Session E8: B Factory Hadronic Decays and Vub

Measurement of BF($B^0\to\pi^-\ell^+\nu$) and BF($B^0\to\rho^-\ell^+\nu$) using neutrino reconstruction

We present an analysis of exclusively reconstructed charmless semileptonic $B$-meson decays based on 88 million $B \overline{B}$ pairs recorded with the BaBar detector at the PEP-II $e^+e^-$ storage rings. We study the four decay modes $B \rightarrow H_u \ell \nu$, where $H_u$ represents a $\pi^\pm, \pi^0, \rho^\pm$, or $\rho^0$, and $\ell$ is an electron or muon. The neutrino kinematics are inferred from the missing momentum and energy in the $B \overline{B}$ event. An extended maximum-likelihood fit is perfomed in bins of the three variables $\Delta E$, the reconstructed minus the expected $B$-meson energy; $m_{ES}$, the beam-energy substituted $B$~mass; and $q^2$, the squared four-momentum transfer, to determine the branching fractions $\mathcal{B} (B^0 \rightarrow \pi^- \ell^+ \nu)$ and $\mathcal{B} (B^0 \rightarrow \rho^- \ell^+ \nu)$ using isospin symmetry. The measured $q^2$ spectra are used to fit the $q^2$ dependence of the $B \rightarrow \pi (\rho) \ell \nu$ decay form factors and compare with theoretical predictions from light-cone sum rules, quark models and recent lattice QCD calculations. We extract the CKM matrix element $|V_{ub}|$ using the various theoretical calculations.   

Study of $B\to X_{u}\ell\nu$ Decays on the Recoil of Fully Reconstructed $B$ Mesons with the BaBar Experiment

We present a study of charmless semileptonic $B$ decays performed on the recoil of $B$ candidates fully reconstructed in hadronic decay modes. The semileptonic decays of the second $B$ meson are identified by the presence of an electron or a muon. The hadronic invariant mass, $m_{X}$, and the mass of the lepton pair, $q^2$ are used to discriminate charmless $B$ decays from charmed background. From this event sample the inclusive semileptonic branching fraction for charged and neutral $B$ mesons for $B\to X_{u}\ell\nu$ is measured and the CKM matrix element $|V_{ub}|$ is extracted. In addition, the unfolding of the hadronic mass spectrum and the measurement of several exclusive charmless semileptonic decays is discussed.   

Measurement of $\bar{B^0}\to\pi^+\ell^-\bar{\nu}$ on the recoil of partially reconstructed $B^0$ decays

We present a measurement of the branching fraction $\bar{B^0}\rightarrow \pi^+ \ell^- \bar{\nu_\ell}$ and of $|V_{ub}|$ from a sample of $\Upsilon(4S) \to B\bar{B}$ decays collected by the BaBar detector at the asymmetric $e^+e^-$ collider PEP-II. We search for events compatible with $\bar{B^0}\rightarrow \pi^+ \ell^- \bar{\nu_\ell}$ decay inside an enriched $\bar{B^0}B^0$ sample selected using partial reconstruction of the decay $B^0 \rightarrow D^{*-} \ell^+ \nu_\ell$. With this technique, we can perform softer cuts on pion and lepton momenta, as compared to untagged analyses, and therefore obtain a smaller systematic error due to the cut on the phase-space.   

Search for quark-annihilation type B-meson decays $B^- \to D_S^- \phi$ and B^- \to D_S^{*-} \phi$

We report on searches for $B^- \to D_S^- \phi$ and $B^- \to D_S^{*-} \phi$ based on 230 million $\Upsilon (4S) \rightarrow B\overline B$ decays collected with the BaBar detector at SLAC. The Standard Model branching fractions for these decays are expected to be highly suppressed since they proceed through annhilation of the $b$ and $\bar{u}$ quarks in the $B^-$ meson.   

Search for the decays $B^0 \rightarrow D_s^{(*)+} a^-_{0(2)}$

We report on a search for the decays $B0 \rightarrow D^{(*)+}_s a^-_{0(2)}$ using 210~$fb^{-1}$ of data collected at the $\Upsilon(4S)$ resonance by the $BaBar$ detector. This measurement will reduce theoretical uncertainties in the estimate of the $CP$ asymmetry in $B \rightarrow D^{(*)+} a^-_{0(2)}$ decays, and also will give an additional insight into the decay mechanisms of other two-body decay modes of $B$ mesons, containing an open charm and a light meson in the final state.   

Study of $B\to D^{(*)}(n\pi)$ Hadronic Decays

Based on the dataset of an integrated luminosity of $59.0 ~fb^{-1}$ taken with BaBar detector at $\Upsilon (4S)$ resonance, we study $B \to D^{(*)}\pi$, $B \to D^{(*)}\pi^{0}\pi$ and $B \to D^{(*)}\pi\pi\pi$ decays. These analyses are useful in $CP$ violation studies, test of the factorization hypothesis and Heavy Quark Effective Theory.   

A Search for $B^{0}_{d} \to D_{s}^{(*)-} D_{s}^{(*)+}$ Decays

We report on a search for the decays $B^{0}_{d} \to D_{s}^{(*)-} D_{s}^{(*)+}$ from a data sample of 232 million $\Upsilon(4S)$ decays into B meson pairs collected with the BaBar detector at the PEP-II asymmetric-energy $e^+ e^-$ collider.   

Search for exclusive two body decays $B \rightarrow {D_s}^{*} h$ at Belle

We report results of a search for $B^0 \rightarrow {D_s}^{*+} \pi^-$, $B^+ \rightarrow {D_s}^{*+} \pi^0$ and $\bar B^0 \rightarrow {D_s}^{*+} K^-$ in data collected at the $\Upsilon (4S)$ resonance by the Belle detector at the KEKB $e^+ e^-$ collider. $B^0 \rightarrow {D_s}^{*+} \pi^-$ and $B^+ \rightarrow {D_s}^{*+} \pi^0$ decays may be used to measure the magnitude of the CKM matrix element $V_{ub}$. The rate for the process $B^0 \rightarrow D_s^* \pi^+$ can be related to that for the process $B^0 \rightarrow D^{*+ }\pi^-$. The latter is needed to extract $\sin(2 \phi_1 + \phi_3)$ from a measurement of time-dependent CP asymmetries in $B \to D^* \pi$ decays. $\bar B^0 \rightarrow {D_s}^{*+} K^-$ decays may provide information on W-exchange diagrams and final state interactions. This search was performed using $2.75 \times 10^8$ $B \bar B$ pairs.   

Search for $B^+\to D^{(*)+}K_S^0$ decays

We report on the search for the decays $B^+ \rightarrow D^{(*)+} K^0_s$ using 205 $fb^{-1}$ of data collected at the $Y(4S)$ resonance by the $BABAR$ detector at the $Stanford$ $Linear$ $Accelerator$ $Center$. These decays are of interest since they are pure annihilation processes, a type of diagrams not yet measured in $B^+$ decays and so far not predicted by any theoretical model.