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Register a new userMeasurements of Branching Fractions and Direct CP Asymmetries for B -> K pi, B->pi pi and B->to KK Decays
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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 $B^0/B^0-bar -> K^+-pi^-+ mode, we confirm Belles previously reported large A_{CP} with a value of -0.069 +- 0.014 +- 0.007 and a significance of 4.4 sigma. For all other flavor-specific modes, we find A_{CP} values consistent with zero, including A_{CP}(K^+- pi^0) = +0.043 +- 0.024 +- 0.007 with 1.8 sigma significance. The difference of CP asymmetry between B^+- -> K^+- pi^0 and B^0/B^0-bar -> K^+-pi^-+ is found to be Delta A_{K pi} equiv A_{CP} (K^+ pi^0) - A_{CP}(K^+ pi^-) = +0.112 +- 0.027 +- 0.007 with 4.0 sigma significance. We also calculate the ratios of partial widths for the B-> K pi decays. Using our results, we test the validity of the sum rule A_{CP}(K^+ pi^-) + A_{CP}(K^0pi^+) x Gamma(K^0pi^+)/Gamma(K^+ pi^-)} - A_{CP}(K^+ pi^0)x 2Gamma(K^+ pi^0)/Gamma(K^+ pi^-) - A_{CP}(K^0 pi^0)x 2Gamma(K^0 pi^0)/Gamma(K^+ pi^-) = 0 and obtain a sum of -0.270 +- 0.132 +- 0.060 with 1.9 sigma significance.
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A study of B+ to J/psi pi+ and B+ to psi(2S) pi+ decays is performed with data corresponding to 0.37 fb-1 of proton-proton collisions at sqrt(s)=7 TeV. Their branching fractions are found to be B(B+ to J/psi pi+) = (3.88 +- 0.11 +- 0.15) x 10^{-5} and B(B+ to psi(2S) pi+) = (2.52 +- 0.26 +- 0.15) x 10^{-5}, where the first uncertainty is related to the statistical size of the sample and the second quantifies systematic effects. The measured CP asymmetries in these modes are ACP(J/psi pi) = 0.005 +- 0.027 +- 0.011 and ACP(psi(2S) pi) = 0.048 +- 0.090 +- 0.011 with no evidence of direct CP violation seen.
We report updated measurements of branching fractions ($mathcal{B}$) and CP-violating charge asymmetries ($mathcal{A_{rm CP}}$) for charmless $B$ decays at Belle II, which operates on or near the $Upsilon$(4S) resonance at the SuperKEKB asymmetric energy $e^{+}e^{-}$ collider. We use samples of 2019 and 2020 data corresponding to 62.8 fb$^{-1}$ of integrated luminosity. The samples are analysed using two-dimensional fits in $Delta E$ and $M_{it bc}$ to determine signal yields of approximately 568, 103, and 115 decays for the channels $B^0 to K^+pi^-$, $B^+ to K_{rm S}^0pi^+$, and $B^0 to pi^+pi^-$, respectively. Signal yields are corrected for efficiencies determined from simulation and control data samples to obtain branching fractions and CP-violating asymmetries for flavour-specific channels. The results are compatible with known determinations and contribute important information to an early assessment of Belle II detector performance.
We present updated measurements of branching fractions and CP-violating asymmetries for neutral B meson decays to two-body final states of charged pions and kaons. The results are obtained from a data sample of about 60 million Y(4S) --> B-anti-B decays collected between 1999 and 2001 by the BABAR detector at the PEP-II asymmetric-energy B Factory at SLAC. The sample contains 124^{+16}_{-15} pi-pi, 403+/-24 K-pi, and 0.6^{+8.0}_{-7.4} K-K candidates, from which we measure the following quantities: BF(B0 --> pi+pi-) = (5.4+/-0.7+/-0.4) x 10^{-6}, BF(B0 --> K+pi-) = (17.8+/-1.1+/-0.8) x 10^{-6}, BF(B0 --> K+K-) < 1.1 x 10^{-6} (90% C.L.} A_Kpi = -0.05+/-0.06+/-0.01 [-0.14,+0.05], S_pipi = -0.01+/-0.37+/-0.07 [-0.66,+0.62], C_pipi = -0.02+/-0.29+/-0.07 [-0.54,+0.48], where the errors are statistical and systematic, respectively, and the asymmetry limits correspond to the 90% confidence level. These results are preliminary.
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 investigate a possibility of observing CP asymmetries in the partial widths for the decays B^- -> pi^+ pi^- K^- and B^- -> K^+ K^- K^- produced by the interference of the non-resonant decay amplitude with the resonant amplitudes. The resonant states which subsequently decay into pi^+ pi^- and K^+ K^- or K^- pi^+ are charmonium c(bar) c states with J^P = 0^+, 1^-, 1^+ or the phi(1020) meson. We find that the largest partial width asymmetry comes from the chi_c0 resonance, while the resonances K^*_0(1430) and psi(2S) give a partial width asymmetry of the order 10%.
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