Observation of the Λb0→χc1(3872)pK−\Lambda_b^0\rightarrow \chi_{c1}(3872)pK^- decay

International audienceUsing proton-proton collision data, collected with the LHCb detector and corresponding to 1.0, 2.0 and 1.9 fb$^{−1}$ of integrated luminosity at the centre-of-mass energies of 7, 8, and 13 TeV, respectively, the decay {\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1} (3872)pK$^{−}$ with χ$_{c1}$(3872) → J/ψ π$^{+}$π$^{−}$ is observed for the first time. The significance of the observed signal is in excess of seven standard deviations. It is found that (58 ± 15)% of the decays proceed via the two-body intermediate state χ$_{c1}$(3872)Λ(1520). The branching fraction with respect to that of the ${\Lambda}_{\mathrm{b}}^0$ → ψ(2S)pK$^{−}$ decay mode, where the ψ(2S) meson is reconstructed in the J/ψ π$^{+}$π$^{−}$ final state, is measured to be: $ \frac{\beta \left({\Lambda}_{\mathrm{b}}^0\to {\upchi}_{\mathrm{c}1}(3872){\mathrm{pK}}^{-}\right)}{\beta \left({\Lambda}_{\mathrm{b}}^0\to \uppsi \left(2\mathrm{S}\right){\mathrm{pK}}^{-}\right)}\times \frac{\beta \left({\upchi}_{\mathrm{c}1}(3872)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}{\beta \left(\uppsi \left(2\mathrm{S}\right)\to \mathrm{J}/\uppsi {\uppi}^{+}{\uppi}^{-}\right)}=\left(5.4\pm 1.1\pm 0.2\right)\times {10}^{-2},

Updated measurement of time-dependent CP-violating observables in Bs0→J/ψK+K−B^{0}_{s}\to J/\psi K^+ K^- decays

International audienceThe decay-time-dependent $CP$ asymmetry in ${{B} ^0_{s}} \rightarrow J/\psi {{K} ^+} {{K} ^-}$ decays is measured using proton–proton collision data, corresponding to an integrated luminosity of $1.9\,\mathrm{fb}^{-1}$ , collected with the LHCb detector at a centre-of-mass energy of $13\,\mathrm {TeV}$ in 2015 and 2016. Using a sample of approximately 117 000 signal decays with an invariant ${{K} ^+} {{K} ^-}$ mass in the vicinity of the $\phi (1020)$ resonance, the $CP$ -violating phase $\phi _s$ is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the ${{B} ^0_{s}}$ - ${{\overline{B}{}} {}^0_{s}}$ system, $\Delta \Gamma _s$ . The difference of the average ${{B} ^0_{s}}$ and ${{B} ^0}$ meson decay widths, $\Gamma _s-\Gamma _d$ , is determined using in addition a sample of ${{B} ^0} \rightarrow J/\psi {{K} ^+} {{\pi } ^-}$ decays. The values obtained are $\phi _s = -0.083\pm 0.041\pm 0.006\mathrm { \,rad}$ , $\Delta \Gamma _s = 0.077 \pm 0.008 \pm 0.003 {\mathrm { \,ps^{-1}}}$ and $\Gamma _s-\Gamma _d = -0.0041 \pm 0.0024 \pm 0.0015{\mathrm { \,ps^{-1}}}$ , where the first uncertainty is statistical and the second systematic. These are the most precise single measurements of these quantities to date and are consistent with expectations based on the Standard Model and with a previous LHCb analysis of this decay using data recorded at centre-of-mass energies 7 and 8 TeV. Finally, the results are combined with recent results from ${{B} ^0_{s}} \rightarrow J/\psi {{\pi } ^+} {{\pi } ^-}$ decays obtained using the same dataset as this analysis, and with previous independent LHCb results

Measurement of CP observables in the process B0^{0} → DK∗0^{*0} with two- and four-body D decays

International audienceMeasurements of CP observables in B$^{0}$ → DK$^{∗0}$ decays are presented, where D represents a superposition of D$^{0}$ and ${\overline{D}}^0$ 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 $\sqrt{s}=7,8$ and 13 TeV, respectively. First observations of the decays B$^{0}$ → D(π$^{+}$K$^{−}$)K$^{∗0}$ and B$^{0}$ → D(π$^{+}$π$^{−}$π$^{+}$π$^{−}$)K$^{∗0}$ are obtained. The measured observables are interpreted in terms of the CP -violating weak phase γ