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Register a new userModel-independent determination of the strong-phase difference between D^0 and D^0-bar-> K^0_S,L h^+ h^- (h=pi,K) and its impact on the measurement of the CKM angle gamma/phi_3
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We report the first determination of the relative strong-phase difference between D^0 -> K^0_S,L K^+ K^- and D^0-bar -> K^0_S,L K^+ K^-. In addition, we present updated measurements of the relative strong-phase difference between D^0 -> K^0_S,L pi^+ pi^- and D^0-bar -> K^0_S,L pi^+ pi^-. Both measurements exploit the quantum coherence between a pair of D^0 and D^0-bar mesons produced from psi(3770) decays. The strong-phase differences measured are important for determining the Cabibbo-Kobayashi-Maskawa angle gamma/phi_3 in B^- -> K^- D^0-tilde decays, where D^0-tilde is a D^0 or D^0-bar meson decaying to K^0_S h^+ h^- (h=pi,K), in a manner independent of the model assumed to describe the D^0 -> K^0_S h^+ h^- decay. Using our results, the uncertainty in gamma/phi_3 due to the error on the strong-phase difference is expected to be between 1.7 and 3.9 degrees for an analysis using B^- K^- D^0-tilde D^0-tilde -> K^0_S pi^+ pi^- decays, and between 3.2 and 3.9 degrees for an analysis based on B^- -> K^- D^0-tilde, D^0-tilde -> K^0_S K^+ K^- decays. A measurement is also presented of the CP-odd fraction, F_-, of the decay D^0 -> K^0_S K^+ K^- in the region of the phi -> K^+ K^- resonance. We find that in a region within 0.01 GeV^2/c^4 of the nominal phi mass squared F_- > 0.91 at the 90% confidence level.
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Crucial inputs for a variety of $CP$-violation studies can be determined through the analysis of pairs of quantum-entangled neutral $D$ mesons, which are produced in the decay of the $psi(3770)$ resonance. The relative strong-phase parameters between $D^0$ and $bar{D}^0$ in the decays $D^0rightarrow K^0_{S,L}pi^+pi^-$ are studied using 2.93~${rm fb}^{-1}$ of $e^+e^-$ annihilation data delivered by the BEPCII collider and collected by the BESIII detector at a center-of-mass energy of 3.773 GeV. Results are presented in regions of the phase space of the decay. These are the most precise measurements to date of the strong-phase parameters in $D to K_{S,L}^0pi^+pi^-$ decays. Using these parameters, the associated uncertainty on the Cabibbo-Kobayashi-Maskawa angle $gamma/phi_3$ is expected to be between $0.7^circ$ and $1.2^circ$, for an analysis using the decay $B^{pm}rightarrow DK^{pm}$, $Drightarrow K^0_Spi^+pi^-$, where $D$ represents a superposition of $D^0$ and $bar{D^0}$ states. This is a factor of three smaller than that achievable with previous measurements. Furthermore, these results provide valuable input for charm-mixing studies, other measurements of $CP$ violation, and the measurement of strong-phase parameters for other $D$-decay modes.
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.
A model-dependent amplitude analysis of the decay $B^0rightarrow D(K^0_Spi^+pi^-) K^{*0}$ is performed using proton-proton collision data corresponding to an integrated luminosity of 3.0fb$^{-1}$, recorded at $sqrt{s}=7$ and $8 TeV$ by the LHCb experiment. The CP violation observables $x_{pm}$ and $y_{pm}$, sensitive to the CKM angle $gamma$, are measured to be begin{eqnarray*} x_- &=& -0.15 pm 0.14 pm 0.03 pm 0.01, y_- &=& 0.25 pm 0.15 pm 0.06 pm 0.01, x_+ &=& 0.05 pm 0.24 pm 0.04 pm 0.01, y_+ &=& -0.65^{+0.24}_{-0.23} pm 0.08 pm 0.01, end{eqnarray*} where the first uncertainties are statistical, the second systematic and the third arise from the uncertainty on the $Drightarrow K^0_S pi^+pi^-$ amplitude model. These are the most precise measurements of these observables. They correspond to $gamma=(80^{+21}_{-22})^{circ}$ and $r_{B^0}=0.39pm0.13$, where $r_{B^0}$ is the magnitude of the ratio of the suppressed and favoured $B^0rightarrow D K^+ pi^-$ decay amplitudes, in a $Kpi$ mass region of $pm50 MeV$ around the $K^*(892)^0$ mass and for an absolute value of the cosine of the $K^{*0}$ decay angle larger than $0.4$.
A measurement of $CP$-violating observables is performed using the decays $B^pmto D K^pm$ and $B^pmto D pi^pm$, where the $D$ meson is reconstructed in one of the self-conjugate three-body final states $K_{mathrm S}pi^+pi^-$ and $K_{mathrm S}K^+K^-$ (commonly denoted $K_{mathrm S} h^+h^-$). The decays are analysed in bins of the $D$-decay phase space, leading to a measurement that is independent of the modelling of the $D$-decay amplitude. The observables are interpreted in terms of the CKM angle $gamma$. Using a data sample corresponding to an integrated luminosity of $9,text{fb}^{-1}$ collected in proton-proton collisions at centre-of-mass energies of $7$, $8$, and $13,text{TeV}$ with the LHCb experiment, $gamma$ is measured to be $left(68.7^{+5.2}_{-5.1}right)^circ$. The hadronic parameters $r_B^{DK}$, $r_B^{Dpi}$, $delta_B^{DK}$, and $delta_B^{Dpi}$, which are the ratios and strong-phase differences of the suppressed and favoured $B^pm$ decays, are also reported.
A binned Dalitz plot analysis of the decays $B^0 to D K^{ast 0}$, with $D to K_{S}^{0} pi^{+} pi^{-}$ and $K_{S}^{0} K^{+} K^{-}$, is performed to measure the observables $x_pm$ and $y_pm$, which are related to the CKM angle $gamma$ and the hadronic parameters of the decays. The $D$ decay strong phase variation over the Dalitz plot is taken from measurements performed at the CLEO-c experiment, making the analysis independent of the $D$ decay model. With a sample of proton-proton collision data, corresponding to an integrated luminosity of $3.0,rm{fb}^{-1}$, collected by the LHCb experiment, the values of the $CP$ violation parameters are found to be $x_+ = 0.05 pm 0.35 pm 0.02$, $x_-=-0.31pm 0.20 pm 0.04$, $y_+=-0.81pm 0.28pm 0.06$ and $y_-=0.31pm 0.21 pm 0.05$, where the first uncertainties are statistical and the second systematic. These observables correspond to values $gamma$ = $(71 pm 20)^circ$, $r_{B^0} = 0.56pm 0.17$ and $delta_{B^0} = (204,^{+21}_{-20})^circ$. The parameters $r_{B^0}$ and $delta_{B^0}$ are the magnitude ratio and strong phase difference between the suppressed and favoured $B^0$ decay amplitudes, and have been measured in a region of $pm 50$ MeV/$c^2$ around the $K^{ast}(892)^{0}$ mass and with the magnitude of the cosine of the $K^{ast}(892)^{0}$ helicity angle larger than 0.4.
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