.60) x 10^-4 und |Vub| = (3.69 +- 0.23 +- 0.27 +0.40-0.59) x 10^-3. Die angegebenen Fehler sind statistisch, systematisch und theoretisch. Dieses Ergebnis ist eine Kombination von Ergebnissen fünf verschiedener Form-Faktor Modelle. Die Ergebnisse werden auch für jedes Modell einzeln angegeben.

An accurate determination of the angle γ of the Unitary Triangle is one of the most important goals of the LHCb experiment. The LHCb detector is a single-arm spectrometer at the LHC, optimised for beauty and charm flavour physics. As the angle γ is the least experimentally constrained parameter of the Unitary Triangle, its precise experimental determination can be used to test the validity of the Standard Model. The Unitary Triangle phase γ can be extracted in B → DK decays at tree-level, exploiting the interference between b → c(ūs) and b → u(c̄s) transitions. This interference is sensitive to γ and can give measurable charge asymmetries. In particular, γ ≠ 0 is required to produce direct CP violation in B decays and this is the only CP-violating mechanism for the decay of charged B^± mesons. In this thesis, an analysis of CP violation in B^± → DK^± and B^± → Dπ^± decays is presented, where the D meson is reconstructed in the two-body final states: K^±π^∓, K⁺K⁻, π⁺π⁻ and π^±K^∓. The analysis uses the full 2011 LHCb dataset of 1.0 fb^-1, collected from pp collisions at √s = 7 TeV. Several CP-related quantities, e.g the ratio of B → DK and B → Dπ branching fractions and their charge asymmetries, are measured via a simultaneous fit to the invariant mass distributions of the modes considered. The suppressed B^± → DK^± mode is observed for the first time with ≈ 10σ significance. Once all measurements are combined, direct CP violation is established in B^± decays with a total significance of 5.8σ.

Dresden, Techn. Univ., Diss., 2002.

No description available.

The flavor changing neutral current process b → dγ is a sensitive probe to the Standard Model of elementary particle physics. Using a sample of 386 × 10⁶ B meson pairs accumulated by the Belle detector at the KEKB e⁺e⁻ collider, we measure the branching fractions for the exclusive modes B⁻ → ρ⁻γ, B̅⁰ → ρ⁰γ and B̅⁰ → ωγ as follows: B(B⁻ → ρ⁻γ) = 0.55 _−0.36^+0.42_−0.08^+0.09 B(B̅⁰ → ρ⁰γ) = 1.25 _−0.33^+0.37_−0.06^+0.07 B(B̅⁰ → ωγ) = 0.56 _−0.27^+0.34_−0.10^+0.05 where the first error on each value is statistical and the second is systematic. Assuming that these three modes are related by isospin conservation rules, we find the combined branching fraction B(B̅ → (ρ,ω)γ) = 1.32 _−0.31^+0.34_−0.09^0.10. This result is used to determine the ratio of CKM matrix elements, |V_td/V_ts| = 0.199 _−0.025^+0.026_−0.015^0.018. / Ph. D.

The branching fraction for B -> rho e nu decays and the CKM matrix element |Vub| is measured with semileptonic exclusive B-meson decays using approximately 55 million Upsilon(4S) -> BBbar decays collected during the years 2000 and 2001 with the BABAR detector. The result is Br(B0 -> rho- e+ nu) = (3.39 +- 0.44 +- 0.52 +- 0.60) x 10^-4, and |Vub| = (3.69 +- 0.23 +- 0.27 +0.40-0.59) x 10^-3. The quoted errors are statistical, systematic, and theoretical respectively. These are combined results obtained using five different form-factor models. Individual results are also quoted. / Das Verzweigungsverhältnis B -> rho e nu und das CKM Matrix Element |Vub| werden mittels semileptonischer exklusiver B Mesonen Zerfälle gemessen. Die Daten wurden in den Jahren 2000 und 2001 mit dem BABAR Dektektor aufgezeichnet und ensprechen ungefähr 55 Millionen Upsilon(4S) -> BBbar Zerfällen. Das Ergebnis ist Br(B0 -> rho- e+ nu) = (3.39 +- 0.44 +- 0.52 +- 0.60) x 10^-4 und |Vub| = (3.69 +- 0.23 +- 0.27 +0.40-0.59) x 10^-3. Die angegebenen Fehler sind statistisch, systematisch und theoretisch. Dieses Ergebnis ist eine Kombination von Ergebnissen fünf verschiedener Form-Faktor Modelle. Die Ergebnisse werden auch für jedes Modell einzeln angegeben.

This thesis presents first measurements of moments of the hadronic n_X^2 distribution measured in inclusive semileptonic decays of B mesons to final states containing a charm quark, B->Xc l nu. The variable n_X^2 is a combination of the invariant mass of the charmed meson m_X, its energy in the B-meson rest-frame E_X, and a constant \tilde{\Lambda} = 0.65 GeV, n_X^2 = m_X^2 c^4 - 2 \tilde{\Lambda} E_X + \tilde{\Lambda}^2. The moments <n_X^k> with k=2,4,6 are measured as proposed by theory to constrain assumptions made in the theoretical description of inclusive observables in semileptonic B-meson decays. This description uses Heavy Quark Expansion (HQE), an effective QCD combined with an Operator Product Expansion. The measurement is based on a sample of 231.6 million e+e- -> Y(4S) -> B\bar{B} events recorded with the BABAR experiment at the PEP-II e+e--storage rings at SLAC. We reconstruct the semileptonic decay by identifying a charged lepton in events tagged by a fully reconstructed hadronic decay of the second B meson. Correction procedures are derived from Monte Carlo simulations to ensure an unbiased measurement of the moments of the n_X^2 distribution. All moments are measured requiring minimum lepton momenta between 0.8 GeV/c and 1.9 GeV/c in the rest frame of the B meson. Performing a simultaneous fit to the measured moments <n_X^k> up to order k=6 combined with other measurements of moments of the lepton-energy spectrum in decays B->Xc l nu and moments of the photon-energy spectrum in decays B->Xs gamma, we determine the quark-mixing parameter |V_{cb}|, the bottom and charm quark masses, the semileptonic branching fraction BR(B->X l nu), and four non-perturbative heavy quark parameters. Using HQE calculations in the kinetic scheme up to order 1/m_b^3 we find |V_{cb}| = (41.65 +- 0.43 +- 0.40 +- 0.58) x 10^{-3} and m_b = (4.570 \pm 0.033 \pm 0.043)GeV/c^2, where the first uncertainty refers to experimental contributions, the second to uncertainties in the HQE, and the third to theoretical uncertainties in the calculations of the semileptonic decay rate. All obtained results are consistent with previous determinations. The inclusion of the moments <n_X^6> decreases the uncertainty on the HQE parameters mu_{pi} and rho_{D}. Furthermore, the theoretical treatment of higher order corrections in the HQE used for the moments <m_X^k> has been verified with these new measurements.

This thesis presents first measurements of moments of the hadronic n_X^2 distribution measured in inclusive semileptonic decays of B mesons to final states containing a charm quark, B->Xc l nu. The variable n_X^2 is a combination of the invariant mass of the charmed meson m_X, its energy in the B-meson rest-frame E_X, and a constant \tilde{\Lambda} = 0.65 GeV, n_X^2 = m_X^2 c^4 - 2 \tilde{\Lambda} E_X + \tilde{\Lambda}^2. The moments <n_X^k> with k=2,4,6 are measured as proposed by theory to constrain assumptions made in the theoretical description of inclusive observables in semileptonic B-meson decays. This description uses Heavy Quark Expansion (HQE), an effective QCD combined with an Operator Product Expansion. The measurement is based on a sample of 231.6 million e+e- -> Y(4S) -> B\bar{B} events recorded with the BABAR experiment at the PEP-II e+e--storage rings at SLAC. We reconstruct the semileptonic decay by identifying a charged lepton in events tagged by a fully reconstructed hadronic decay of the second B meson. Correction procedures are derived from Monte Carlo simulations to ensure an unbiased measurement of the moments of the n_X^2 distribution. All moments are measured requiring minimum lepton momenta between 0.8 GeV/c and 1.9 GeV/c in the rest frame of the B meson. Performing a simultaneous fit to the measured moments <n_X^k> up to order k=6 combined with other measurements of moments of the lepton-energy spectrum in decays B->Xc l nu and moments of the photon-energy spectrum in decays B->Xs gamma, we determine the quark-mixing parameter |V_{cb}|, the bottom and charm quark masses, the semileptonic branching fraction BR(B->X l nu), and four non-perturbative heavy quark parameters. Using HQE calculations in the kinetic scheme up to order 1/m_b^3 we find |V_{cb}| = (41.65 +- 0.43 +- 0.40 +- 0.58) x 10^{-3} and m_b = (4.570 \pm 0.033 \pm 0.043)GeV/c^2, where the first uncertainty refers to experimental contributions, the second to uncertainties in the HQE, and the third to theoretical uncertainties in the calculations of the semileptonic decay rate. All obtained results are consistent with previous determinations. The inclusion of the moments <n_X^6> decreases the uncertainty on the HQE parameters mu_{pi} and rho_{D}. Furthermore, the theoretical treatment of higher order corrections in the HQE used for the moments <m_X^k> has been verified with these new measurements.

Two measurements of the Cabibbo-Kobayashi-Maskawa angle &gamma; using B &rarr; DK and B⁰ &rarr; DK^&ast;0 decays are presented in this thesis. The subsequent D meson decays to the K_S⁰&pi;⁺&pi;^− and K_S⁰K⁺K^− final states are studied using a binned Dalitz plot analysis. The D strong-phase variation over the Dalitz plot is taken from measurements performed at the CLEO-c experiment, making the analysis independent of a model to describe the D decay amplitude. Both measurements are performed using proton-proton collision data collected by the Large Hadron Collider beauty (LHCb) experiment in 2011 and 2012, corresponding to an integrated luminosity of 3 fb^−1 at centre-of-mass energies &radic;s = 7 TeV and 8 TeV. The value &gamma;= (62 ⁺¹⁵<sub style='position: relative; left: -1.7em;'>−14</sub>)° is measured using B⁰ &rarr; DK^&ast;0 decays and &gamma; = (71 ± 20)° is measured using B⁰ &rarr; DK^&ast;0 decays, with a second solution for each value corresponding to &gamma; + 180°. The measurements are consistent with the world average value of &gamma;.