Study of $B^{-}\to DK^-π^+π^-$ and $B^-\to Dπ^-π^+π^-$ decays and determination of the CKM angle $γ$

Abstract

We report a study of the suppressed $B^-\to DK^-π^+π^-$ and favored $B^-\to Dπ^-π^+π^-$ decays, where the neutral $D$ meson is detected through its decays to the $K^{\mp}π^{\pm}$ and CP-even $K^+K^-$ and $π^+π^-$ 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~fb$^{-1}$. We observe the first significant signals in the CP-even final states of the $D$ meson for both the suppressed $B^-\to DK^-π^+π^-$ and favored $B^-\to Dπ^-π^+π^-$ modes, as well as in the doubly Cabibbo-suppressed $D\to K^+π^-$ final state of the $B^-\to Dπ^-π^+π^-$ decay. Evidence for the ADS suppressed decay $B^{-}\to DK^-π^+π^-$, with $D\to K^+π^-$, is also presented. From the observed yields in the $B^-\to DK^-π^+π^-$, $B^-\to Dπ^-π^+π^-$ and their charge conjugate decay modes, we measure the value of the weak phase to be $γ=(74^{+20}_{-19})^{\rm o}$. This is one of the most precise single-measurement determinations of $γ$ to date.

22 pages, 9 figures; All figures and tables, along with any supplementary material and additional information, are available at https://lhcbproject.web.cern.ch/lhcbproject/Publications/LHCbProjectPublic/LHCb-PAPER-2015-020.html