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Register a new userDetermination of the bar K^0 d scattering length from the reaction pp to d bar K^0 K^+
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The real and imaginary parts of the bar K^0 d scattering length are extracted from the bar K^0 d mass spectrum obtained from the reaction pp to d bar K^0 K^+ measured recently at the Cooler Synchrotron COSY at Julich. We extract a new limit on the K^- d scattering length, namely Im a le 1.3 fm and |Re a| le 1.3 fm. The limit for the imaginary part of the K^- d scattering length is supported by data on the total K^- d cross sections.
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The results of a recent experiment measuring the reaction pp -> dK^+ bar K^0 near threshold are interpreted in terms of a spectator model that encapsulates the main features of the observed K^+ bar K^0 invariant mass distribution. A chi^2 fit to this data leads to an imaginary part of the isovector scattering length in the K bar K channel of Im(a_1) = -(0.63 pm 0.24) fm. We then use the Flatte representation of the scattering amplitude to infer a value Re(a_1) = -(0.02 pm 0.02) fm for the real part under the assumption that scaling is approximately satisfied. We show further that it is not possible to exclude the effects of pi^+eta to K^+ bar K^0 channel coupling within the context of our model.
Using an effective Lagrangian approach as well as the Quark-Gluon Strings Model we analyze near-threshold production of a0(980)-mesons in the reaction NN -> d K bar{K} as well as the background of non-resonant Kbar{K}-pair production. We argue that the reaction pp -> d K^+ bar{K}^0 at an energy release Q<=100 MeV is dominated by the intermediate production of the a0(980)-resonance. At larger energies the non-resonant K^+bar{K}^0-pair production - where the kaons are produced in a relative P-wave - becomes important. Then effects of final-state interactions are evaluated in a unitarized scattering-length approach and found to be in the order of a 20% suppression close to threshold. Thus in present experiments at the Cooler Synchrotron COSY-Julich for Q<=107 MeV the a_0^+ signal can reliably be separated from the non-resonant K^+bar{K^0} background.
We present a measurement of the strong-phase difference between $D^{0}$ and $bar{D}^{0}to K^{0}_{rm S,L}K^{+}K^{-}$ decays, performed through a study of quantum-entangled pairs of charm mesons. The measurement exploits a data sample equivalent to an integrated luminosity of 2.93~fb$^{-1}$, collected by the BESIII detector in $e^{+}e^{-}$ collisions corresponding to the mass of the $psi(3770)$ resonance. The strong-phase difference is an essential input to the determination of the Cabibbo-Kobayashi-Maskawa (CKM) angle $gamma/phi_3$ through the decay $B^{-}to DK^{-}$, where $D$ can be either a $D^{0}$ or a $bar{D}^{0}$ decaying to $K^{0}_{rm S,L}K^{+}K^{-}$. This is the most precise measurement to date of the strong-phase difference in these decays.
We present a study of $Bto X(3872)K$ with X(3872) decaying to $D^{*0}bar D^0$ using a sample of 657 million $Bbar B$ pairs recorded at the $Upsilon(4S)$ resonance with the Belle detector at the KEKB asymmetric-energy $e^+e^-$ collider. Both $D^{*0}to D^0gamma$ and $D^{*0}to D^0pi^0$ decay modes are used. We find a peak of $50.1^{+14.8}_{-11.1}$ events with a mass of $(3872.9^{+0.6 +0.4}_{-0.4 -0.5}){rm MeV}/c^2$, a width of $(3.9^{+2.8 +0.2}_{-1.4 -1.1}){rm MeV}/c^2$ and a product branching fraction ${cal B}(Bto X(3872)K)times{cal B}(X(3872)to D^{*0}bar D^0)=(0.80pm0.20pm0.10)times10^{-4}$, where the first errors are statistical and the second ones are systematic. The significance of the signal is $6.4sigma$. The difference between the fitted mass and the $D^{*0}bar D^0$ threshold is calculated to be $(1.1^{+0.6 +0.1}_{-0.4 -0.3}){rm MeV}/c^2$. We also obtain an upper limit on the product of branching fractions ${cal B}(Bto Y(3940)K)times{cal B}(Y(3940)to D^{*0}bar D^0)$ of $0.67times10^{-4}$ at 90% CL.
Simulation studies are performed to assess the sensitivity of a model-independent analysis of the flavour-tagged decays $D^0 to K^0_{rm S}pi^+pi^-$ and $D^0 to K^0_{rm S}K^+K^-$ to mixing and CP violation. The analysis takes as input measurements of the $D$ decay strong-phase parameters that are accessible in quantum-correlated $D-bar{D}$ pairs produced at the $psi(3770)$ resonance. It is shown that the model-independent approach is well suited to the very large data sets expected at an upgraded LHCb experiment, or future high luminosity $e^+e^-$ facility, and that with 100M $K^0_{rm S}pi^+pi^-$ decays a statistical precision of around 0.01 and $0.7^circ$ is achievable on the CP violation parameters $r_{CP}$ and $a_{CP}$, respectively. Even with this very large sample the systematic uncertainties associated with the strong-phase parameters will not be limiting, assuming that full use is made of the available $psi(3770)$ data sets of CLEO-c and BES-III. Furthermore, it is demonstrated that large flavour-tagged samples can themselves be exploited to provide information on the strong-phase parameters, a feature that will be beneficial in the measurement of the CKM angle $gamma/phi_3$ with $B^- to DK^-$ decays.
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