Measurement of the CKM angle gamma using B^pm --> D K^pm with D-->K_Spi^+pi^-, K_SK^+K^- decays

A binned Dalitz plot analysis of $B^pm to D K^pm$ decays, with $D to K_S pi^+pi^-$ and $D to K_S K^+ K^-$, is performed to measure the CP-violating observables $x_{pm}$ and $y_{pm}$, which are sensitive to the Cabibbo-Kobayashi-Maskawa angle $gamma$. The analysis exploits a sample of proton-proton collision data corresponding to 3.0invfb collected by the LHCb experiment. Measurements from CLEO-c of the variation of the strong-interaction phase of the $D$ decay over the Dalitz plot are used as inputs. The values of the parameters are found to be $x_+ = (-7.7 pm 2.4 pm 1.0 pm 0.4)times 10^{-2}$, $x_- = (2.5 pm 2.5 pm 1.0 pm 0.5) times 10^{-2}$, $y_+ = (-2.2 pm 2.5 pm 0.4 pm 1.0)times 10^{-2}$, and $y_- = (7.5 pm 2.9 pm 0.5 pm 1.4) times 10^{-2}$. The first, second, and third uncertainties are the statistical, the experimental systematic, and that associated with the precision of the strong-phase parameters. These are the most precise measurements of these observables and correspond to $gamma = (62^{,+15}_{,-14})^circ$, with a second solution at $gamma to gamma + 180^circ$, and $r_B = 0.080^{+ 0.019}_{-0.021}$, where $r_B$ is the ratio between the suppressed and favoured $B$ decay amplitudes.

Studies of the decays D^0 rightarrow K_S^0K^-pi^+ and D^0 rightarrow K_S^0K^+pi^-

The first measurements of the coherence factor R_{K_S^0Kpi} and the average strong--phase difference delta^{K_S^0Kpi} in D^0 to K_S^0 K^mppi^pm decays are reported. These parameters can be used to improve the determination of the unitary triangle angle gamma in B^- rightarrow $widetilde{D}K^-$ decays, where $widetilde{D}$ is either a D^0 or a D^0-bar meson decaying to the same final state, and also in studies of charm mixing. The measurements of the coherence factor and strong-phase difference are made using quantum-correlated, fully-reconstructed D^0D^0-bar pairs produced in e^+e^- collisions at the psi(3770) resonance. The measured values are R_{K_S^0Kpi} = 0.70 pm 0.08 and delta^{K_S^0Kpi} = (0.1 pm 15.7)$^circ$ for an unrestricted kinematic region and R_{K*K} = 0.94 pm 0.12 and delta^{K*K} = (-16.6 pm 18.4)$^circ$ for a region where the combined K_S^0 pi^pm invariant mass is within 100 MeV/c^2 of the K^{*}(892)^pm mass. These results indicate a significant level of coherence in the decay. In addition, isobar models are presented for the two decays, which show the dominance of the K^*(892)^pm resonance. The branching ratio {B}(D^0 rightarrow K_S^0K^+pi^-)/{B}(D^0 rightarrow K_S^0K^-pi^+) is determined to be 0.592 pm 0.044 (stat.) pm 0.018 (syst.), which is more precise than previous measurements.