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Register a new userMeasurement of the time-integrated mixing probability $chi_d$ with a semileptonic double-tagging strategy and $34.6 {rm fb}^{-1}$ of Belle II collision data
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We present the first measurement of the time-integrated mixing probability $chi_d$ using Belle II data collected at a center-of-mass (CM) energy of 10.58 GeV, corresponding to the mass of the $Upsilon$(4S) resonance, with an integrated luminosity of $34.6 {rm fb}^{-1}$ at the SuperKEKB $e^+ e^-$ collider. We reconstruct pairs of B mesons both of which decay to semileptonic final states. Using a novel methodology, we measure $chi_d = 0.187 pm 0.010 text{ (stat.)} pm 0.019 text{ (syst.)}$, which is compatible with existing indirect and direct determinations.
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We present the results of the re-discovery of the decay $B^0 to pi^- ell^+ u_ell$ in 34.6 fb$^{-1}$ of Belle II data using hadronic $B$-tagging via the Full Event Interpretation algorithm. We observe 21 signal events on a background of 155 in a fit to the distribution of the square of the missing mass, $M_{mathrm{miss}}^2$, with a significance of 5.69$sigma$, and determine a total branching fraction of (1.58 $pm$ 0.43$_{mathrm{stat}}$ $pm$ 0.07$_{mathrm{sys}}$) $times 10^{-4}$.
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 measurements of the $bar{B}^0 to D^{*+} ell^{-} bar{ u}_l$ and $B^- to D^{0} ell^{-} bar{ u}_l$ processes using 34.6 fb$^{-1}$ of collision events recorded by the Belle II experiment at the SuperKEKB asymmetric-energy $e^+ e^-$ collider. For the $B^-to D^{0}ell^-bar u_ell$ channel, we present first studies that isolate this decay from other semileptonic processes and backgrounds. We report a measurement of the $bar{B}^0 to D^{*+} ell^{-} bar{ u}_l$ branching fraction and obtain ${cal B}(bar{B}^0 to D^{*+} ell^{-} bar{ u}_l) = left(4.60 pm 0.05_{mathrm{stat}}pm0.17_{mathrm{syst}} pm 0.45_{pi_s}right) %$, in agreement with the world average. Here, the uncertainties are statistical, systematic, and related to slow pion reconstruction, respectively. The systematic uncertainties are limited by the statistics of auxiliary measurements and will improve in the future. We also report differential branching fractions in five bins of the hadronic recoil parameter $w$ for $bar{B}^0 to D^{*+} ell^{-} bar{ u}_l$, unfolded to account for resolution and efficiency effects.
We report measurements related to hadronic $B$ decays to final states that contain charm mesons. The analyses are performed on a $62.8~mathrm{fb}^{-1}$ data set collected by the Belle II experiment at a center-of-mass energy corresponding to the mass of the $Upsilon(4S)$ resonance. The measurements reported are for the decay modes $B^-to D^0 h^-$, $B^{-}to D^{*0}h^-$, $bar{B}^{0}to D^{+} h^{-}$ and $bar{B}^{0}to D^{*+} h^{-}$, where $h=pi$ or $K$. These modes are either signal or control channels for measurements related to the unitarity triangle angle $gamma$ in direct or time-dependent $CP$-violation measurements. The reported observables are the ratios between the $Bto D^{(*)}K$ and $Bto D^{(*)}pi$ decay rates, which are found to be in agreement with previous measurements.
We report a measurement of the branching fraction of $B^+ to tau^+ u_tau$ decays using a data sample of $772 times 10^6 B bar{B}$ pairs, collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. We reconstruct the accompanying $B$ meson in a semileptonic decay and detect the $B^+ to tau^+ u_tau$ candidate in the recoiling event. We obtain a branching fraction of ${cal B}(B^+ to tau^+ u_tau) = [1.25 pm 0.28 ({rm stat.}) pm 0.27({rm syst.})] times 10^{-4}$. This result is in good agreement with previous measurements and the expectation from calculations based on the Standard Model.
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