Study of B−→DK−π+π− and B−→Dπ−π+π− decays and determination of the CKM angle γ

Le résumé fourni par la source

We report a study of the suppressed ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and favored ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decays, where the neutral $D$ meson is detected through its decays to the ${K}^{\ensuremath{\mp}}{\ensuremath{\pi}}^{\ifmmode\pm\else\textpm\fi{}}$ and $CP$ -even ${K}^{+}{K}^{\ensuremath{-}}$ and ${\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ final states. The measurement is carried out using a proton-proton collision data sample collected by the LHCb experiment, corresponding to an integrated luminosity of $3.0\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. We observe the first significant signals in the $CP$ -even final states of the $D$ meson for both the suppressed ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and favored ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ modes, as well as in the doubly Cabibbo suppressed $D\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ final state of the ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decay. Evidence for the suppressed decay ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, with $D\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, is also presented. From the observed yields in the ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{K}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$, ${B}^{\ensuremath{-}}\ensuremath{\rightarrow}D{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and their charge conjugate decay modes, the most probable value of the weak phase $\ensuremath{\gamma}$ corresponds to $\ensuremath{\gamma}=(7{4}_{\ensuremath{-}19}^{+20})\ifmmode^\circ\else\textdegree\fi{}$. This is one of the most precise single-measurement determinations of $\ensuremath{\gamma}$ to date.

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