Study of B− → DK−π+π− and B− → Dπ−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 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 probable value of the weak phase γ corresponds to γ=(74+20−19)°. This is one of the most precise single-measurement determinations of γ to date.