Observation of a new Ξb−\Xi_b^- resonance

International audienceFrom samples of pp collision data collected by the LHCb experiment at s=7, 8 and 13 TeV, corresponding to integrated luminosities of 1.0, 2.0 and 1.5  fb-1, respectively, a peak in both the Λb0K- and Ξb0π- invariant mass spectra is observed. In the quark model, radially and orbitally excited Ξb- resonances with quark content bds are expected. Referring to this peak as Ξb(6227)-, the mass and natural width are measured to be mΞb(6227)-=6226.9±2.0±0.3±0.2  MeV/c2 and ΓΞb(6227)-=18.1±5.4±1.8  MeV/c2, where the first uncertainty is statistical, the second is systematic, and the third, on mΞb(6227)-, is due to the knowledge of the Λb0 baryon mass. Relative production rates of the Ξb(6227)-→Λb0K- and Ξb(6227)-→Ξb0π- decays are also reported

Observation of Bs0→D‾∗0ϕB_s^0 \to \overline{D}^{*0} \phi and search for B0→D‾0ϕB^0 \to \overline{D}^0 \phi decays

International audienceThe first observation of the Bs0→D¯*0ϕ decay is reported, with a significance of more than seven standard deviations, from an analysis of pp collision data corresponding to an integrated luminosity of 3  fb-1, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction is measured relative to that of the topologically similar decay B0→D¯0π+π- and is found to be B(Bs0→D¯*0ϕ)=(3.7±0.5±0.3±0.2)×10-5, where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the B0→D¯0π+π- decay. The fraction of longitudinal polarization in this decay is measured to be fL=(73±15±4)%. The most precise determination of the branching fraction for the Bs0→D¯0ϕ decay is also obtained, B(Bs0→D¯0ϕ)=(3.0±0.3±0.2±0.2)×10-5. An upper limit, B(B0→D¯0ϕ)<2.0 (2.3)×10-6 at 90% (95%) confidence level is set. A constraint on the ω-ϕ mixing angle δ is set at |δ|<5.2° (5.5°) at 90% (95%) confidence level

Observation of the decay Bs0→D‾0K+K−B_s^0 \to \overline{D}^0 K^+ K^-

International audienceThe first observation of the Bs0→D¯0K+K- decay is reported, together with the most precise branching fraction measurement of the mode B0→D¯0K+K-. The results are obtained from an analysis of pp collision data corresponding to an integrated luminosity of 3.0  fb-1. The data were collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction of the B0→D¯0K+K- decay is measured relative to that of the decay B0→D¯0π+π- to be B(B0→D¯0K+K-)B(B0→D¯0π+π-)=(6.9±0.4±0.3)%, where the first uncertainty is statistical and the second is systematic. The measured branching fraction of the Bs0→D¯0K+K- decay mode relative to that of the corresponding B0 decay is B(Bs0→D¯0K+K-)B(B0→D¯0K+K-)=(93.0±8.9±6.9)%. Using the known branching fraction of B0→D¯0π+π-, the values of B(B0→D¯0K+K-)=(6.1±0.4±0.3±0.3)×10-5 and B(Bs0→D¯0K+K-)=(5.7±0.5±0.4±0.5)×10-5 are obtained, where the third uncertainties arise from the branching fraction of the decay modes B0→D¯0π+π- and B0→D¯0K+K-, respectively

Observation of Bs0→Dˉ∗0ϕB_s^0 \to \bar{D}^{*0} \phi and search for B0→Dˉ0ϕB^0 \to \bar{D}^0 \phi decays

The first observation of the $B^0_s → \bar{D}^{*0}ϕ$ decay is reported, with a significance of more than seven standard deviations, from an analysis of pp collision data corresponding to an integrated luminosity of 3  fb$^{−1}$, collected with the LHCb detector at center-of-mass energies of 7 and 8 TeV. The branching fraction is measured relative to that of the topologically similar decay $B^0 → \bar{D}^0 π^+ π^−$ and is found to be $\mathcal{B}(B^0_s → \bar{D}^{*0}ϕ)=(3.7±0.5±0.3±0.2) × 10^{−5}$, where the first uncertainty is statistical, the second systematic, and the third from the branching fraction of the $B^0 → \bar{D}^0 π^+ π^−$ decay. The fraction of longitudinal polarization in this decay is measured to be $f_L = (73±15±4)\%$. The most precise determination of the branching fraction for the $B^0_s → \bar{D}^{0}ϕ$ decay is also obtained, $\mathcal{B}(B^0_s → \bar{D}^0 ϕ)=(3.0±0.3±0.2±0.2) × 10^{−5}$. An upper limit,$\mathcal{B}(B^0 → \bar{D}^0 ϕ) < 2.0 (2.3) × 10^{−6}$ at 90% (95%) confidence level is set. A constraint on the $ω−ϕ$ mixing angle $δ$ is set at $|δ| < 5.2°$ (5.5°) at 90% (95%) confidence level

Evidence for an ηc(1S)π−\eta _c(1S) \pi ^- resonance in B0→ηc(1S)K+π−B^0 \rightarrow \eta _c(1S) K^+\pi ^- decays

International audienceA Dalitz plot analysis of ${{B} ^0} \!\rightarrow \eta _c(1S) {{K} ^+} {{\pi } ^-}$ decays is performed using data samples of pp collisions collected with the $\text{ LHCb }$ detector at centre-of-mass energies of ${\sqrt{s}} =7,~8$ and $13{\,\mathrm {Te}\mathrm {V}}$ , corresponding to a total integrated luminosity of $4.7 \,\text{ fb }^{-1}$ . A satisfactory description of the data is obtained when including a contribution representing an exotic $\eta _c(1S) \pi ^-$ resonant state. The significance of this exotic resonance is more than three standard deviations, while its mass and width are $4096 \pm 20~^{+18-22} \,\mathrm {Me}\mathrm {V}$ and $152 \pm 58~^{+60-35} \,\mathrm {Me}\mathrm {V}$ , respectively. The spin-parity assignments $J^P=0^+$ and $J^{P}=1^-$ are both consistent with the data. In addition, the first measurement of the ${{B} ^0} \!\rightarrow \eta _c(1S) {{K} ^+} {{\pi } ^-}$ branching fraction is performed and gives $\begin{aligned} \displaystyle \mathcal {B}({{B} ^0} \!\rightarrow \eta _c(1S) {{K} ^+} {{\pi } ^-} ) = (5.73 \pm 0.24 \pm 0.13 \pm 0.66) \times 10^{-4}, \end{aligned}$ where the first uncertainty is statistical, the second systematic, and the third is due to limited knowledge of external branching fractions

Observation of the decay B‾s0→χc2K+K− {\overline{B}}_s^0\to {\chi}_{c2}{K}^{+}{K}^{-} in the ϕ\phi mass region

The $\overline{B_s^0} \rightarrow \chi_{c2} K^+ K^-$ decay mode is observed and its branching fraction relative to the corresponding $\chi_{c1}$ decay mode, in a $\pm 15 \textrm{MeV}/c^2$ window around the $\phi$ mass, is found to be $\frac{\mathcal{B}(\overline{B_s^0} \rightarrow \chi_{c2} K^+ K^-) }{ \mathcal{B}(\overline{B_s^0} \rightarrow \chi_{c1} K^+ K^-)} = (17.1 \pm 3.1 \pm 0.4 \pm 0.9)\%,$ where the first uncertainty is statistical, the second systematic and the third due to the knowledge of the branching fractions of radiative $\chi_c$ decays. The decay mode $\overline{B_s^0} \rightarrow \chi_{c1} K^+ K^-$ allows the $B_s^0$ mass to be measured as $m(B_s^0) = 5366.83 \pm 0.25 \pm 0.27 \, \textrm{MeV}/c^2,$ where the first uncertainty is statistical and the second systematic. A combination of this result with other LHCb determinations of the $B_s^0$ mass is made

Measurement of Angular and CP Asymmetries in D0→π+π−μ+μ−D^0\to\pi^+\pi^-\mu^+\mu^- and D0→K+K−μ+μ−D^0\to K^+K^-\mu^+\mu^- decays

International audienceThe first measurements of the forward-backward asymmetry of the dimuon pair (AFB), the triple-product asymmetry (A2ϕ), and the charge-parity-conjugation asymmetry (ACP), in D0→π+π-μ+μ- and D0→K+K-μ+μ- decays are reported. They are performed using data from proton-proton collisions collected with the LHCb experiment from 2011 to 2016, corresponding to a total integrated luminosity of 5  fb-1. The asymmetries are measured to be AFB(D0→π+π-μ+μ-)=(3.3±3.7±0.6)%, A2ϕ(D0→π+π-μ+μ-)=(-0.6±3.7±0.6)%, ACP(D0→π+π-μ+μ-)=(4.9±3.8±0.7)%, AFB(D0→K+K-μ+μ-)=(0±11±2)%, A2ϕ(D0→K+K-μ+μ-)=(9±11±1)%, ACP(D0→K+K-μ+μ-)=(0±11±2)%, where the first uncertainty is statistical and the second systematic. The asymmetries are also measured as a function of the dimuon invariant mass. The results are consistent with the standard model predictions