An analysis of B± → DK± and B± → Dπ± decays is presented where the D meson is reconstructed in the four-body nal state K±π∓π+π-. Using LHCb data corresponding to an integrated luminosity of 1.0 fb-1, rst observations are made of the suppressed ADS modes B± →[π±K∓π+π-] D K± and B± → [π±K∓π+π-]Dπ± with a signicance of 5.1σ and greater than 10σ, respectively. Measurements of CP asymmetries and CP-conserving ratios of partial widths from this family of decays are also performed. The magnitude of the ratio between the suppressed and favoured B± → DK± amplitudes is determined to be rKB = 0.097±0.011. © CERN for the benet of the LHCb Collaboration.
- Nuclear and High Energy Physics