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Register a new userMeasurement of the branching fraction for $B^{0} rightarrow pi^{0} pi^{0}$ decays reconstructed in 2019-2020 Belle II data
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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.
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We report measurements of branching fractions ($mathcal B$) and direct ${it CP}$-violating asymmetries ($mathcal A_{it CP}$) for the decays $B^+to K^+pi^0$ and $B^+ to pi^+pi^0$ reconstructed with the Belle II detector in a sample of asymmetric-energy electron-positron collisions at the $Upsilon(4S)$ resonance corresponding to 62.8 $text{fb}^{-1}$ of integrated luminosity. The results are $mathcal{B}(B^+ to K^+pi^0) = [11.9 ^{+1.1}_{-1.0} (rm stat)pm 1.6(rm syst)]times 10^{-6}$, $mathcal{B}(B^+ to pi^+pi^0) = [5.5 ^{+1.0}_{-0.9} (rm stat)pm 0.7(rm syst)]times 10^{-6}$, $mathcal A_{it CP}(B^+ to K^+pi^0) = -0.09 pm 0.09 (rm stat)pm 0.03(rm syst)$, and $mathcal A_{it CP}(B^+ to pi^+pi^0) = -0.04 pm 0.17 (rm stat)pm 0.06(rm syst)$. The results are consistent with previous measurements and show a detector performance comparable with early Belle performance.
We report measurements of the branching fractions and $CP$ asymmetries for $D_s^{+} rightarrow K^{+} eta $, $D_s^{+} rightarrow K^{+} pi^0 $, and $D_s^{+} rightarrow pi^{+} eta $ decays, and the branching fraction for $D_s^{+} rightarrow pi^{+} pi^0$. Our results are based on a data sample corresponding to an integrated luminosity of 921 fb$^{-1}$ collected by the Belle detector at the KEKB $e^+e^-$ asymmetric-energy collider. Our measurements of $CP$ asymmetries in these decays are the most precise to-date; no evidence for $CP$ violation is found.
A branching fraction measurement of the $B^{0}rightarrow D_{s}^{+}pi^{-}$ decay is presented using proton-proton collision data collected with the LHCb experiment, corresponding to an integrated luminosity of $5.0,$fb$^{-1}$. The branching fraction is found to be ${mathcal{B}(B^{0}rightarrow D_{s}^{+}pi^{-}) = (19.4 pm 1.8pm 1.3 pm 1.2)times 10^{-6}}$, where the first uncertainty is statistical, the second systematic and the third is due to the uncertainty on the $B^0 to D^{-}pi^{+}$, $D_{s}^{+}rightarrow K^{+}K^{-}pi^{+}$ and $D^{-}rightarrow K^{+}pi^{-}pi^{-}$ branching fractions. This is the most precise single measurement of this quantity to date. As this decay proceeds through a single amplitude involving a $b to u$ charged-current transition, the result provides information on non-factorisable strong interaction effects and the magnitude of the Cabibbo-Kobayashi-Maskawa matrix element $V_{ub}$. Additionally, the collision energy dependence of the hadronisation-fraction ratio $f_s/f_d$ is measured through $bar{B}{}_{s}^{0}rightarrow D_{s}^{+}pi^{-}$ and $B^0 to D^{-}pi^{+}$ decays.
We measure the branching fraction and $CP$ violation asymmetry in the decay $B^{0}to pi^{0}pi^{0}$, using a data sample of $752times 10^{6}$ $Bbar{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB $e^{+}e^{-}$ collider. The obtained branching fraction and direct $CP$ asymmetry are $ mathcal{B}(Bto pi^{0}pi^{0}) = [1.31 pm 0.19~ text{(stat.)} pm 0.19~ text{(syst.)}] times 10^{-6}$ and $ A_{CP} = +0.14 pm 0.36~ text{(stat.)} pm 0.10~ text{(syst.)}, $ respectively. The signal significance, including the systematic uncertainty, is 6.4 standard deviations. We combine these results with Belles earlier measurements of $B^{0}to pi^{+} pi^{-}$ and $B^{pm} to pi^{pm} pi^{0}$ to exclude the $CP$-violating parameter $phi_{2}$ from the range $15.5^{circ} < phi_{2} < 75.0^{circ}$ at 95% confidence level.
A measurement of the differential branching fraction of the decay ${B^{0}rightarrow K^{ast}(892)^{0}mu^{+}mu^{-}}$ is presented together with a determination of the S-wave fraction of the $K^+pi^-$ system in the decay $B^{0}rightarrow K^{+}pi^{-}mu^{+}mu^{-}$. The analysis is based on $pp$-collision data corresponding to an integrated luminosity of 3,fb$^{-1}$ collected with the LHCb experiment. The measurements are made in bins of the invariant mass squared of the dimuon system, $q^2$. Precise theoretical predictions for the differential branching fraction of $B^{0}rightarrow K^{ast}(892)^{0}mu^{+}mu^{-}$ decays are available for the $q^2$ region $1.1<q^2<6.0,{rm GeV}^2/c^4$. In this $q^2$ region, for the $K^+pi^-$ invariant mass range $796 < m_{Kpi} < 996,{rm MeV}/c^2$, the S-wave fraction of the $K^+pi^-$ system in $B^{0}rightarrow K^{+}pi^{-}mu^{+}mu^{-}$ decays is found to be begin{equation*} F_{rm S} = 0.101pm0.017({rm stat})pm0.009 ({rm syst}), end{equation*} and the differential branching fraction of $B^{0}rightarrow K^{ast}(892)^{0}mu^{+}mu^{-}$ decays is determined to be begin{equation*} {rm d}mathcal{B}/{rm d} q^2 = (0.342_{,-0.017}^{,+0.017}({rm stat})pm{0.009}({rm syst})pm0.023({rm norm}))times 10^{-7}c^{4}/{rm GeV}^{2}. end{equation*} The differential branching fraction measurements presented are the most precise to date and are found to be in agreement with Standard Model predictions.
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