508 Search Results

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 $B^{+}\to J/\psi \varphi K^{+}$ 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

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 $9{\mathrm{fb}}^{-1}$ 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

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 subtracted 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

We report an improved measurement of the valence u and d quark distributions from the forward backward asymmetry in the Drell-Yan process using 8.6 fb^-1 of data collected with the D0 detector in $$p\overline{p}$$ collisions at $$\sqrt{s}$$ = 1.96. This analysis provides the values of new structure parameters that are directly related to the valence up and down quark distributions in the proton. In other experimental results measuring the quark content of the proton, d quark contributions are mixed with those from other quark flavors. In this measurement, the u and d quark contributions are separately extracted by applying a factorization of the QCD and electroweak portions of the forward-backward asymmetry.

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 $D^{*}$ 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

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 $\mathcal{B}(B_s^0\to \varphi {\mu }^{\pm }{\tau }^{\mp })<1.0\times {10}^{-5}$ at 90% confidence level. © 2024 CERN, for the LHCb Collaboration 2024 CERN

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 $r_{\tau }=1.076\pm 0.013\pm 0.006$ 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

A study of resonant structures in $B^{+}\to D^{*+}{D}^{-}{K}^{+}$ and $B^{+}\to D^{*-}{D}^{+}{K}^{+}$ decays is performed, using proton-proton collision data at center-of-mass energies of $\sqrt{s}=7$ , 8, and 13 TeV recorded by the LHCb experiment, corresponding to an integrated luminosity of $9{\mathrm{fb}}^{-1}$ . 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 $D^{*\pm }{D}^{\mp }$ mass spectra to be determined. Four charmonium or charmoniumlike states are observed decaying into $D^{*\pm }{D}^{\mp }$ : ${\eta }_c\left(3945\right)$ , $h_c\left(4000\right)$ , ${\chi }_{c1}\left(4010\right)$ , and $h_c\left(4300\right)$ , with quantum numbers $J^{PC}$ equal to $0^{-+}$ , $1^{+-}$ , $1^{++}$ , and $1^{+-}$ , respectively. At least three of these states have not been observed previously. In addition, the existence of the $T_{\overline{c}\overline{s}0}^{*}(2870{)}^0$ and $T_{\overline{c}\overline{s}1}^{*}(2900{)}^0$ resonances in the $D^{-}{K}^{+}$ mass spectrum, already observed in the $B^{+}\to D^{+}{D}^{-}{K}^{+}$ decay, is confirmed in a different production channel. © 2024 CERN, for the LHCb Collaboration 2024 CERN

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 ${\mathrm{\Lambda }}_c^{+}\to p{\mu }^{+}{\mu }^{-}$ 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

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 of 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