München, Techn. University, Diss., 2003.

Bochum, University, Diss., 2002.

München, Techn. University, Diss., 2002.

München, Techn. University, Diss., 2002.

Karlsruhe, Univ., Diss., 2001.

This Thesis presents measurements of the decays \Bm\to\Xi_c^0\bar{\Lambda}_c^-, \Bzb\to\Xi_c^+\bar{\Lambda}_c^- , \Bm\to\Lambda_c^+\bar{\Lambda}_c^-\Km, and \Bzb\to\Lambda_c^+\bar{\Lambda}_c^-\Kzb based on 228 million \upsbb decays collected with the \babar\ detector at the SLAC \pep2\ asymmetric-energy \B factory. The branching fraction of \Bm\to\Lambda_c^+\bar{\Lambda}_c^-\Km is measured to be $(1.22\pm0.16\pm 0.14\pm0.63)\times 10^{-3}$, and the branching fraction of $\Bz\to\Lambda_c^+\bar{\Lambda_c^-\Kzb$ is $(0.40\pm 0.33\pm 0.05 \pm 0.21)\times 10^{-3}$. The product $\BR(\Bm\to\Xi_c^0\bar{Lambda}_c^-)\times \BR(\Xi_c^0\to\Xi^-\pi^+)$ is measured to be $(2.04\pm0.59\pm0.26\pm0.53)\times 10^{-5}$, and $\BR(\Bzb\to\Xi_c^+\bar{\Lambda}_c^-)\times\BR(\Xi_c^+\to\Xi^-\pi^+\pi^+)$ is $(1.50\pm 1.07\pm 0.19 \pm 0.39)\times 10^{-5}$, where the uncertainties are statistical, systematic, and the uncertainty from the branching fraction $\BR(\Lambda_c^+\to\proton K^-\pi^+)$, respectively.

Using data recorded by the CLEO II detector operating at the Upsilon(4S) resonance at the Cornell Electron Storage Ring, several properties of B mesons are measured using a partially reconstructed tag of the decay mode bar{B0} -> D*+ l- bar{nu}. Using 2.38 fb**{-1} of on-resonance data and the averaged B meson semileptonic branching fraction through inclusive lepton momentum spectrum obtained by previous CLEO analysis, we measure the B0 and B- semileptonic branching fraction to be (10.78 +/- 0.60 +/- 0.69)% and (10.25 +/- 0.57 +/- 0.65)% respectively, which yields the lifetime ratio tau_+/tau_0 = 0.950 +0.117-0.080 +0.091-0.068, assuming the equality of semileptonic partial branching width for bar{B0} and B-. With a larger dataset of 3.1 fb**{-1}, we measured the B0-bar{B0} mixing parameter chi_d to be 0.189 +/- 0.019 +/- 0.006. / Ph. D.

This thesis describes a search for the rare radiative decay of a B meson to two photons. where the charged congugate mode is implied throughout. These decays are highly suppressed in the Standard Model where the branching fraction is expected to be of order 10^-8. In some new physics scenarios this could be enhanced by up to an order of magnitude to 10^-7. Therefore an observation of a significant signal above the Standard Model prediction could be a sign of new physics. The search for this rare decay was performed using the data collected with the BaBar detector at the SLAC National Accelerator Laboratory PEP-II storage ring operating at the Upsilon(4S) resonance. The analysis uses a dataset with an integrated luminosity of 425.7 fb-1 corresponding to 467 million BB pairs. A signal yield of 21.3 +12.8 -11.8 events with a significance of 1.88 sigma was measured using an unbinned extended maximum likelihood fit. An upper limit on the branching fraction is set at the 90% confidence level of less than 3.2 times 10^-7. This is about two times more stringent than the best upper limit of less than 6.2 times 10^-7 published by the Belle collaboration. / text

Techn. Universiẗat, Diss., 1999--Dresden.

Techn. University, Diss., 2005--Dresden.