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Register a new userMeasurement of the branching fraction and $CP$ asymmetry in $B^{0} to pi^{0}pi^{0}$ decays, and an improved constraint on $phi_{2}$
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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.
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We report a measurement of time-dependent $CP$ violation in $B^0 to K^0_S pi^0 pi^0$ decays using a data sample of $772 times 10^6$ $Bbar{B}$ pairs collected by the Belle experiment runnin g at the $Upsilon (4S)$ resonance at the KEKB $e^+ e^-$ collider. This decay proceeds mainly via a $bto sdbar{d}$ penguin amplitude. The results are $sin 2phi^{rm eff}_1 = 0.92^{+0.27}_{-0.31}~$ (stat.) $pm 0.11$ (syst.) and $mathcal{A} = 0.28 pm 0.21$ (stat.) $pm 0.04$ (syst.), which are the most precise measurements of $CP$ violati on in this decay mode to date. The value for the $CP$-violating parameter $sin 2phi^{rm eff}_1$ is consistent with that obtained using decay modes proceeding via a $bto cbar{c}s$ tree amplitude.
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.
An analysis of $B^+ to K_{rm scriptscriptstyle S}^0 pi^+$ and $B^+ to K_{rm scriptscriptstyle S}^0 K^+$ decays is performed with the LHCb experiment. The $pp$ collision data used correspond to integrated luminosities of $1{,fb}^{-1}$ and $2{,fb}^{-1}$ collected at centre-of-mass energies of $sqrt{s}=7mathrm{,Tekern -0.1em V}$ and $sqrt{s}=8mathrm{,Tekern -0.1em V}$, respectively. The ratio of branching fractions and the direct {it CP} asymmetries are measured to be $mathcal{B}(B^+ to K_{rm scriptscriptstyle S}^0 K^+)/mathcal{B}(B^+ to K_{rm scriptscriptstyle S}^0 pi^+) = 0.064 pm 0.009textrm{(stat.)} pm 0.004textrm{(syst.)}$, $mathcal{A}^{it CP}(B^+ to K_{rm scriptscriptstyle S}^0 pi^+) = -0.022 pm 0.025textrm{(stat.)} pm 0.010textrm{(syst.)}$ and $mathcal{A}^{it CP}(B^+ to K_{rm scriptscriptstyle S}^0 K^+) = -0.21 pm 0.14textrm{(stat.)} pm 0.01textrm{(syst.)}$. The data sample taken at $sqrt{s}=7mathrm{,Tekern -0.1em V}$ is used to search for $B_c^+ to K_{rm scriptscriptstyle S}^0 K^+$ decays and results in the upper limit $(f_ccdotmathcal{B}(B_c^+ to K_{rm scriptscriptstyle S}^0 K^+))/(f_ucdotmathcal{B}(B^+ to K_{rm scriptscriptstyle S}^0 pi^+)) < 5.8times10^{-2}textrm{at 90% confidence level}$, where $f_c$ and $f_u$ denote the hadronisation fractions of a $bar{b}$ quark into a $B_c^+$ or a $B^+$ meson, respectively.
Time-integrated $CP$ asymmetries in $D^0$ decays to the final states $K^- K^+$ and $pi^- pi^+$ are measured using proton-proton collisions corresponding to $3mathrm{,fb}^{-1}$ of integrated luminosity collected at centre-of-mass energies of $7mathrm{,Tekern -0.1em V}$ and $8mathrm{,Tekern -0.1em V}$. The $D^0$ mesons are produced in semileptonic $b$-hadron decays, where the charge of the accompanying muon is used to determine the initial flavour of the charm meson. The difference in $CP$ asymmetries between the two final states is measured to be begin{align} Delta A_{CP} = A_{CP}(K^-K^+)-A_{CP}(pi^-pi^+) = (+0.14 pm 0.16mathrm{,(stat)} pm 0.08mathrm{,(syst)})% . onumber end{align} A measurement of $A_{CP}(K^-K^+)$ is obtained assuming negligible $CP$ violation in charm mixing and in Cabibbo-favoured $D$ decays. It is found to be begin{align} A_{CP}(K^-K^+) = (-0.06 pm 0.15mathrm{,(stat)} pm 0.10mathrm{,(syst)}) % , onumber end{align} where the correlation coefficient between $Delta A_{CP}$ and $A_{CP}(K^-K^+)$ is $rho=0.28$. By combining these results, the $CP$ asymmetry in the $D^0rightarrowpi^-pi^+$ channel is $A_{CP}(pi^-pi^+)=(-0.20pm0.19mathrm{,(stat)}pm0.10mathrm{,(syst)})%$.
We report the measurement of the branching fraction and $CP$ asymmetry for the $bar{B}^{0}(B^{0})to K^{0}_{S}K^{mp}pi^{pm}$ decay. The analysis is performed on a data sample of 711 $rm{fb}^{-1}$ collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. We obtain a branching fraction of $(3.60pm0.33pm0.15)times10^{-6}$ and an $mathcal{A}_{CP}$ of $(-8.5pm8.9pm0.2)%$, where the first uncertainties are statistical and the second are systematic. Hints of peaking structures are also observed in the differential branching fraction as functions of Dalitz variables.
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