The LHCb collaboration measures production of the exotic hadron $\chi_{c1}$(3872) in proton-nucleus collisions for the first time. Comparison with the charmonium state $\psi$(2$S$) suggests that the exotic $\chi_{c1}$(3872) 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 $\chi_{c1}$(3872) production rates. This is the first measurement of the nuclear modification factor of an exotic hadron.

The decay-time-dependent CP asymmetry in Bs0→J/ψ(→μ+μ−)K+K− decays is measured using proton-proton collision data, corresponding to an integrated luminosity of 6 fb−1, collected with the LHCb detector at a center-of-mass energy of 13 TeV. Using a sample of approximately 349 000 Bs0 signal decays with an invariant K+K− mass in the vicinity of the ϕ(1020) resonance, the CP-violating phase ϕs is measured, along with the difference in decay widths of the light and heavy mass eigenstates of the Bs0−B¯s0 system, ΔΓs, and the difference of the average Bs0 and B0 meson decay widths, Γs−Γd. The values obtained are ϕs=−0.039±0.022±0.006 rad, ΔΓs=0.0845±0.0044±0.0024 ps−1, and Γs−Γd=−0.056−0.0015+0.0013±0.0014 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 ϕs is also measured independently for each polarization state of the K+K− system and shows no evidence for polarization dependence.Received 4 August 2023Accepted 4 December 2023DOI:https://doi.org/10.1103/PhysRevLett.132.051802Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article’s title, journal citation, and DOI. Funded by SCOAP3.© 2024 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Research AreasCabibbo–Kobayashi–Maskawa matrixElectroweak interactionParticle mixing & oscillationsQuark mixingPropertiesCP symmetryFlavor symmetriesParticles & Fields

The production rate of Λ 0 b baryons relative to B 0 mesons in pp collisions at a center-of-mass energy √ s = 13 TeV is measured by the LHCb experiment.The ratio of Λ 0 b to B 0 production cross-sections shows a significant dependence on both the transverse momentum and the measured charged-particle multiplicity.At low multiplicity, the ratio measured at LHCb is consistent with the value measured in e + e -collisions, and increases by a factor of ∼ 2 with increasing multiplicity.At relatively low transverse momentum, the ratio of Λ 0 b to B 0 cross-sections is higher than what is measured in e + e -collisions, but converges with the e + e -ratio as the momentum increases.These results imply that the evolution of heavy b quarks into final-state hadrons is influenced by the density of the hadronic environment produced in the collision.Comparisons with several models and implications for the mechanisms enforcing quark confinement are discussed.

The four decays, Λb0→Σc(*)++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 fb−1. By considering the Λb0→Λc+D¯0K− decay as reference channel, the following branching fraction ratios are measured to be B(Λb0→Σc++D−K−)B(Λb0→Λc+D¯0K−)=0.282±0.016±0.016±0.005, B(Λb0→Σc*++D−K−)B(Λb0→Σc++D−K−)=0.460±0.052±0.028, B(Λb0→Σc++D*−K−)B(Λb0→Σc++D−K−)=2.261±0.202±0.129±0.046, B(Λb0→Σc*++D*−K−)B(Λb0→Σc++D−K−)=0.896±0.137±0.066±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

The fraction of χc1 and χc2 decays in the prompt J/ψ yield, Fχc→J/ψ=σχc→J/ψ/σJ/ψ, is measured by the LHCb detector in pPb collisions at sNN=8.16 TeV. The study covers the forward (1.5

The production of prompt D0 mesons in proton-lead collisions in both the forward and backward rapidity regions at a center-of-mass energy per nucleon pair of √sNN=8.16 TeV is measured by the LHCb experiment. The nuclear modification factor of prompt D0 mesons is determined as a function of the transverse momentum pT, and the rapidity in the nucleon-nucleon center-of-mass frame y∗. In the forward rapidity region, significantly suppressed production with respect to pp collisions is measured, which provides significant constraints on models of nuclear parton distributions and hadron production down to the very low Bjorken-x region of ∼10−5. In the backward rapidity region, a suppression with a significance of 2.0–3.8 standard deviations compared to parton distribution functions in a nuclear environment expectations is found in the kinematic region of pT>6 GeV/c and −3.25

The first observation and study of two new baryonic structures in the final state ${\mathrm{\ensuremath{\Xi}}}_{b}^{0}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ and the confirmation of the ${\mathrm{\ensuremath{\Xi}}}_{b}{(6100)}^{\ensuremath{-}}$ state in the ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}$ decay mode are reported using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of $9\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. In addition, the properties of the known ${\mathrm{\ensuremath{\Xi}}}_{b}^{*0}$, ${\mathrm{\ensuremath{\Xi}}}_{b}^{\ensuremath{'}\ensuremath{-}}$ and ${\mathrm{\ensuremath{\Xi}}}_{b}^{*\ensuremath{-}}$ resonances are measured with improved precision. The new decay mode of the ${\mathrm{\ensuremath{\Xi}}}_{b}^{0}$ baryon to the ${\mathrm{\ensuremath{\Xi}}}_{c}^{+}$ ${\ensuremath{\pi}}^{\ensuremath{-}}$ ${\ensuremath{\pi}}^{+}$ ${\ensuremath{\pi}}^{\ensuremath{-}}$ final state is observed and exploited for the first time in these measurements.

The production of $\eta$ and $\eta'$ mesons is studied in proton-proton and proton-lead collisions collected with the LHCb detector. Proton-proton collisions are studied at center-of-mass energies of $5.02$ and $13~{\rm TeV}$, and proton-lead collisions are studied at a center-of-mass energy per nucleon of $8.16~{\rm TeV}$. The studies are performed in center-of-mass rapidity regions $2.5

Searches for the rare hadronic decays B^{0}→pp[over ¯]pp[over ¯] and B_{s}^{0}→pp[over ¯]pp[over ¯] are performed using proton-proton collision data recorded by the LHCb experiment and corresponding to an integrated luminosity of 9 fb^{-1}. Significances of 9.3σ and 4.0σ, including statistical and systematic uncertainties, are obtained for the B^{0}→pp[over ¯]pp[over ¯] and B_{s}^{0}→pp[over ¯]pp[over ¯] signals, respectively. The branching fractions are measured relative to the topologically similar normalization decays B^{0}→J/ψ(→pp[over ¯])K^{*0}(→K^{+}π^{-}) and B_{s}^{0}→J/ψ(→pp[over ¯])⁢ϕ(→K^{+}K^{-}). The branching fractions are measured to be B(B^{0}→pp[over ¯]pp[over ¯])=(2.2±0.4±0.1±0.1)×10^{-8} and B(B_{s}^{0}→pp[over ¯]pp[over ¯])=(2.3±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.

Resonant structures in the dipion mass spectrum from ${\ensuremath{\chi}}_{c1}(3872)\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}J/\ensuremath{\psi}$ decays, produced via ${B}^{+}\ensuremath{\rightarrow}{K}^{+}{\ensuremath{\chi}}_{c1}(3872)$ decays, are analyzed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of $9\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. A sizeable contribution from the isospin conserving ${\ensuremath{\chi}}_{c1}(3872)\ensuremath{\rightarrow}\ensuremath{\omega}J/\ensuremath{\psi}$ decay is established for the first time, $(21.4\ifmmode\pm\else\textpm\fi{}2.3\ifmmode\pm\else\textpm\fi{}2.0)%$, with a significance of more than $7.1\ensuremath{\sigma}$. The amplitude of isospin violating decay, ${\ensuremath{\chi}}_{c1}(3872)\ensuremath{\rightarrow}{\ensuremath{\rho}}^{0}J/\ensuremath{\psi}$, relative to isospin conserving decay, ${\ensuremath{\chi}}_{c1}(3872)\ensuremath{\rightarrow}\ensuremath{\omega}J/\ensuremath{\psi}$, is properly determined, and it is a factor of 6 larger than expected for a pure charmonium state.

AbstractThe first study of$$C\!P$$CPviolation in the decay mode$${{B} ^\pm } \rightarrow [{{K} ^+} {{K} ^-} {{\uppi } ^+} {{\uppi } ^-} ]_{D} h^\pm $$B±→[K+K-π+π-]Dh±, with$$h=K,\pi $$h=K,π, is presented, exploiting a data sample of proton–proton collisions collected by the LHCb experiment that corresponds to an integrated luminosity of$$9\text {\,fb} ^{-1} $$9\,fb-1. The analysis is performed in bins of phase space, which are optimised for sensitivity to local$$C\!P$$CPasymmetries.$$C\!P$$CP-violating observables that are sensitive to the angle$$\gamma $$γof the Unitarity Triangle are determined. The analysis requires external information on charm-decay parameters, which are currently taken from an amplitude analysis of LHCb data, but can be updated in the future when direct measurements become available. Measurements are also performed of phase-space integrated observables for$${{B} ^\pm } \rightarrow [{{K} ^+} {{K} ^-} {{\uppi } ^+} {{\uppi } ^-} ]_{D} h^\pm $$B±→[K+K-π+π-]Dh±and$${{B} ^\pm } \rightarrow [{{\uppi } ^+} {{\uppi } ^-} {{\uppi } ^+} {{\uppi } ^-} ]_{D} h^\pm $$B±→[π+π-π+π-]Dh±decays.

Resonant contributions in $B^0 \rightarrow \overline{D}^0 D^+_s\pi^-$ and $B^+\rightarrow D^- D^+_s\pi^+$ decays are determined with an amplitude analysis, which is performed both separately and simultaneously, where in the latter case isospin symmetry between the decays is assumed. The analysis is based on data collected by the LHCb detector in proton-proton collisions at center-of-mass energies of 7, 8 and 13 $\rm{TeV}$. The full data sample corresponds to an integrated luminosity of 9 $\rm fb^{-1}$. A doubly charged spin-0 open-charm tetraquark candidate together with a neutral partner, both with masses near $2.9\,\rm{GeV}$, are observed in the $D_s\pi$ decay channel.

The branching fraction $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\tau}}^{+}{\ensuremath{\nu}}_{\ensuremath{\tau}})$ is measured relative to that of the normalization mode ${B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ using hadronic ${\ensuremath{\tau}}^{+}\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}({\ensuremath{\pi}}^{0}){\overline{\ensuremath{\nu}}}_{\ensuremath{\tau}}$ decays in proton-proton collision data at a center-of-mass energy of 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of $2\text{ }\text{ }{\mathrm{fb}}^{\ensuremath{-}1}$. The measured ratio is $\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\tau}}^{+}{\ensuremath{\nu}}_{\ensuremath{\tau}})/\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+})=1.70\ifmmode\pm\else\textpm\fi{}0.1{0}_{\ensuremath{-}0.10}^{+0.11}$, where the first uncertainty is statistical and the second is related to systematic effects. Using established branching fractions for the ${B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{+}$ and ${B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}}$ modes, the lepton universality test $\mathcal{R}({D}^{*\ensuremath{-}})\ensuremath{\equiv}\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\tau}}^{+}{\ensuremath{\nu}}_{\ensuremath{\tau}})/\mathcal{B}({B}^{0}\ensuremath{\rightarrow}{D}^{*\ensuremath{-}}{\ensuremath{\mu}}^{+}{\ensuremath{\nu}}_{\ensuremath{\mu}})$ is calculated, $\mathcal{R}({D}^{*\ensuremath{-}})=0.247\ifmmode\pm\else\textpm\fi{}0.015\ifmmode\pm\else\textpm\fi{}0.015\ifmmode\pm\else\textpm\fi{}0.012$, where the third uncertainty is due to the uncertainties on the external branching fractions. This result is consistent with the Standard Model prediction and with previous measurements.

An amplitude analysis of the B+→D+sD−sK+ 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+sD−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 JPC=0++, respectively, where the first uncertainties are statistical and the second systematic. The properties of the new structure are consistent with recent theoretical predictions for a state composed of c¯cs¯s quarks. Evidence for an additional structure is found around 4140 MeV in the D+sD−s invariant mass, which might be caused either by a new resonance with the 0++ assignment or by a J/ψϕ↔D+sD−s coupled-channel effect.Received 28 October 2022Revised 6 February 2023Accepted 28 February 2023DOI:https://doi.org/10.1103/PhysRevLett.131.071901Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI. Funded by SCOAP3.© 2023 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Research AreasMultiquark bound statesParticle interactionsStrong interactionParticles & Fields

An amplitude analysis of B^{0}→J/ψϕK_{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/ψK_{S}^{0} system, named T_{ψs1}^{θ}(4000)^{0}, is seen, with its mass and width measured to be 3991_{-10}^{+12} _{-17}^{+9} MeV/c^{2} and 105_{-25}^{+29} _{-23}^{+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 in the J/ψK^{+} system of the B^{+}→J/ψϕK^{+} 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.

AbstractThe measurement of charmonium states produced in proton-neon ($$p\text {Ne}$$ p Ne ) collisions by the LHCb experiment in its fixed-target configuration is presented. The production of $${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$ J / ψ and $$\psi {(2S)}$$ ψ ( 2 S ) mesons is studied with a beam of 2.5$$\mathrm{\,Te\hspace{-1.00006pt}V}$$ Te V protons colliding on gaseous neon targets at rest, corresponding to a nucleon-nucleon centre-of-mass energy $$\sqrt{s_{\scriptscriptstyle \text {NN}}} =68.5\mathrm{\,Ge\hspace{-1.00006pt}V} $$ s NN = 68.5 Ge V . The data sample corresponds to an integrated luminosity of $$21.7\pm 1.4 $$ 21.7 ± 1.4 nb$$^{-1}$$ - 1 . The $${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$ J / ψ and $$\psi {(2S)}$$ ψ ( 2 S ) hadrons are reconstructed in $$\mu ^+$$ μ + $$\mu ^-$$ μ - final states. The $${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$ J / ψ production cross-section per target nucleon in the centre-of-mass rapidity range $$y^\star \in [-2.29, 0]$$ y ⋆ ∈ [ - 2.29 , 0 ] is found to be $$506 \pm 8 \pm 46 \text { nb/nucleon}$$ 506 ± 8 ± 46 nb/nucleon . The ratio of $${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$ J / ψ and $$D^0$$ D 0 cross-sections is evaluated to $$(1.06 \pm 0.02 \pm 0.09)\%$$ ( 1.06 ± 0.02 ± 0.09 ) % . The $$\psi {(2S)}$$ ψ ( 2 S ) to $${{J} \hspace{-1.66656pt}/\hspace{-1.111pt}\psi }$$ J / ψ relative production rate is found to be $$(1.67 \pm 0.27\pm 0.10)\%$$ ( 1.67 ± 0.27 ± 0.10 ) % in good agreement with other measurements involving beam and target nuclei of similar sizes.

AbstractThe first measurement of $${{J}/\psi }$$ J / ψ and $${{D}} ^0$$ D 0 production in PbNe collisions by the LHCb experiment in its fixed-target configuration is reported. The production of $${{J}/\psi }$$ J / ψ and $${{D}} ^0$$ D 0 mesons is studied with a beam of lead ions with an energy of 2.5$$\,\text {TeV}$$ TeV per nucleon colliding on gaseous neon targets at rest, corresponding to a nucleon-nucleon centre-of-mass energy of $$\sqrt{s_{\scriptscriptstyle \text {NN}}} =68.5\,\text {GeV} $$ s NN = 68.5 GeV . The $${{J}/\psi }$$ J / ψ /$${{D}} ^0$$ D 0 production cross-section ratio is studied as a function of rapidity, transverse momentum and collision centrality. These data are compared with measurements from $$p\text {Ne}$$ p Ne collisions at the same energy and show no difference in the observed $${{J}/\psi }$$ J / ψ suppression trend when comparing $$p\text {Ne}$$ p Ne and PbNe peripheral collisions with PbNe central collisions.

AbstractThe interpretation of cosmic antiproton flux measurements from space-borne experiments is currently limited by the knowledge of the antiproton production cross-section in collisions between primary cosmic rays and the interstellar medium. Using collisions of protons with an energy of 6.5$$\,\text {Te\hspace{-1.00006pt}V}$$ Te V incident on helium nuclei at rest in the proximity of the interaction region of the LHCb experiment, the ratio of antiprotons originating from antihyperon decays to prompt production is measured for antiproton momenta between 12 and $$110\,\text {Ge\hspace{-1.00006pt}V\!/}c $$ 110 Ge V\!/ c . The dominant antihyperon contribution, namely $${\overline{\varLambda }} \rightarrow {\overline{{p}}} {{\pi } ^+} $$ Λ ¯ → p ¯ π + decays from promptly produced $$\overline{\varLambda }$$ Λ ¯ particles, is also exclusively measured. The results complement the measurement of prompt antiproton production obtained from the same data sample. At the energy scale of this measurement, the antihyperon contributions to antiproton production are observed to be significantly larger than predictions of commonly used hadronic production models.

An amplitude analysis of $\Lambda^+_c \to pK^-\pi^+$ decays together with a measurement of the $\Lambda^+_c$ polarization vector in semileptonic beauty hadron decays is presented. A sample of $400\,000$ candidates is selected from proton-proton collisions recorded by the LHCb detector at a center-of-mass energy of 13 TeV. An amplitude model is developed and the resonance fractions as well as two- and three-body decay parameters are reported. The mass and width of the $\Lambda(2000)$ state are also determined. A significant $\Lambda^+_c$ polarization is found. A large sensitivity of the $\Lambda^+_c \to pK^-\pi^+$ decay to the polarization is seen, making the amplitude model suitable for $\Lambda^+_c$ polarization measurements in other systems.