A. Pompili

We present updated measurements of the branching fractions and $CP$ asymmetries for $B^0\to {\pi }^0{\pi }^0$, $B^{\pm }\to {\pi }^{\pm }{\pi }^0$, and $B^{\pm }\to K^{\pm }{\pi }^0$. Based on a sample of $383\times {10}^6$ $\mathit{{\rm Y}}(4S)\to B\overline{B}$ decays collected by the BABAR detector at the PEP-II asymmetric-energy $B$ factory at SLAC, we measure $\mathcal{B}(B^0\to {\pi }^0{\pi }^0)=(1.47\pm 0.25\pm 0.12)\times {10}^{-6}$, $\mathcal{B}(B^{\pm }\to {\pi }^{\pm }{\pi }^0)=(5.02\pm 0.46\pm 0.29)\times {10}^{-6}$, and $\mathcal{B}(B^{\pm }\to K^{\pm }{\pi }^0)=(13.6\pm 0.6\pm 0.7)\times {10}^{-6}$. We also measure the $CP$ asymmetries ${\mathcal{C}}_{{\pi }^0{\pi }^0}=-0.49\pm 0.35\pm 0.05$, ${\mathcal{A}}_{{\pi }^{\pm }{\pi }^0}=0.03\pm 0.08\pm 0.01$, and ${\mathcal{A}}_{K^{\pm }{\pi }^0}=0.030\pm 0.039\pm 0.010$. Finally, we present bounds on the Cabibbo-Kobayashi-Maskawa angle $\alpha$ using isospin relations.

We report the observation of the decay $B^{-}\to D_{{\pi }^{+}{\pi }^{-}{\pi }^0}{K}^{-}$, where $D_{{\pi }^{+}{\pi }^{-}{\pi }^0}$ indicates a neutral $D$ meson detected in the final state ${\pi }^{+}{\pi }^{-}{\pi }^0$, excluding $K_S^0{\pi }^0$. This doubly Cabibbo-suppressed decay chain can be used to measure the CKM phase $\gamma$. Using about $229\times {10}^6$ $e^{+}{e}^{-}\to B\overline{B}$ events recorded by the BABAR experiment at the PEP-II $e^{+}{e}^{-}$ storage ring, we measure the branching fraction $\mathcal{B}(B^{-}\to D_{{\pi }^{+}{\pi }^{-}{\pi }^0}{K}^{-})=(5.5\pm 1.0(\mathrm{stat}.)\pm 0.7(\mathrm{syst}.))\times {10}^{-6}$ and the decay rate asymmetry $A(B^{-}\to D_{{\pi }^{+}{\pi }^{-}{\pi }^0}{K}^{-})=-0.02\pm 0.16(\mathrm{stat}.)\pm 0.03(\mathrm{syst}.)$ for the full decay chain.

The branching fraction of the ${\tau }^{-}\to 3h^{-}2h^{+}{\nu }_{\tau }$ decay ($h=\pi ,K$) is measured with the BABAR detector to be $(8.56\pm 0.05\pm 0.42)\times {10}^{-4}$, where the first error is statistical and the second systematic. The observed structure of this decay is significantly different from the phase space prediction, with the $\rho$ resonance playing a strong role. The decay ${\tau }^{-}\to f_1(1285){\pi }^{-}{\nu }_{\tau }$, with the $f_1(1285)$ meson decaying to four charged pions, is observed and the branching fraction is measured to be $(3.9\pm 0.7\pm 0.5)\times {10}^{-4}$.

We report on a search for the rare decay ${\overline{B}}^0\to D^{*0}\gamma$, which in the standard model is dominated by $W$-exchange. The analysis is based on a data sample comprising $87.8\times {10}^6$ $B\overline{B}$ pairs collected with the BABAR detector at the PEP-II asymmetric-energy $B$ Factory at SLAC. No significant signal is observed, and an upper limit on the branching fraction of $2.5\times {10}^{-5}$ at the 90% confidence level is obtained.

A Dalitz plot analysis of approximately 12 500 $D^0$ events reconstructed in the hadronic decay $D^0\to {\overline{K}}^0{K}^{+}{K}^{-}$ is presented. This analysis is based on a data sample of $91.5{\mathrm{fb}}^{-1}$ collected with the BABAR detector at the PEP-II asymmetric-energy $e^{+}{e}^{-}$ storage rings at SLAC running at center-of-mass energies on and 40 MeV below the ${\rm Y}(4S)$ resonance. The events are selected from $e^{+}{e}^{-}\to c\overline{c}$ annihilations using the decay $D^{*+}\to D^0{\pi }^{+}$. The following ratio of branching fractions has been obtained: $BR=\frac{\Gamma (D^0\to {\overline{K}}^0{K}^{+}{K}^{-})}{\Gamma (D^0\to {\overline{K}}^0{\pi }^{+}{\pi }^{-})}=(15.8\pm 0.1(\mathrm{stat}.)\pm 0.5(\mathrm{syst}.))\times {10}^{-2}.$ Estimates of fractions and phases for resonant and nonresonant contributions to the Dalitz plot are also presented. The $a_0(980)\to \overline{K}K$ projection has been extracted with little background. A search for $CP$ asymmetries on the Dalitz plot has been performed.

We report on the search for the rare decays $B^{+}\to D^{(*)+}{K}_S^0$ in approximately $226\times {10}^6$ ${\rm Y}(4S)\to B\overline{B}$ decays collected with the BABAR detector at the PEP-II asymmetric-energy $B$ factory at SLAC. We do not observe any significant signal and we set 90% confidence-level upper limits on the branching fractions, $\mathcal{B}(B^{+}\to D^{+}{K}^0)<0.5\times {10}^{-5}$ and $\mathcal{B}(B^{+}\to D^{*+}{K}^0)<0.9\times {10}^{-5}$.

We report a search for $B\to J/\psi D$ decays, based on a sample of $124\times {10}^6$ $B\overline{B}$ events collected with the BABAR detector at the PEP-II storage ring of the Stanford Linear Accelerator Center. No significant signal is found. We obtain upper limits on the branching fractions of $1.3\times {10}^{-5}$ for $B^0\to J/\psi {\overline{D}}^0$ and $1.2\times {10}^{-4}$ for $B^{+}\to J/\psi D^{+}$ at 90% confidence level.

We measure the time-dependent $CP$ asymmetry parameters in $B^0\to K^{+}{K}^{-}{K}^0$ based on a data sample of approximately $227\times {10}^6$ $B$-meson pairs recorded at the ${\rm Y}(4S)$ resonance with the BABAR detector at the PEP-II $B$-meson Factory at SLAC. We reconstruct two-body $B^0$ decays to $\varphi (1020)K_S^0$ and $\varphi (1020)K_L^0$, and the three-body decay $K^{+}{K}^{-}{K}_S^0$ with $\varphi (1020)K_S^0$ excluded. For the $B^0\to \varphi K^0$ decays, we measure $\sin 2{\beta }_{\mathrm{eff}}(\varphi K^0)=+0.50\pm 0.25(\mathrm{stat}{)}_{-0.04}^{+0.07}(\mathrm{syst})$. The $B^0\to K^{+}{K}^{-}{K}_S^0$ decays are dominated by $K^{+}{K}^{-}$ $S$ wave, as determined from an angular analysis; we measure $\sin 2{\beta }_{\mathrm{eff}}(K^{+}{K}^{-}{K}_S^0)=+0.55\pm 0.22(\mathrm{stat})\pm 0.04(\mathrm{syst})\pm 0.11(CP)$, where the last error is due to the uncertainty in the fraction of $CP$-even contributions to the decay amplitude. We find no evidence for direct $CP$ violation.