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Register a new userObservation of the decay $B_s^0rightarrow K^0overline{K}^0$
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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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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 first observation of the decay $B_s^0 rightarrow phi bar{K}^{*0}$ is reported. The analysis is based on a data sample corresponding to an integrated luminosity of 1.0 fb$^{-1}$ of $pp$ collisions at $sqrt{s} = 7 TeV$, collected with the LHCb detector. A yield of $30 pm 6$ $B_s^0 rightarrow (K^+K^-)(K^-pi^+)$ decays is found in the mass windows $1012.5 < M(K^+K^-) < 1026.5 MeV/c^2$ and $746 < M(K^-pi^+)< 1046 MeV/c^2$. The signal yield is found to be dominated by $B_s^0 rightarrow phi bar{K}^{*0}$ decays, and the corresponding branching fraction is measured to be ${cal B}(B_s^0 rightarrow phi bar{K}^{*0}) = (1.10 pm 0.24 (stat) pm 0.14 (syst) pm 0.08 (f_d/f_s)) times 10^{-6}$, where the uncertainties are statistical, systematic and from the ratio of fragmentation fractions $f_d/f_s$ which accounts for the different production rate of $B^0$ and $B_s^0$ mesons. The significance of $B_s^0 rightarrow phi bar{K}^{*0}$ signal is 6.1 standard deviations. The fraction of longitudinal polarization in $B_s^0 rightarrow phi bar{K}^{*0}$ decays is found to be $f_0 = 0.51 pm 0.15 (stat) pm 0.07 (syst)$.
Using a data sample of $2.93~fb^{-1}$ of $e^+e^-$ collisions collected at $sqrt{s}=3.773 GeV$ in the BESIII experiment, we perform an analysis of the decay $D^0rightarrow K_{S}^{0} K^{+} K^{-}$. The Dalitz plot is analyzed using $1856pm 45$ flavor-tagged signal decays. We find that the Dalitz plot is well described by a set of six resonances: $a_0(980)^0$, $a_0(980)^+$, $phi(1020)$, $a_2(1320)^+$, $a_2(1320)^-$ and $a_0(1450)^-$. Their magnitudes, phases and fit fractions are determined as well as the coupling of $a_0(980)$ to $Kbar{K}$, $g_{Kbar{K}}=3.77pm 0.24text{(stat.)}pm0.35text{(sys.)} GeV$. The branching fraction of the decay $D^0rightarrow K_{S}^{0} K^{+} K^{-}$ is measured using $11660pm 118$ untagged signal decays to be $(4.51pm 0.05text{(stat.)}pm 0.16text{(sys.)})10^{-3}$. Both measurements are limited by their systematic uncertainties.
The $overline{B_s^0} rightarrow chi_{c2} K^+ K^- $ decay mode is observed and its branching fraction relative to the corresponding $chi_{c1}$ decay mode, in a $pm 15 textrm{MeV}/c^2$ window around the $phi$ mass, is found to be $frac{mathcal{B}(overline{B_s^0} rightarrow chi_{c2} K^+ K^-) }{ mathcal{B}(overline{B_s^0} rightarrow chi_{c1} K^+ K^-)} = (17.1 pm 3.1 pm 0.4 pm 0.9)%,$ where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative $chi_c$ decays. The decay mode $overline{B_s^0} rightarrow chi_{c1} K^+ K^- $ allows the $ B_s^0$ mass to be measured as $m(B_s^0) = 5366.83 pm 0.25 pm 0.27 , textrm{MeV}/c^2,$ where the first uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the $B_s^0$ mass is made.
The first observation of the decay $kstarkstar$ is reported using 35invpb of data collected by LHCb in proton-proton collisions at a centre-of-mass energy of 7 TeV. A total of $49.8 pm 7.5$ $B^0_s rightarrow (K^+pi^-)(K^-pi^+)$ events are {observed within $pm 50 mevcc$ of the Bs mass and $746 mevcc < m_{Kpi}< 1046 mevcc$, mostly coming from a resonant $kstarkstar$ signal.} The branching fraction and the CP-averaged Kstarz longitudinal polarization fraction are measured to be {$BR(kstarkstar) = (2.81 pm 0.46 ({rm stat.}) pm 0.45 ({rm syst.}) pm 0.34, (f_s/f_d))times10^{-5}$} and $f_L = 0.31 pm 0.12 ({rm stat.}) pm 0.04 ({rm syst.})$.
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