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Register a new userMeasurement of the inclusive semileptonic branching fraction $mathcal{B}(B_s^0 rightarrow X^- ell^+ u_ell)$ at Belle
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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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Inclusive semileptonic B_s^0 -> X^+ l^- u decays are studied for the first time using a 23.6 fb^{-1} data sample collected on the Y(5S) resonance with the Belle detector at the KEKB asymmetric energy e^+ e^- collider. These decays are identified by the means of a lepton accompanied by a same-sign D_s^+ meson originating from the other B_s^0 in the event. The semileptonic branching fractions are measured in the electron and muon channels to be Bf(B_s^0 -> X^+ e^- u) = (10.9 pm 1.0 pm 0.9)% and Bf(B_s^0 -> X^+ mu^- u) = (9.2 pm 1.0 pm 0.8)%, respectively. Assuming an equal electron and muon production rate in B_s^0 decays, a combined fit yields an average leptonic branching fraction Bf(B_s^0 -> X^+ l^- u) = (10.2 pm 0.8 pm 0.9)%.
We report the first direct measurement of the inclusive branching fraction ${mathcal B}(B_s rightarrow D_s X)$ via $B_s$ tagging in $e^+e^-toUpsilon$(5S) events. Tagging is accomplished through a partial reconstruction of semileptonic decays $B_s rightarrow D_s X ell u$, where $X$ denotes unreconstructed additional hadrons or photons and $ell$ is an electron or muon. With 121.4 fb$^{-1}$ of data collected at the $Upsilon$(5S) resonance by the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider, we obtain ${mathcal B}(B_s rightarrow D_s X)$ = $(61.6 pm 5.3 pm 2.1)$%, where the first uncertainty is statistical and the second is systematic.
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.
We measure the branching fractions for the decays $bar{B}^0 to D^{*+} e^{-} bar{ u}_e$ and $bar{B}^0 to D^{*+} mu^{-} bar{ u}_mu$ using $8.70 pm 0.09~{rm fb}^{-1}$ of data collected by the Belle II experiment at the SuperKEKB asymmetric-energy $e^+ e^-$ collider. Candidate signal decays are reconstructed with the subsequent decays $D^{*+}to D^0 pi^+$ and $D^0to K^-pi^+$. We obtain the results ${cal B}(bar{B}^0 to D^{*+} e^{-} bar{ u}_e)$ = $(4.55pm0.14(mathrm{stat})pm0.35 (mathrm{syst})) %$ and ${cal B}(bar{B}^0 to D^{*+} mu^{-} bar{ u}_mu)$ = $(4.84pm 0.13(mathrm{stat})pm0.37(mathrm{syst})) %$, in agreement with the world averages. The measurements serve to validate the full chain of detector operation and calibration, data collection and processing, and production of physics results in the case of semileptonic $B$-meson decays.
We present a first measurement of the $bar{B^{0}} rightarrow D^{*+} ell^{-} u_{ell}$ branching fraction using fully reconstructed $B$ meson decays employing the Full Event Interpretation algorithm. Collision events corresponding to an integrated luminosity of lumi are analyzed, which were recorded by the Belle~II detector operated at the SuperKEKB accelerator complex. We measure$cal{B}(bar{B^{0}} rightarrow D^{*+} ell^{-} u_{ell}) =4.51 pm 0.41_{stat}pm0.27_{syst} pm0.45_{pi_s}$, with the first and second error denoting the statistical and systematic uncertainty, respectively, and the third dominant uncertainty is from the slow pion reconstruction efficiency.
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