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Register a new userMeasurement of the Decays $boldsymbol{Btoetaell u_ell}$ and $boldsymbol{Btoeta^primeell u_ell}$ in Fully Reconstructed Events at Belle
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We report branching fraction measurements of the decays $B^+toetaell^+ u_ell$ and $B^+toeta^primeell^+ u_ell$ based on 711~fb$^{-1}$ of data collected near the $Upsilon(4S)$ resonance with the Belle experiment at the KEKB asymmetric-energy $e^+e^-$ collider. This data sample contains 772 million $Bbar B$~events. One of the two $B$~mesons is fully reconstructed in a hadronic decay mode. Among the remaining (signal-$B$) daughters, we search for the $eta$~meson in two decay channels, $etatogammagamma$ and $etatopi^+pi^-pi^0$, and reconstruct the $eta^{prime}$~meson in $eta^primetoetapi^+pi^-$ with subsequent decay of the $eta$ into $gammagamma$. Combining the two $eta$ modes and using an extended maximum likelihood, the $B^+toetaell^+ u_ell$ branching fraction is measured to be $(4.2pm 1.1 (rm stat.)pm 0.3 (rm syst.))times 10^{-5}$. For $B^+toeta^primeell^+ u_ell$, we observe no significant signal and set an upper limit of $0.72times 10^{-4}$ at 90% confidence level.
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We present an analysis of the exclusive $B^{+}topi^{+}pi^{-}ell^{+} u_{ell}$ decay, where $ell$ represents an electron or a muon, with the assumption of charge-conjugation symmetry and lepton universality. The analysis uses the full $Upsilon(4S)$ data sample collected by the Belle detector, corresponding to 711 fb$^{-1}$ of integrated luminosity. We select the events by fully reconstructing one $B$ meson in hadronic decay modes, subsequently determining the properties of the other $B$ meson. We extract the signal yields using a binned maximum-likelihood fit to the missing-mass squared distribution in bins of the invariant mass of the two pions or the momentum transfer squared. We measure a total branching fraction of ${{cal B}(B^{+}to pi^{+}pi^{-}ell^{+} u_{ell})= [22.7 ^{+1.9}_{-1.6} (mathrm{stat}) pm 3.5(mathrm{syst}) ]times 10^{-5}}$, where the uncertainties are statistical and systematic, respectively. This result is the first reported measurement of this decay.
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We present the results of a search for the rare decays $Bto h uoverline{ u}$, where $h$ stands for $K^+,:K^0_{mathrm{S}},:K^{ast +},:K^{ast 0},:pi^+,:pi^0,:rho^+$ and $rho^{0}$. The results are obtained with $772times10^{6}$ $Boverline{B}$ pairs collected with the Belle detector at the KEKB $e^+ e^-$ collider. We reconstruct one $B$ meson in a semileptonic decay and require a single $h$ meson but nothing else on the signal side. We observe no significant signal and set upper limits on the branching fractions. The limits set on the $Bto K^0_{mathrm{S}} uoverline{ u}$, $B^0to K^{*0} uoverline{ u}$, $Bto pi^+ uoverline{ u}$, $B^0topi^0 uoverline{ u}$, $B^+torho^+ uoverline{ u}$, and $B^0torho^0 uoverline{ u}$ channels are the worlds most stringent.
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We report a measurement of the inclusive semileptonic $B_s^0$ branching fraction in a $121~fb^{-1}$ data sample collected near the $Upsilon(5S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+ e^-$ collider. Events containing $B_s^0$ pairs are selected by reconstructing a tag side $D_s^+$ and identifying a signal side lepton $ell^+$ ($ell = e, mu$) that is required to have the same-sign charge to ensure that both originate from different $B_s^0$ mesons. The $B_s^0 rightarrow X^- ell^+ u_ell$ branching fraction is extracted from the ratio of the measured yields of $D_s^+$ mesons and $D_s^+ ell^+$ pairs and the known production and branching fractions. The inclusive semileptonic branching fraction is measured to be $[9.6 pm 0.4text{(stat)} pm 0.7text{(syst)}]~%$.
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