65 Search Results

The branching fraction ratios of ${\overline{B}}^0\to D^{+}{\tau }^{-}{\overline{\nu }}_{\tau }$ and ${\overline{B}}^0\to D^{*+}{\tau }^{-}{\stackrel{¯more »}{\nu }}_{}$ τ decays are measured with respect to their muonic counterparts, using a data sample corresponding to an integrated luminosity of $2.0{\mathrm{fb}}^{-1}$ collected by the LHCb experiment in proton-proton collisions at $\sqrt{s}=13\mathrm{TeV}$ . The reconstructed final states are formed by combining $D^{+}$ mesons with ${\tau }^{-}\to {\mu }^{-}{\overline{\nu }}_{\mu }{\nu }_{\tau }$ candidates, where the $D^{+}$ is reconstructed via the $D^{+}\to K^{-}{\pi }^{+}{\pi }^{+}$ decay. The results are $R\left(D^{+}\right)=0.249\pm 0.043\pm 0.047$ , $R\left(D^{*+}\right)=0.402\pm 0.081\pm 0.085$ , where the first uncertainties are statistical and the second systematic. The two measurements have a correlation coefficient of $-0.39$ and are compatible with the standard model. © 2025 CERN, for the LHCb Collaboration 2025 CERN« less

The first study of $J/\psi \varphi$ production in diffractive processes in proton-proton collisions is presented. The study is based on an LHCb dataset recorded at center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $5{\mathrm{fb}}^{-1}$ . The data disfavor a nonresonant $J/\psi \varphi$ production but are consistent with a resonant model including several resonant states observed previously only in $B^{+}\to J/\psi \varphi K^{+more »}$ decays. The ${\chi }_{c0}\left(4500\right)$ state is observed with a significance over $6\sigma$ and the ${\chi }_{c1}\left(4274\right)$ is confirmed with a significance of more than $4\sigma$ . © 2025 CERN, for the LHCb Collaboration 2025 CERN« less

A comprehensive study of the angular distributions in the bottom-baryon decays ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{h}^{-}(h=\pi ,K)$ , followed by ${\mathrm{\Lambda }}_c^{+}\to \mathrm{\Lambda }{h}^{+}$ with $\mathrm{\Lambda }\to p{\pi }^{-}$ or ${\mathrm{\Lambda }}_c^{+}\to p{K}_{\mathrm{S}}^0$ decays, is performed using a data sample of proton-proton collisions corresponding to an integrated luminosity of $more »$ 9     fb − 1 collected by the LHCb experiment at center-of-mass energies of 7, 8, and 13 TeV. The decay parameters and the associated charge-parity ( $CP$ ) asymmetries are measured, with no significant $CP$ violation observed. For the first time, the ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{h}^{-}$ decay parameters are measured. The most precise measurements of the decay parameters $\alpha$ , $\beta$ , and $\gamma$ are obtained for ${\mathrm{\Lambda }}_c^{+}$ decays and an independent measurement of the decay parameters for the strange-baryon $\mathrm{\Lambda }$ decay is provided. The results deepen our understanding of weak decay dynamics in baryon decays. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

A search for violation of the charge-parity ( $CP$ ) symmetry in the $D^{+}\to K^{-}{K}^{+}{\pi }^{+}$ decay is presented, with proton-proton collision data corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ , collected at a center-of-mass energy of 13 TeV with the LHCb detector. A novel model-independent technique is used to compare the $D^{+}$ and $D^{-}$ phase-space distributions, with instrumental asymmetries subtractedmore » using the $D_s^{+}\to K^{-}{K}^{+}{\pi }^{+}$ decay as a control channel. The $p$ value for the hypothesis of $CP$ conservation is 8.1%. The $CP$ asymmetry observables $A_{CP|S}^{\varphi {\pi }^{+}}=(0.95\pm 0.43_{\mathrm{stat}}\pm 0.26_{\mathrm{syst}})\times {10}^{-3}$ and $A_{CP|S}^{{\overline{K}}^{*0}{K}^{+}}=(-0.26\pm 0.56_{\mathrm{stat}}\pm 0.18_{\mathrm{syst}})\times {10}^{-3}$ are also measured. These results show no evidence of $CP$ violation and represent the most sensitive search performed through the phase space of a multibody decay. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

The longitudinal polarization fraction of the $D^{*}$ meson is measured in $B^0\to D^{*-}{\tau }^{+}{\nu }_{\tau }$ decays, where the $\tau$ lepton decays to three charged pions and a neutrino, using proton-proton collision data collected by the LHCb experiment at center-of-mass energies of 7, 8 and 13 TeV and corresponding to an integrated luminosity of $5{\mathrm{fb}}^{-1}$ . The $D^{more »}$ * polarization fraction $F_L^{D^{*}}$ is measured in two $q^2$ regions, below and above $7{\mathrm{GeV}}^2/c^4$ , where $q^2$ is defined as the squared invariant mass of the $\tau {\nu }_{\tau }$ system. The $F_L^{D^{*}}$ values are measured to be $0.52\pm 0.07\pm 0.04$ and $0.34\pm 0.08\pm 0.02$ for the lower and higher $q^2$ regions, respectively. The first uncertainties are statistical and the second systematic. The average value over the whole $q^2$ range is $F_L^{D^{*}}=0.41\pm 0.06\pm 0.03$ . These results are compatible with the Standard Model predictions. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

A search for the lepton-flavor violating decays $B_s^0\to \varphi {\mu }^{\pm }{\tau }^{\mp }$ is presented, using a sample of proton-proton collisions at center-of-mass energies of 7, 8, and 13 TeV, collected with the LHCb detector and corresponding to a total integrated luminosity of $9{\mathrm{fb}}^{-1}$ . The $\tau$ leptons are selected using decays with three charged pions. No significant excess is observed, and an upper limit on the branching fraction is determined to be $\mathcal{B}more »$ ( B s 0 → ϕ μ ± τ ∓ ) < 1.0 × 10 − 5 at 90% confidence level. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

A sample of $pp$ collision data, corresponding to an integrated luminosity of $5.5{\mathrm{fb}}^{-1}$ and collected by the LHCb experiment during LHC Run 2, is used to measure the ratio of the lifetime of the ${\mathrm{\Xi }}_b^{-}$ baryon to that of the ${\mathrm{\Lambda }}_b^0$ baryon, $r_{\tau }\equiv {\tau }_{{\mathrm{\Xi }}_b^{-}}/{\tau }_{{\mathrm{\Lambda }}_b^0}$ . The value $more »$ r τ = 1.076 ± 0.013 ± 0.006 is obtained, where the first uncertainty is statistical and the second systematic. This value is averaged with the corresponding value from Run 1 to obtain $r_{\tau }^{\mathrm{Run}1,2}=1.078\pm 0.012\pm 0.007$ . Multiplying by the world-average value of the ${\mathrm{\Lambda }}_b^0$ lifetime yields ${\tau }_{{\mathrm{\Xi }}_b^{-}}^{\mathrm{Run}1,2}=1.578\pm 0.018\pm 0.010\pm 0.011\mathrm{ps}$ , where the uncertainties are statistical, systematic, and due to the limited knowledge of the ${\mathrm{\Lambda }}_b^0$ lifetime. This measurement improves the precision of the current world average of the ${\mathrm{\Xi }}_b^{-}$ lifetime by about a factor of 2, and is in good agreement with the most recent theoretical predictions. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

A search for the nonresonant ${\mathrm{\Lambda }}_c^{+}\to p{\mu }^{+}{\mu }^{-}$ decay is performed using proton-proton collision data recorded at a center-of-mass energy of 13 TeV by the LHCb experiment, corresponding to an integrated luminosity of $5.4{\mathrm{fb}}^{-1}$ . No evidence for the decay is found in the dimuon invariant-mass regions where the expected contributions of resonances is subdominant. The upper limit on the branching fraction of the ${\mathrm{\Lambda }}_c^{+}more »$ → p μ + μ − decay is determined to be $2.9\left(3.2\right)\times {10}^{-8}\text{at}90\%(95\%)$ confidence level. The branching fractions in the dimuon invariant-mass regions dominated by the $\eta$ , $\rho$ and $\omega$ resonances are also determined. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

A study of resonant structures in 𝐵⁺→𝐷*^+⁢𝐷⁻⁢𝐾⁺ and 𝐵⁺→𝐷*^−⁢𝐷⁺⁢𝐾⁺ decays is performed, using proton-proton collision data at center-of-mass energies of √𝑠 =7, 8, and 13 TeV recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb⁻¹. A simultaneous amplitude fit is performed to the two channels with contributions from resonances decaying to 𝐷*⁻⁢𝐷⁺ and 𝐷*⁺⁢𝐷⁻ states linked by 𝐶 parity. This procedure allows the 𝐶 parities of resonances in the 𝐷*^±⁢𝐷^∓ mass spectra to be determined. Four charmonium or charmoniumlike states are observed decaying into 𝐷*^±⁢𝐷^∓: 𝜂_𝑐⁡(3945), ℎ_𝑐⁡(4000), 𝜒_𝑐⁢1⁡(4010), and ℎ_𝑐⁡(4300), with quantum numbers 𝐽^𝑃⁢𝐶 equal tomore » 0⁻⁺, 1⁺⁻, 1⁺⁺, and 1⁺⁻, respectively. At least three of these states have not been observed previously. In addition, the existence of the 𝑇$$^*_{\bar{c}\bar{s}0}$$⁢(2870)⁰ and 𝑇$$^*_{\bar{c}\bar{s}1}$$(2900)⁰ resonances in the 𝐷⁻⁢𝐾⁺ mass spectrum, already observed in the 𝐵⁺→𝐷⁺⁢𝐷⁻⁢𝐾⁺ decay, is confirmed in a different production channel.« less

A measurement of time-dependent $CP$ violation in $D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decays using a $pp$ collision data sample collected by the LHCb experiment in 2012 and from 2015 to 2018, corresponding to an integrated luminosity of $7.7{\mathrm{fb}}^{-1}$ , is presented. The initial flavor ofmore » each $D^0$ candidate is determined from the charge of the pion produced in the $D^{*}(2010{)}^{+}\to D^0{\pi }^{+}$ decay. The decay $D^0\to K^{-}{\pi }^{+}{\pi }^0$ is used as a control channel to validate the measurement procedure. The gradient of the time-dependent $CP$ asymmetry $\mathrm{\Delta }Y$ in $D^0\to {\pi }^{+}{\pi }^{-}{\pi }^0$ decays is measured to be $\mathrm{\Delta }Y=(-1.3\pm 6.3\pm 2.4)\times {10}^{-4},$ where the first uncertainty is statistical and the second is systematic, which is compatible with $CP$ conservation. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less