Study of B-→D K-π+π- and B-→D π-π+π- decays and determination of the CKM angle γ

Abstract

We report a study of the suppressed B− → DK−π +π − and favored B− → Dπ−π +π − decays, where the neutral D meson is detected through its decays to the K∓π ± 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− → DK−π +π − and favored B− → Dπ−π +π − modes, as well as in the doubly Cabibbo-suppressed D → K+π − final state of the B− → Dπ−π +π − decay. Evidence for the ADS suppressed decay B− → DK−π +π −, with D → K+π −, is also presented. From the observed yields in the B− → DK−π +π −, B− → Dπ−π +π − and their charge conjugate decay modes, the most probably value of the weak phase γ corresponds to γ = (74+20 −19) o . This is one of the most precise single-measurement determinations of γ to date.