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

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 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

The production of prompt $D_s^{+}$ and $D^{+}$ mesons is measured by the LHCb experiment in proton-lead ( $p\mathrm{Pb}$ ) collisions in both the forward ( $1.5<y^{*}<4.0$ ) and backward ( $-5.0<y^{*}<-2.5$ ) rapidity regions at a nucleon-nucleon center-of-mass energy of $\sqrt{s_{\mathrm{NN}}}=8.16\mathrm{TeV}$ .more » The nuclear modification factors of both $D_s^{+}$ and $D^{+}$ mesons are determined as a function of transverse momentum, $p_{\mathrm{T}}$ , and rapidity. In addition, the $D_s^{+}$ to $D^{+}$ cross section ratio is measured as a function of the primary charged particle multiplicity in the event. An enhanced $D_s^{+}$ to $D^{+}$ production in high-multiplicity events is observed for the whole measured $p_{\mathrm{T}}$ range, in particular at low $p_{\mathrm{T}}$ and backward rapidity, where the significance exceeds six standard deviations. This constitutes the first observation of strangeness enhancement in charm quark hadronization in high-multiplicity $p\mathrm{Pb}$ collisions. The results are also qualitatively consistent with the presence of quark coalescence as an additional charm quark hadronization mechanism in high-multiplicity proton-lead collisions. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

The four decays, ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Sigma }}_c^{(*)++}{D}^{(*)-}{K}^{-}$ , are observed for the first time using proton-proton collision data collected with the LHCb detector at a center-of-mass energy of 13 TeV, corresponding to an integrated luminosity of $6{\mathrm{fb}}^{-1}$ . By considering the ${\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{\stackrel{}{more »}}^{}$ D ¯ 0 K − decay as reference channel, the following branching fraction ratios are measured to be $\frac{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Sigma }}_c^{++}{D}^{-}{K}^{-})}{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Lambda }}_c^{+}{\overline{D}}^0{K}^{-})}=0.282\pm 0.016\pm 0.016\pm 0.005$ , $\frac{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Sigma }}_c^{*++}{D}^{-}{K}^{-})}{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Sigma }}_c^{++}{D}^{-}{K}^{-})}=0.460\pm 0.052\pm 0.028$ , $\frac{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Sigma }}_c^{++}{D}^{*-}{K}^{-})}{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Sigma }}_c^{++}{D}^{-}{K}^{-})}=2.261\pm 0.202\pm 0.129\pm 0.046$ , $\frac{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Sigma }}_c^{*++}{D}^{*-}{K}^{-})}{\mathcal{B}({\mathrm{\Lambda }}_b^0\to {\mathrm{\Sigma }}_c^{++}{D}^{-}{K}^{-})}=0.896\pm 0.137\pm 0.066\pm 0.018$ , where the first uncertainties are statistical, the second are systematic, and the third are due to uncertainties in the branching fractions of intermediate particle decays. These initial observations mark the beginning of pentaquark searches in these modes, with more datasets to become available following the LHCb upgrade. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

A search for hidden-charm pentaquark states decaying to a range of ${\mathrm{\Sigma }}_c\overline{D}$ and ${\mathrm{\Lambda }}_c^{+}\overline{D}$ final states, as well as doubly charmed pentaquark states to ${\mathrm{\Sigma }}_{c}D$ and ${\mathrm{\Lambda }}_c^{+}D$ , is made using samples of proton-proton collision data corresponding to an integrated luminosity ofmore » $5.7{\mathrm{fb}}^{-1}$ recorded by the LHCb detector at $\sqrt{s}=13\mathrm{TeV}$ . Since no significant signals are found, upper limits are set on the pentaquark yields relative to that of the ${\mathrm{\Lambda }}_c^{+}$ baryon in the ${\mathrm{\Lambda }}_c^{+}\to p{K}^{-}{\pi }^{+}$ decay mode. The known pentaquark states are also investigated, and their signal yields are found to be consistent with zero in all cases. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

The LHCb Collaboration measures production of the exotic hadron ${\chi }_{c1}\left(3872\right)$ in proton-nucleus collisions for the first time. Comparison with the charmonium state $\psi \left(2S\right)$ suggests that the exotic ${\chi }_{c1}\left(3872\right)$ experiences different dynamics in the nuclear medium than conventional hadrons, and comparison with data from proton-proton collisions indicates that the presence of the nucleus may modify ${\chi }_{c1}\left(3872\right)$ production rates. This ismore » the first measurement of the nuclear modification factor of an exotic hadron. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

Flow harmonic coefficients, $v_n$ , which are the key to studying the hydrodynamics of the quark-gluon plasma (QGP) created in heavy-ion collisions, have been measured in various collision systems and kinematic regions and using various particle species. The study of flow harmonics in a wide pseudorapidity range is particularly valuable to understand the temperature dependence of the shear viscosity to entropy density ratio of the QGP. This paper presents the first LHCb results of the second- and the third-order flow harmonic coefficients of charged hadrons as a function of transverse momentum in the forward region,more » corresponding to pseudorapidities between 2.0 and 4.9, using the data collected from PbPb collisions in 2018 at a center-of-mass energy of 5.02 $\text{TeV}$ . The coefficients measured using the two-particle angular correlation analysis method are smaller than the central-pseudorapidity measurements at ALICE and ATLAS from the same collision system but share similar features. ©2024 CERN, for the LHCb Collaboration 2024 CERN« less

An amplitude analysis of the $B^0\to K^{*0}{\mu }^{+}{\mu }^{-}$ decay is presented. The analysis is based on data collected by the LHCb experiment from proton-proton collisions at $\sqrt{s}=7$ , 8 and 13 TeV, corresponding to an integrated luminosity of $4.7{\mathrm{fb}}^{-1}$ . For the first time, Wilson coefficients and nonlocal hadronic contributions are accessed directly from the unbinned data, where the latter are parametrized asmore » a function of $q^2$ with a polynomial expansion. Wilson coefficients and nonlocal hadronic parameters are determined under two alternative hypotheses: the first relies on experimental information alone, while the second one includes information from theoretical predictions for the nonlocal contributions. Both models obtain similar results for the parameters of interest. The overall level of compatibility with the Standard Model is evaluated to be between 1.8 and 1.9 standard deviations when looking at the ${\mathcal{C}}_9$ Wilson coefficient alone, and between 1.3 and 1.4 standard deviations when considering the full set of ${\mathcal{C}}_9,{\mathcal{C}}_{10},{\mathcal{C}}_9^{\prime }$ and ${\mathcal{C}}_{10}^{\prime }$ Wilson coefficients. The ranges reflect the theoretical assumptions made in the analysis. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less

An amplitude analysis of the $B^0\to K^{*0}{\mu }^{+}{\mu }^{-}$ decay is presented using a dataset corresponding to an integrated luminosity of $4.7{\mathrm{fb}}^{-1}$ of $pp$ collision data collected with the LHCb experiment. For the first time, the coefficients associated to short-distance physics effects, sensitive to processes beyond the standardmore » model, are extracted directly from the data through a $q^2$ -unbinned amplitude analysis, where $q^2$ is the ${\mu }^{+}{\mu }^{-}$ invariant mass squared. Long-distance contributions, which originate from nonfactorizable QCD processes, are systematically investigated, and the most accurate assessment to date of their impact on the physical observables is obtained. The pattern of measured corrections to the short-distance couplings is found to be consistent with previous analyses of $b$ - to $s$ -quark transitions, with the largest discrepancy from the standard model predictions found to be at the level of 1.8 standard deviations. The global significance of the observed differences in the decay is 1.4 standard deviations. © 2024 CERN, for the LHCb Collaboration 2024 CERN« less