The LHCb Ring-Imaging Cherenkov detectors are built to provide charged hadron identification over a large range of momentum. The upgraded detectors are also capable of providing an independent measurement of the luminosity for the LHCb experiment during LHC Run 3. The modelling of the opto-electronics chain, the application of the powering strategy during operations, the calibration procedures and the proof of principle of a novel technique for luminosity determination are presented. In addition, the preliminary precision achieved during the 2023 data-taking year for real-time and offline luminosity measurements is reported.

The kaon physics programme, long heralded as a cutting-edge frontier by the European Strategy for Particle Physics, continues to stand at the intersection of discovery and innovation in high-energy physics (HEP). With its unparalleled capacity to explore new physics at the multi-TeV scale, kaon research is poised to unveil phenomena that could reshape our understanding of the Universe. This document highlights the compelling physics case, with emphasis on exciting new opportunities for advancing kaon physics not only in Europe but also on a global stage. As an important player in the future of HEP, the kaon programme promises to drive transformative breakthroughs, inviting exploration at the forefront of scientific discovery.

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

Searches for Dark Matter with the NA62 and NA64 experiments at CERN are presented. In the NA62 experiment the search is in the decays $A^\prime \to \mu \mu$ and $A^\prime \to e e$, where $A^\prime$ is a new vector particle corresponding to a vector mediator field. The NA64 experiment looks for events with invisible decays of $A^\prime$ and thus having large missing energy. New upper limits have been set on models with such a vector mediator field.

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 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

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.

A search for rare $B \rightarrow D \mu^+ \mu^-$ decays is performed using proton-proton collision data collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb$^{-1}$. No significant signals are observed in the non-resonant $\mu^+\mu^-$ modes, and upper limits of $\mathcal{B}(B^0 \rightarrow \overline{D}^0 \mu^+ \mu^-) < 5.1 \times 10^{-8}$, $\mathcal{B}(B^+ \rightarrow D_s^+ \mu^+ \mu^-) < 3.2 \times 10^{-8}$, $\mathcal{B}(B_s^0 \rightarrow \overline{D}^0 \mu^+ \mu^-) < 1.6 \times 10^{-7}$ and $f_c/f_u \cdot \mathcal{B}(B_c^+ \rightarrow D_s^+ \mu^+ \mu^-) < 9.6 \times 10^{-8}$ are set at the 95\% confidence level, where $f_c$ and $f_u$ are the fragmentation fractions of a $B$ meson with a $c$ and $u$ quark respectively in proton-proton collisions. Each result is either the first such measurement or an improvement by three orders of magnitude on an existing limit. Separate upper limits are calculated when the muon pair originates from a $J/\psi \rightarrow \mu^+ \mu^-$ decay. The branching fraction of $B_c^+ \rightarrow D_s^+ J/\psi$ multiplied by the fragmentation-fraction ratio is measured to be $f_c/f_u \cdot \mathcal{B}(B_c^+ \rightarrow D_s^+ J/\psi ) = (1.63 \pm 0.15 \pm 0.13) \times 10^{-5}$, where the first uncertainty is statistical and the second systematic.

Tests of lepton universality in B^{0}→K_{S}^{0}ℓ^{+}ℓ^{-} and B^{+}→K^{*+}ℓ^{+}ℓ^{-} decays where ℓ is either an electron or a muon are presented. The differential branching fractions of B^{0}→K_{S}^{0}e^{+}e^{-} and B^{+}→K^{*+}e^{+}e^{-} decays are measured in intervals of the dilepton invariant mass squared. The measurements are performed using proton-proton collision data recorded by the LHCb experiment, corresponding to an integrated luminosity of 9 fb^{-1} . The results are consistent with the standard model and previous tests of lepton universality in related decay modes. The first observation of B^{0}→K_{S}^{0}e^{+}e^{-} and B^{+}→K^{*+}e^{+}e^{-} decays is reported.

An improved measurement of the decay B0s→μ+μ− and searches for the decays B0→μ+μ− and B0s→μ+μ−γ are performed at the LHCb experiment using data collected in proton-proton collisions at √s=7, 8 and 13 TeV, corresponding to integrated luminosities of 1, 2 and 6 fb−1, respectively. The B0s→μ+μ− branching fraction and effective lifetime are measured to be B(B0s→μ+μ−)=(3.09+0.46+0.15−0.43−0.11)×10−9 and τ(B0s→μ+μ−)=(2.07±0.29±0.03) ps, respectively, where the uncertainties include both statistical and systematic contributions. No significant signal for B0→μ+μ− and B0s→μ+μ−γ decays is found and the upper limits B(B0→μ+μ−)<2.6×10−10 and B(B0s→μ+μ−γ)<2.0×10−9 at 95% confidence level are determined, where the latter is limited to the range mμμ>4.9 GeV/c2. Additionally, the ratio between the B0→μ+μ− and B0s→μ+μ− branching fractions is measured to be Rμ+μ−<0.095 at 95% confidence level. The results are in agreement with the Standard Model predictions.10 MoreReceived 23 August 2021Accepted 8 December 2021DOI:https://doi.org/10.1103/PhysRevD.105.012010Published 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.© 2022 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Research AreasBranching fractionFlavor changing neutral currentsRare decaysPhysical SystemsBottom mesonsParticles & Fields

The first full angular analysis and an updated measurement of the decay-rate CP asymmetry of the D^{0}→π^{+}π^{-}μ^{+}μ^{-} and D^{0}→K^{+}K^{-}μ^{+}μ^{-} decays are reported. The analysis uses proton-proton collision data collected with the LHCb detector at center-of-mass energies of 7, 8, and 13 TeV. The dataset corresponds to an integrated luminosity of 9 fb^{-1}. The full set of CP -averaged angular observables and their CP asymmetries are measured as a function of the dimuon invariant mass. The results are consistent with expectations from the standard model and with CP symmetry.

The T -odd correlation ξ_π eγ , which is the mixed product of the momenta of e^ + , π^0 , and γ in the system of rest of the kaon divided by M_K^3 , has been measured in the K + → π 0 e + ν e γ radiative decay among 101 200 candidate events detected at the OKA setup. The asymmetry of the distribution in ξ_π eγ is characterized by the ratio A_ξ = N_ + - N_ - /N_ + + N_ - , where N_ + ( - ) is the number of events with positive (negative) ξ. The value A_ξ = (+0.1 ± 3.9(stat.) ± 1.7(syst.)) × 10 –3 or |A_ξ| < 5.4 ×10^ - 3 (90

An amplitude analysis of flavor-untagged B_{s}^{0}→J/ψpp[over ¯] decays is performed using a sample of 797±31 decays reconstructed with the LHCb detector. The data, collected in proton-proton collisions between 2011 and 2018, correspond to an integrated luminosity of 9 fb^{-1}. Evidence for a new structure in the J/ψp and J/ψp[over ¯] systems with a mass of 4337_{-4}^{+7} _{-2}^{+2} MeV and a width of 29_{-12}^{+26} _{-14}^{+14} MeV is found, where the first uncertainty is statistical and the second systematic, with a significance in the range of 3.1 to 3.7σ, depending on the assigned J^{P} hypothesis.

The first observation of the Ω−b→Ξ+cK−π− decay is reported using p p collision data at center of mass energies of 7, 8, and 13 TeV collected by the LHCb experiment, corresponding to an integrated luminosity of 9 fb−1. Four excited Ω0c baryons are observed in the Ξ+c K− mass projection of the Ω−b→Ξ+cK−π− decays with the significance of each exceeding five standard deviations. They coincide with the states previously observed in prompt pp and e+e− production. Relative production rates, masses, and natural widths of the states are measured, and a test of spin hypotheses is performed. Moreover, the branching ratio of Ω−b→Ξ+cK−π− is measured relative to the Ω−b→Ω0cπ− decay mode and a precise measurement of the Ω−b mass of 6044.3±1.2±1.1+0.19−0.22 MeV is obtained.Received 8 July 2021Accepted 14 September 2021DOI:https://doi.org/10.1103/PhysRevD.104.L091102Published 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.© 2021 CERN, for the LHCb CollaborationPhysics Subject Headings (PhySH)Hadron collidersTechniquesExperimental TechniquesParticle acceleratorsHadron collidersResearch AreasBranching fractionHadronic decaysPhysical SystemsBottom baryonsCharmed baryonsPropertiesMassParitySpinTechniquesHadron collidersParticles & Fields

Results of a study of the K^+ →π ^0 e^+νγ decay at OKA setup are presented. More than 32,000 events of this decay are observed. The differential spectra over the photon energy and the photon–electron opening angle in kaon rest frame are presented. The branching ratios, normalized to that of K_e3 decay are calculated for different cuts on E^*_γ and cosΘ ^*_eγ . In particular, the branching ratio for E^*_γ>30 MeV and Θ ^*_e γ>20^∘ is measured R = Br(K^+ →π ^0 e^+ν _eγ ) /Br(K^+ →π ^0 e^+ν _e) = = (0.587±0.010( stat .)±0.015( syst .)) × 10^-2 , which is in a good agreement with ChPT O(p^4) calculations.