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Register a new userMeasurement of branching fraction and direct $CP$ asymmetry in charmless $B^+ to K^+K^- pi^+$ decays at Belle
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We report a study of the charmless hadronic decay of the charged $B$ meson to the three-body final state $K^+ K^- pi^+$. The results are based on a data sample that contains $772times10^6$ $B bar{B}$ pairs collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+ e^-$ collider. The measured inclusive branching fraction and the direct $CP$ asymmetry are $(5.38pm0.40pm0.35)times 10^{-6}$ and $-0.170pm0.073pm0.017$, respectively, where the first uncertainties are statistical and the second are systematic. The $K^{+}K^{-}$ invariant mass distribution of the signal candidates shows an excess in the region below $1.5$ GeV/$c^2$, which is consistent with the previous studies from BaBar and LHCb. In addition, strong evidence of a large direct $CP$ asymmetry is found in the $K^{+}K^{-}$ low-invariant-mass region.
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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.
We report on the first measurement of the direct $CP$-violating asymmetry ($mathcal{A}$) in the charmless decay $B^0 to K^0pi^0$ at Belle II and an updated measurement of its branching fraction ($mathcal{B}$). We use a sample of electron-positron collisions collected in 2019 and 2020 at the $Upsilon(4S)$ resonance and corresponding to $62.8$ $text{fb}^{-1}$ of integrated luminosity. We reconstruct and select about $50$ $B^0 to K_S^0 pi^0$ candidates, and we measure $mathcal{A}_{{K^0pi^0}} = -0.40_{-0.44}^{+0.46} (text{stat}) pm 0.04 (text{syst})$ and $mathcal{B}(B^0 to K^0 pi^0) = [8.5_{-1.6}^{+1.7} (text{stat}) pm 1.2 (text{syst})] times 10^{-6}$. This is the first measurement of $CP$ violation in $B^0 to K^0pi^0$ decays reported by Belle II. The results agree with previous determinations and show a detector performance comparable with the best Belle results.
We report measurements of the branching fractions and direct CP asymmetries (A_{CP}) for B->K pi, pi pi and KK decays (but not pi^0 pi^0) based on the final data sample of 772x10^6 B B-bar pairs collected at the Upsilon(4S) resonance with the Belle detector at the KEKB asymmetric-energy e^+ e^- collider. We set a 90% confidence-level upper limit for K^+- K^-+ at 2.0x10^{-7}; all other decays are observed with branching fractions ranging from 10^{-6} to 10^{-5}. In the $B^0/B^0-bar -> K^+-pi^-+ mode, we confirm Belles previously reported large A_{CP} with a value of -0.069 +- 0.014 +- 0.007 and a significance of 4.4 sigma. For all other flavor-specific modes, we find A_{CP} values consistent with zero, including A_{CP}(K^+- pi^0) = +0.043 +- 0.024 +- 0.007 with 1.8 sigma significance. The difference of CP asymmetry between B^+- -> K^+- pi^0 and B^0/B^0-bar -> K^+-pi^-+ is found to be Delta A_{K pi} equiv A_{CP} (K^+ pi^0) - A_{CP}(K^+ pi^-) = +0.112 +- 0.027 +- 0.007 with 4.0 sigma significance. We also calculate the ratios of partial widths for the B-> K pi decays. Using our results, we test the validity of the sum rule A_{CP}(K^+ pi^-) + A_{CP}(K^0pi^+) x Gamma(K^0pi^+)/Gamma(K^+ pi^-)} - A_{CP}(K^+ pi^0)x 2Gamma(K^+ pi^0)/Gamma(K^+ pi^-) - A_{CP}(K^0 pi^0)x 2Gamma(K^0 pi^0)/Gamma(K^+ pi^-) = 0 and obtain a sum of -0.270 +- 0.132 +- 0.060 with 1.9 sigma significance.
We report a search for charmless hadronic decays of charged $B$ mesons to the final states $K^{0}_{S} K^{0}_{S} K^{pm}$ and $K^{0}_{S} K^{0}_{S} pi^{pm}$ . The results are based on a $711 {fb}^{-1}$ data sample that contains $772 times 10^6$ $B bar{B}$ pairs, and was collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^{+}e^{-}$ collider. For $B^{pm} to K^{0}_{S} K^{0}_{S} K^{pm}$ decays, the measured branching fraction and direct $CP$ asymmetry are $[10.64pm0.49(stat)pm 0.44(syst)]times10^{-6}$ and [$-0.6pm3.9(stat)pm 3.4(syst)$] %, respectively. In the absence of a statistically significant signal for $B^{pm}to K^{0}_{S} K^{0}_{S} pi^{pm}$, we set the 90 % confidence-level upper limit on its branching fraction at $1.14 times 10^{-6}$.
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.
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