46 Search Results

The decay-time-dependent $CP$ asymmetry in $B_s^0\to J/\psi (\to {\mu }^{+}{\mu }^{-})K^{+}{K}^{-}$ decays is measured using proton-proton collision data, corresponding to an integrated luminosity of $6{\mathrm{fb}}^{-1}$ , collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 $B_s^0$ signal decays with an invariant $K^{+}{K}^{more »}$ − mass in the vicinity of the $\varphi \left(1020\right)$ resonance, the $CP$ -violating phase ${\varphi }_s$ is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the $B_s^0\text{−}{\overline{B}}_s^0$ system, $\mathrm{\Delta }{\mathrm{\Gamma }}_s$ , and the difference of the average $B_s^0$ and $B^0$ meson decay widths, ${\mathrm{\Gamma }}_s-{\mathrm{\Gamma }}_d$ . The values obtained are ${\varphi }_s=-0.039\pm 0.022\pm 0.006\mathrm{rad}$ , $\mathrm{\Delta }{\mathrm{\Gamma }}_s=0.0845\pm 0.0044\pm 0.0024{\mathrm{ps}}^{-1}$ , and ${\mathrm{\Gamma }}_s-{\mathrm{\Gamma }}_d=-0.0056_{-0.0015}^{+0.0013}\pm 0.0014{\mathrm{ps}}^{-1}$ , where the first uncertainty is statistical and the second systematic. These are the most precise single measurements to date and are consistent with expectations based on the Standard Model and with the previous LHCb analyses of this decay. These results are combined with previous independent LHCb measurements. The phase ${\varphi }_s$ is also measured independently for each polarization state of the $K^{+}{K}^{-}$ system and shows no evidence for polarization dependence. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

A measurement of time-dependent $CP$ violation in the decays of $B^0$ and ${\overline{B}}^0$ mesons to the final states $J/\psi (\to {\mu }^{+}{\mu }^{-})K_S^0$ , $\psi \left(2S\right)(\to {\mu }^{+}{\mu }^{more »}$ − ) K S 0 and $J/\psi (\to e^{+}{e}^{-})K_S^0$ with $K_S^0\to {\pi }^{+}{\pi }^{-}$ is presented. The data correspond to an integrated luminosity of $6{\mathrm{fb}}^{-1}$ collected at a center-of-mass energy of $\sqrt{s}=13\mathrm{TeV}$ with the LHCb detector. The $CP$ -violation parameters are measured to be $S_{\psi K_S^0}=0.717\pm 0.013\left(\mathrm{stat}\right)\pm 0.008\left(\mathrm{syst}\right)$ and $C_{\psi K_S^0}=0.008\pm 0.012\left(\mathrm{stat}\right)\pm 0.003\left(\mathrm{syst}\right)$ . This measurement of $S_{\psi K_S^0}$ represents the most precise single measurement of the CKM angle $\beta$ to date and is more precise than the current world average. In addition, measurements of the $CP$ -violation parameters of the individual channels are reported and a combination with the LHCb Run 1 measurements is performed. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

Two new excited states, Ω_c(3185)⁰ and Ω_c⁢(3327)⁰, are observed in the $$Ξ^{+}_{c}$$K^- invariant-mass spectrum using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb^-1. Five previously observed excited $$Ω^{0}_{c}$$ states are confirmed, namely Ω_c⁢(3000)⁰, Ω_c⁢(3050)⁰, Ω_c⁢(3065)⁰, Ω_c⁢(3090)⁰, and Ω_c⁢(3119)⁰. The masses and widths of these seven states are measured with the highest precision to date.

An amplitude analysis of $B^0$ → $J/$$$$\psi$$$$\phi$$$$K_S^0$$ decays is performed using proton-proton collision data, corresponding to an integrated luminosity of 9 fb^–1, collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. Evidence with a significance of 4.0 standard deviations of a structure in the $J/$$$$\psi$$$$K_S^0$$ system, named $$T_{ψs1}^{θ}$$⁢⁢(4000)⁰, is seen, with its mass and width measured to be 3991$$_{–10 –17}^{+12 +9}$$ MeV/⁢c² and 105$$_{–25 –23}^{+29 +17}$$ MeV, respectively, where the first uncertainty is statistical and the second systematic. The $$T_{ψs1}^{θ}$$⁢⁢(4000)⁰ state is likely to be the isospin partner of the $$T_{ψs1}^{θ}$$⁢⁢(4000)⁺ state, previously observed inmore » the $J/ψK^+$ system of the $B^+$$→$$J/ψ$$$$\phi$$$$K^+$ decay. When isospin symmetry for the charged and neutral $$T_{ψs1}^{θ}$$⁢⁢(4000) states is assumed, the signal significance increases to 5.4 standard deviations.« less

The ratios of branching fractions $R(D*)$ ≡ $$B(\overline{B} → D*τ^-\overline{ν}_μ$$)/$$B$$($$\overline{B}$$ → $$D*μ^-\overline{ν}_μ$$) and $$R$$($$D$$⁰) ≡ $$B$$($$B$$^- → $$D^0τ^-\overline{v}_τ$$)/$$B$$($$B$$^- → $$D^0μ^-\overline{v}_μ$$) are measured, assuming isospin symmetry, using a sample of proton-proton collision data corresponding to 3.0 fb^-1 of integrated luminosity recorded by the LHCb experiment during 2011 and 2012. The tau lepton is identified in the decay mode $τ^-$ → $$μ^-ν_τ\overline{ν}_μ$$. The measured values are $$R$$($$D$$*) = 0.281 ± 0.018 ± 0.024 and $$R$$($$D$$⁰) = 0.441 ± 0.060 ± 0.066, where the first uncertainty is statistical and the second is systematic. The correlation between these measurements is $$ρ$$ = -0.43. Themore » results are consistent with the current average of these quantities and are at a combined 1.9 standard deviations from the predictions based on lepton flavor universality in the standard model.« less

Searches for the rare hadronic decays $$B^0 → p\bar{p}p\bar{p}$$ and $$B^0_S → p\bar{p}p\bar{p}$$ are performed using proton-proton collision data recorded by the LHCb experiment and corresponding to an integrated luminosity of 9 fb^–1. Significances of 9.3⁢σ and 4.0⁢σ, including statistical and systematic uncertainties, are obtained for the $$B^0 → p\bar{p}p\bar{p}$$ and $$B^0_S → p\bar{p}p\bar{p}$$ signals, respectively. The branching fractions are measured relative to the topologically similar normalization decays B⁰ → J/ψ⁢(→ $$p\bar{p}$$)⁢K*⁰⁡(→ K⁺⁡π^–) and B$$^0_s$$→J/ψ⁢(→ $$p\bar{p}$$)$$\phi$$(→K⁺⁢K^–). The branching fractions are measured to be $$\mathcal{B}(B^0 → p\bar{p}p\bar{p})$$ = (2.2 ± 0.4 ± 0.1 ± 0.1)×10^–8 and $$\mathcal{B}(B^0_S → p\bar{p}p\bar{p})$$ = (2.3more » ± 1.0 ± 0.2 ± 0.1)×10^–8. In these measurements, the first uncertainty is statistical, the second is systematic, and the third one is due to the external branching fraction of the normalization channel.« less

A study of the B⁺ → $$K^0_S$$K⁺K^-π⁺ and B⁺ → $$K^0_S$$K⁺K⁺π^- decays is performed using proton-proton collisions at center-of-mass energies of 7, 8 and 13 TeV at the LHCb experiment. The $$K^0_S$$Kπ invariant mass spectra from both decay modes reveal a rich content of charmonium resonances. New precise measurements of the η_c and η_c(2S) resonance parameters are performed and branching fraction measurements are obtained for B⁺ decays to η_c, J/ψ, η_c(2S) and χ_c1 resonances. In particular, the first observation and branching fraction measurement of B⁺ → χ_c0K⁰π⁺ is reported as well as first measurements of the B⁺ → K⁰K⁺K^-π⁺ andmore » B⁺ → K⁰K⁺K^-π⁺ branching fractions. Dalitz plot analyses of η_c → $$K^0_S$$Kπ and η_c(2S) → $$K^0_S$$Kπ decays are performed. A new measurement of the amplitude and phase of the Kπ S-wave as functions of the Kπ mass is performed, together with measurements of the $$K^*_0$$(1430), $$K^*_0$$(1950) and a₀(1700) parameters. Finally, the branching fractions of χ_c1 decays to K* resonances are also measured.« less

An amplitude analysis of the B⁺ → $$D^{+}_{s}$$ $$D^{-}_{s}$$ ⁢K⁺ decay is carried out to study for the first time its intermediate resonant contributions, using proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. A near-threshold peaking structure, referred to as X⁡(3960), is observed in the $$D^{+}_{s}$$ $$D^{-}_{s}$$ invariant-mass spectrum with significance greater than 12 standard deviations. The mass, width, and the quantum numbers of the structure are measured to be 3956 ± 5 ± 10 MeV, 43 ± 13 ± 8 MeV, and J^P⁢C = 0⁺⁺, respectively, where the first uncertaintiesmore » are statistical and the second systematic. The properties of the new structure are consistent with recent theoretical predictions for a state composed of c$$\overline{c}$$s$$\overline{s}$$ quarks. Evidence for an additional structure is found around 4140 MeV in the $$D^{+}_{s}$$ $$D^{-}_{s}$$ invariant mass, which might be caused either by a new resonance with the 0⁺⁺ assignment or by a J/ψ⁢Φ ↔ $$D^{+}_{s}$$ $$D^{-}_{s}$$ coupled-channel effect.« less

The production rate of $$B^{0}_{s}$$ mesons relative to $B^0$ mesons is measured by the LHCb experiment in $pp$ collisions at a center-of-mass energy $$\sqrt{s}$$ = 13 TeV over the forward rapidity interval 2 < $$y$$ < 4.5 as a function of the charged particle multiplicity measured in the event. Evidence at the 3.4$$σ$$ level is found for an increase of the ratio of $$B^{0}_{s}$$ to $B^0$ cross sections with multiplicity at transverse momenta below 6 GeV /$$c$$, with no significant multiplicity dependence at higher transverse momentum. Comparison with data from $e^+$ $e^–$ collisions implies that the density of the hadronicmore » medium may affect the production rates of $$B$$ mesons. This is qualitatively consistent with the emergence of quark coalescence as an additional hadronization mechanism in high-multiplicity collisions.« less