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Free keywords:
High Energy Physics - Experiment, hep-ex
MPINP:
LHCb - Abteilung Hofmann
Abstract:
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 3.0\invfb 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.
