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Register a new userMeasurement of the branching fraction of $B rightarrow D^{(*)}pi ell u$ at Belle using hadronic tagging in fully reconstructed events
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We report a measurement of the branching fraction of the decay $B rightarrow D^{(*)}pi ell u$. The analysis uses 772$times 10^6$ $Bbar{B}$ pairs produced in $e^+e^-rightarrow Upsilon(4S)$ data recorded by the Belle experiment at the KEKB asymmetric-energy $e^+e^-$ collider. The tagging $B$ meson in the decay is fully reconstructed in a hadronic decay mode. On the signal side, we reconstruct the decay $B rightarrow D^{(*)}pi ell u$ $(ell=e,mu)$. The measured branching fractions are $mathcal{B}(B^+ rightarrow D^-pi^+ ell^+ u)$ = [4.55 $pm$ 0.27 (stat.) $pm$ 0.39 (syst.)]$times 10^{-3}$, $mathcal{B}(B^0 rightarrow bar{D}^0pi^- ell^+ u)$ = [4.05 $pm$ 0.36 (stat.) $pm$ 0.41 (syst.)]$times 10^{-3}$, $mathcal{B}(B^+ rightarrow D^{*-}pi^+ ell^+ u)$ = [6.03 $pm$ 0.43 (stat.) $pm$ 0.38 (syst.)]$times 10^{-3}$, and $mathcal{B}(B^0 rightarrow bar{D}^{*0}pi^- ell^+ u)$ = [6.46 $pm$ 0.53 (stat.) $pm$ 0.52 (syst.)]$times 10^{-3}$. These are in good agreement with the current world average values.
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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.
We report the first reconstruction of the $B^{0} to pi^{0} pi^{0}$ decay mode at Belle II using samples of 2019 and 2020 data that correspond to 62.8 fb$^{-1}$ of integrated luminosity. We find $14.0^{+6.8}_{-5.6}$ signal decays, corresponding to a significance of 3.4 standard deviations and determine a branching ratio of $mathcal{B}(B^{0} rightarrow pi^{0} pi^{0}) = [0.98^{+0.48}_{-0.39} pm 0.27] times 10^{-6}$. The results agree with previous determinations and contribute important information to an early assessment of detector performance and Belle IIs potential for future determinations of $alpha/phi_2$ using $B rightarrow pi pi$ modes.
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.
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 $[9.6 pm 0.4text{(stat)} pm 0.7text{(syst)}]~%$.
We report a measurement of the branching fraction ratios R(D(*)) of Bbar -> D(*) tau- nubar_tau relative to Bbar -> D()* l- nubar_l (where l = e or mu) using the full Belle data sample of 772 x 10^6 BBbar pairs collected at the Y(4S) resonance with the Belle detector at the KEKB asymmetric-energy e+e- collider. The measured values are R(D)= 0.375 +- 0.064(stat.) +- 0.026(syst.) and R(D*) = 0.293 +- 0.038(stat.) +- 0.015(syst.). The analysis uses hadronic reconstruction of the tag-side B meson and purely leptonic tau decays. The results are consistent with earlier measurements and do not show a significant deviation from the standard model prediction.
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