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Register a new userObservation of the annihilation decay mode $B^{0}to K^{+}K^{-}$
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Stefano Perazzini Stefano Perazzini
Publication date
2016
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English
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A search for the $B^{0}to K^{+}K^{-}$ decay is performed using $pp$-collision data collected by LHCb. The data set corresponds to integrated luminosities of 1 and 2 fb$^{-1}$ at center-of-mass energies of 7 and 8 TeV, respectively. This decay is observed for the first time, with a significance of more than five standard deviations. The analysis also results in an improved measurement of the branching fraction for the $B_s^0to pi^+pi^-$ decay. The measured branching fractions are $BR(B^0to K^+K^-) = (7.80 pm 1.27 pm 0.81 pm 0.21) times 10^{-8}$ and $BR(B_s^0topi^+pi^-) = (6.91 pm 0.54 pm 0.63 pm 0.19 pm 0.40) times 10^{-7}$. The first uncertainty is statistical, the second is systematic, the third is due to the uncertainty on the $B^0to K^+pi^-$ branching fraction used as a normalization. For the $B_s^0$ mode, the fourth accounts for the uncertainty on the ratio of the probabilities for $b$ quarks to hadronize into $B_s^0$ and $B^0$ mesons.
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We report a search for charmless hadronic decays of neutral $B$ mesons to $eta K^{*}(892)^{0}$. The results are based on a 711fb$^{-1}$ data sample that contains $772times 10^6 Boverline{B}$ pairs, collected at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric energy $e^+e^-$ collider. We observe the decay for the first time with a significance of 5.0 standard deviations and obtain its branching fraction ${cal B}[B^0toeta K^{*}(892)^{0}]=[2.6pm0.7{rm (stat)}pm0.2{rm (syst)}]times 10^{-6}$. We also measure the $CP$ violating asymmetry as ${cal A}_{CP}[B^0toeta K^{*}(892)^{0}]=-0.22pm0.29{rm (stat)}pm0.07{rm syst}$.
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The first observation of the $B_s^0 to overline{D}^0 K^+ K^-$ decay is reported, together with the most precise branching fraction measurement of the mode $B^0 to overline{D}^0 K^+ K^-$. The results are obtained from an analysis of $pp$ collision data corresponding to an integrated luminosity of $3.0~textrm{fb}^{-1}$. The data were collected with the LHCb detector at centre-of-mass energies of $7$ and $8$ TeV. The branching fraction of the $B^0 to overline{D}^0 K^+ K^-$ decay is measured relative to that of the decay $B^0 to overline{D}^0 pi^+ pi^-$ to be $$frac{mathcal{B}(B^0 to overline{D}^0 K^+ K^-)}{mathcal{B}(B^0 to overline{D}^0 pi^+ pi^-)} = (6.9 pm 0.4 pm 0.3)%,$$ where the first uncertainty is statistical and the second is systematic. The measured branching fraction of the $B_s^0 to overline{D}^0 K^+ K^-$ decay mode relative to that of the corresponding $B^0$ decay is $$frac{mathcal{B}(B_s^0 to overline{D}^0 K^+ K^-)}{mathcal{B}(B^0 to overline{D}^0 K^+ K^-)} = (93.0 pm 8.9 pm 6.9)%.$$ Using the known branching fraction of ${B^0 to overline{D}^0 pi^+ pi^-}$, the values of ${{mathcal B}(B^0 to overline{D}^0 K^+ K^- )=(6.1 pm 0.4 pm 0.3 pm 0.3) times 10^{-5}}$, and ${{cal B}(B_s^0 to overline{D}^0 K^+ K^-)=}$ $(5.7 pm 0.5 pm 0.4 pm 0.5) times 10^{-5}$ are obtained, where the third uncertainties arise from the branching fraction of the decay modes ${B^0 to overline{D}^0 pi^+ pi^-}$ and $B^0 to overline{D}^0 K^+ K^-$, respectively.
The B -> D^{(*)} K^- K^{(*)0} decays have been observed for the first time. The branching fractions of the B -> D^{(*)} K^- K^{(*)0} decay modes are measured. Significant signals are found for the B -> D^{(*)} K^- K^{*0} and B^- -> D^0 K^- K^0_S decay modes. The invariant mass and polarization distributions for the K^-K^{*0} and K^-K^0_S subsystems have been studied. For the K^-K^{*0} sybsystem these distributions agree well with those expected for two-body B -> D^{(*)} a_1^-(1260) decays, with a_1^-(1260) -> K^- K^{*0}. The analysis was done using 29.4 fb^{-1} of data collected with the Belle detector at the e^+ e^- asymmetric collider KEKB.
We measure the decay $B_s^0rightarrow K^0overline{K}^0$ using data collected at the $Upsilon(5S)$ resonance with the Belle detector at the KEKB $e^+e^-$ collider. The data sample used corresponds to an integrated luminosity of 121.4 ${rm fb^{-1}}$. We measure a branching fraction $mathcal{B}(B_s^0rightarrow K^0overline{K}^0) = [19.6,^{+5.8}_{-5.1}({rm stat.}),pm1.0({rm sys.}),pm 2.0(N^{}_{B_s^0overline{B}_s^0})]times 10^{-6}$ with a significance of 5.1 standard deviations. This measurement constitutes the first observation of this decay.
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