Session E12: B Physics II

Search for the Radiative Decays $B\to \Lambda \bar{p} \gamma$ and $B\to \Sigma^0 \bar{p} \gamma$

We report the results of a search for the radiative baryonic decays $B\to \Lambda \bar{p} \gamma$ and $B\to \Sigma^0 \bar{p} \gamma$ in a sample of 380 million $B$ decays recorded at the $\Upsilon(4S)$ resonance of the PEP-II facility with the BaBar detector. We present branching fractions for these channels and investigate mass and angular distributions of the di-baryon system, which provide insight into the decay mechanism.   

Technique for an improved measurement of the $\Upsilon(4S) \to B^0 \bar{B}^0$ branching fraction

We present a technique for improving the determination of the $\Upsilon(4S) \to B^0 \bar{B}^0$ branching fraction using data collected by the BaBar detector at the PEP-II asymmetric-energy $e^+ e^-$ collider at SLAC. We present the projected precision of the improved measurement and what can be learned from such a measurement.   

Measurement of the Branching Fraction of $\bar{B}^0 \to D^{*+}\ell^- \bar \nu$ by Partial Reconstruction

We present the branching fraction measurement of $\bar{B}^0 \to D^{*+}\ell^- \bar \nu$ using data collected with the BaBar detector at the PEP-II $e^+e^-$ storage rings at the Stanford Linear Accelerator. We conduct the measurement by partially reconstructing the $D^{*+}$ mesons from $\bar{B}^0 \to D^{*+}\ell^- \bar \nu$ decays. We will discuss the methodology and provide preliminary estimates of the branching fraction of $\bar{B}^0 \to D^{*+}\ell^- \bar \nu$ using the partial reconstruction technique.   

$B$ meson decays to $K_1(1270) \pi$ and $K_1(1400) \pi$

We present preliminary results of branching fraction measurements of $B^0$ meson decays to $K_1(1270)^+ \pi^-$ and $K_1(1400)^+ \pi^-$. The data sample corresponds to 384 million of $B \bar B$ pairs collected with the BaBar detector at the PEP II asymmetric energy $e^+ e^-$ collider.   

Measurement of the Lifetime of the $B_c^{\pm}$ Meson Using Semileptonic Decays

We report on a measurment of the lifetime of the $B_c^{\pm}$ meson using the semileptonic decay modes $B_c^{\pm} \rightarrow J/\psi \ell^{\pm} X$ with $J/\psi \rightarrow \mu^+ \mu^-$. The measurement utilizes 1~fb$^{-1}$ of data collected with the CDF\,II detector during Run\,II of the Fermilab Tevatron in $p\bar{p}$ collisions at $\sqrt{s} = 1.96$~TeV. The measurement combines the $J/\psi\mu^{\pm}$ and $J/\psi e^{\pm}$ final states in a single framework to increase the statistical reach of the data while minimizing systematic differences between the two final states.   

Angular Time-dependent Analyses of the Decays $B_d\rightarrow J/\psi K^{0*}$ and $B_s\rightarrow J/\psi\phi$ at D0

We report preliminary results on the $B_d$ untagged angular time-dependent analysis in the exclusive decay channel $B_d\rightarrow J/\psi (\rightarrow \mu^+\mu^-) K^{0*} (\rightarrow K^\pm\pi^\mp)$. We use approximately 2.8 fb$^{-1}$ of data collected at the D0 detector during 2003-2007. From our measurements we are able to measure the angular and the lifetime parameters ($|A_0|^2$, $|A_{\parallel}|^2$ $\delta_1$, $\delta_2$ and $\tau_d$) that describe this decay in the transversity basis. We performed the same analysis for the untagged decay $B_s\rightarrow J/\psi (\rightarrow \mu^+\mu^-) \phi (\rightarrow K^+K^-)$ assuming no CP violation, and measured the parameters $|A_0|^2$, $|A_{\parallel}|^2$ $\delta_2-\delta_1$, $\Delta \Gamma_s$ and $\tau_s$. Finally, we report the lifetime ratio $\tau_s/\tau_d=1.035\pm0.060\mathrm{(stat)}\pm0.004\mathrm {(syst)}$. We compare our measurements with the theoretical predictions for the factorization method and the SU(3) symmetry for these decays.   

$CP$~Violation in $B\rightarrow DK$ Decay Modes at CDF

The CKM angle $\gamma$ can be cleanly determined from $CP$~asymmetries in suppressed $B^+\rightarrow D^0 K^+$ decays, where it enters at tree-level. These measurements do not require flavor tagging and are currently statistics-limited, which makes them particularly interesting for hadron colliders. We present the latest CDF results for the submodes $D^0\rightarrow K^+K^-$, $\pi^+\pi^-$ ($CP+$ modes) and the DCS mode $D^0\rightarrow K^+\pi^-$.   

Same-Side Flavor-Tagging in $B_s$ Decays at D0

A same-side tagging method is applied to determine the $b/\bar{b}$-quark flavor of $B_s$-mesons at the time of production in proton-antiproton collisions. The performance of the method is determined using Monte Carlo techniques. The verification of the method is performed on real $B^\pm \to J/\psi K^\pm$ events and Monte Carlo samples. The same-side tagging method is combined with opposite-side tagging to take into account all the available information about initial $B_s$ meson flavor. The analysis serves as a foundation for application of the same-side tagging method to $B_s$-meson data samples.   

Rare B Decays at D0

Studies of the B meson system are motivated both by precise consistency tests of the standard model (SM) and for searching for indirect effects of new physics. In the SM flavour changing neutral currents (FCNC) are absent at tree level but appear in higher order diagrams through box and penguin diagrams. B meson decays involving such FCNC have branching ratios of order 10$^{-7}$ to 10$^{-6}$ in the SM, but are expected to be enhanced in many models beyond the SM. Investigations into some rare decays like $B \rightarrow X_s \mu \mu$ will be presented, using data taken by the D0 experiment at Fermilab.