A precise measurement of the $B^0$ meson oscillation frequency
The oscillation frequency,
Measurements of CP observables in B0 → DK∗0 decays are presented, where D represents a superposition of D0 and 𝐷⎯⎯⎯⎯⎯0D¯0 states. The D meson is reconstructed in the two-body final states K+π−, π+K−, K+K− and π+π−, and, for the first time, in the fourbody final states K+π−π+π−, π+K−π+π− and π+π−π+π−. The analysis uses a sample of neutral B mesons produced in proton-proton collisions, corresponding to an integrated luminosity of 1.0, 2.0 and 1.8 fb−1 collected with the LHCb detector at centre-of-mass energies of 𝑠√=7,8s=7,8 and 13 TeV, respectively. First observations of the decays B0 → D(π+K−)K∗0 and B0 → D(π+π−π+π−)K∗0 are obtained. The measured observables are interpreted in terms of the CP -violating weak phase γ.
The B0sπ± invariant mass distribution is investigated in order to search for possible exotic meson states. The analysis is based on a data sample recorded with the LHCb detector corresponding to 3 fb−1 of pp collision data at s√=7 and 8 TeV. No significant excess is found, and upper limits are set on the production rate of the claimed X(5568) state within the LHCb acceptance. Upper limits are also set as a function of the mass and width of a possible exotic meson decaying to the B0sπ± final state. The same limits also apply to a possible exotic meson decaying through the chain B∗0sπ±, B∗0s→B0sγ where the photon is excluded from the reconstructed decays.
Charm meson oscillations are observed in a time-dependent analysis of the ratio of D0 → K+π −π +π − to D0 → K−π +π −π + decay rates, using data corresponding to an integrated luminosity of 3.0 fb−1 recorded by the LHCb experiment. The measurements presented are sensitive to the phase-space averaged ratio of doubly Cabibbo-suppressed to Cabibbo-favoured amplitudes r K3π D and the product of the coherence factor RK3π D and a charm mixing parameter y 0 K3π . The constraints measured are r K3π D = (5.67±0.12)×10−2 , which is the most precise determination to date, and RK3π D · y 0 K3π = (0.3 ± 1.8) × 10−3 , which provides useful input for determinations of the CP-violating phase γ in B±→ DK±, D→ K∓π ±π ∓π ± decays. The analysis also gives the most precise measurement of the D0 → K+π −π +π − branching fraction, and the first observation of D0–D0 oscillations in this decay mode, with a significance of 8.2 standard deviations.