Abstract
Measurements of CP observables in B± → D(*)K± and B± → D(*)π± decays are presented, where D(∗) indicates a neutral D or D∗ meson that is an admixture of meson and anti-meson states. Decays of the D(∗) meson to the Dπ0 and Dγ final states are partially reconstructed without inclusion of the neutral pion or photon. Decays of the D meson are reconstructed in the K±π∓, K+K−, and π+π− final states. The analysis uses a sample of charged B mesons produced in proton-proton collisions and collected with the LHCb experiment, corresponding to integrated luminosities of 2.0, 1.0, and 5.7 fb−1 taken at centre-of-mass energies of 7, 8, and 13 TeV, respectively. The measurements of partially reconstructed B± → D(*)K± and B± → D(∗)π± with D → K∓π± decays are the first of their kind, and a first observation of the B± → {left(D{pi}^0right)}_{D^{ast }}{pi}^{pm } decay is made with a significance of 6.1 standard deviations. All CP observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle γ.
Highlights
LHCb detector and simulationThe LHCb detector [15, 17] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks
Background from favoured decays misidentified asADS decays is reduced by application of the D mass window and D decay product particle identification (PID) requirements detailed above
All CP observables are measured with world-best precision, and in combination with other LHCb results will provide strong constraints on the CKM angle γ
Summary
The LHCb detector [15, 17] is a single-arm forward spectrometer covering the pseudorapidity range 2 < η < 5, designed for the study of particles containing b or c quarks. The events considered in the analysis are triggered at the hardware level either when one of the final-state tracks of the signal decay deposits enough energy in the calorimeter system, or when one of the other particles in the event, not reconstructed as part of the signal candidate, fulfils any trigger requirement. The RKK/ππ,γ/π0 observable is an average over the D∗ → Dπ0 and D∗ → Dγ modes. Decays of unstable particles are described by EvtGen [22], in which final-state radiation is generated using Photos [23]. Some subdominant sources of background are generated with a fast simulation [27] that mimics the geometric acceptance and tracking efficiency of the LHCb detector as well as the dynamics of the decay via EvtGen
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