A Large Ion Collider Experiment (ALICE) has been conceived and constructed as a heavy-ion experiment at the LHC. During LHC Runs 1 and 2, it has produced a wide range of physics results using all collision systems available at the LHC. In order to best exploit new physics opportunities opening up with the upgraded LHC and new detector technologies, the experiment has undergone a major upgrade during the LHC Long Shutdown 2 (2019–2022). This comprises the move to continuous readout, the complete overhaul of core detectors, as well as a new online event processing farm with a redesigned online-offline software framework. These improvements will allow to record Pb-Pb collisions at rates up to 50 kHz, while ensuring sensitivity for signals without a triggerable signature.

The measurement of charmonium states produced in proton-neon ( pNe ) collisions by the LHCb experiment in its fixed-target configuration is presented. The production of J/ψ and ψ(2S) mesons is studied with a beam of 2.5 TeV protons colliding on gaseous neon targets at rest, corresponding to a nucleon-nucleon centre-of-mass energy √(s_NN) =68.5 GeV . The data sample corresponds to an integrated luminosity of 21.7± 1.4 nb ^-1 . The J/ψ and ψ(2S) hadrons are reconstructed in μ ^+ μ ^- final states. The J/ψ production cross-section per target nucleon in the centre-of-mass rapidity range y^⋆∈ [-2.29, 0] is found to be 506 ± 8 ± 46 nb/nucleon . The ratio of J/ψ and D^0 cross-sections is evaluated to (1.06 ± 0.02 ± 0.09)% . The ψ(2S) to J/ψ relative production rate is found to be (1.67 ± 0.27± 0.10)% in good agreement with other measurements involving beam and target nuclei of similar sizes.

The decay B- -> Lambda(+)(c)(Lambda) over bar K--(c)- is studied in proton-proton collisions at a center-of-mass energy of root s = 13 TeV using data corresponding to an integrated luminosity of 5 fb(-1) collected by the LHCb experiment. In the Lambda K-+(c)- system, the Xi(c)(2930)(0) state observed at the BABAR and Belle experiments is resolved into two narrower states, Xi(c)(2923)(0) and Xi(c)(2939)(0), whose masses and widths are measured to be m(Xi(c)(2930)(0) = 2924.5 +/- 0.4 +/- 1.1 Mev, m Xi(c)(2930)(0)) = 2938.5 +/- 0.9 +/- 2.3 Mev, Gamma(Xi(c)(2930)(0)) = 4.8 +/- 0.9 +/- 1.5 MeV, Gamma(Xi(c)(2930)(0) - 11.0 +/- 1.9 +/- 7.5 MeV, where the first uncertainties are statistical and the second systematic. The results are consistent with a previous LHCb measurement using a prompt Lambda K-+(c)- sample. Evidence of a new Xi(c)(2930)(0) state is found with a local significance of 3.8 sigma, whose mass and width are measured to be 2881.8 +/- 3.1 +/- 8.5 MeV and 12.4 +/- 5.3 +/- 5.8 MeV, respectively. In addition, evidence of a new decay mode Xi(c)(2930)(0) -> Lambda K-+(c) is found with a significance of 3.7 sigma. The relative branching fraction of B- -> Lambda(+)(c)(Lambda) over bar K--(c)- with respect to the B- -> D+D-K- decay is measured to be 2.36 +/- 0.11 +/- 0.22 +/- 0.25, where the first uncertainty is statistical, the second systematic and the third originates from the branching fractions of charm hadron decays.

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

A first search for the lepton-flavour violating decays B-0 -> K*0 tau(+/-)mu -/+ is presented. The analysis is performed using a sample of proton-proton collision data, collected with the LHCb detector at centre-of-mass energies of 7, 8 and 13TeV between 2011 and 2018, corresponding to an integrated luminosity of 9 fb(-1). No significant signal is observed, and upper limits on the branching fractions are determined to be B(B-0 -> K*0 tau(+)mu(-)) < 1.0 (1.2) x 10(-5) and B(B-0 -> K*0 tau(-)mu(+)) < 8.2 (9.8) x 10(-6) at the 90% (95%) confidence level.

Abstract The 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.

We report on a measurement of the Lambda(+)(c) to D-0 production ratio in peripheral PbPb collisions at root sNN = 5.02TeV with the LHCb detector in the forward rapidity region 2 < y < 4.5. The Lambda(+)(c) (D-0) hadrons are reconstructed via the decay channel Lambda(+)(c) -> pK(-)pi(+) (D-0 -> K- pi(+)) for 2 < pT < 8 GeV/ c and in the centrality range of about 65-90%. The results show no significant dependence on pT, y or the mean number of participating nucleons. They are also consistent with similar measurements obtained by the LHCb collaboration in pPb and Pbp collisions at root sNN = 5.02TeV. The data agree well with predictions from PYTHIA in pp collisions at root s = 5TeV but are in tension with predictions of the Statistical Hadronization model.

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.

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.

A study of the B → KS0K+K-π+ and B → KS0K+K+π- decays is performed using proton-proton collisions at center-of-mass energies of 7, 8 and 13 TeV at the LHCb experiment. The KS0K±π± invariant mass spectra from both decay modes reveal a rich content of charmonium resonances, such as ηc, J/ψ, ηc(2S) and χc1. Precise measurements of their parameters and branching fractions are obtained. Dalitz plot analyses of ηc → KS0K±π± and ηc(2S) → KS0K±π± decays are performed.

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

A measurement of charm mixing and CP-violating parameters is reported, using B over bar -> D0(-> K0S pi+pi-)x mu- nu over bar mu X decays reconstructed in proton-proton collisions collected by the LHCb experiment during the years 2016 to 2018, corresponding to an integrated luminosity of 5.4 fb-1. The measured mixing and CP-violating parameters are xCP = [4.29 1 1.48(stat) 1 0.26(syst)] x 10-3, yCP = [12.61 1 3.12(stat) 1 0.83(syst)] x 10-3, Ax = [-0.77 1 0.93(stat) 1 0.28(syst)] x 10-3, Ay = [3.01 1 1.92(stat) 1 0.26(syst)] x 10-3. The results are complementary to and consistent with previous measurements. A combination with the recent LHCb analysis of D*+ -> D0(-> K0S pi+ pi-)pi+ decays is reported.

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.

Measurements of $CP$ asymmetry in charmless $B\to PV$ decays are presented, where $P$ and $V$ denote a pseudoscalar and a vector meson, respectively. Five different $B\to PV$ decays from four final states, $B^\pm \to \pi^\pm \pi^+ \pi^-$, $B^\pm \to K^\pm \pi^+ \pi^-$, $B^\pm \to K^\pm K^+ K^-$ and $B^\pm \to \pi^\pm K^+ K^-$ are analyzed. The measurements are based on a method that does not require full amplitude analyses, and are performed using proton-proton collision data at a center-of-mass energy of 13 TeV collected by LHCb between 2015 and 2018, corresponding to an integrated luminosity of 5.9 fb$^{-1}$. In the $\pi^+ \pi^-$ $\textit{P}$-wave, in the region dominated by the $B^\pm \to \rho(770)^0 K^\pm$ decay, a $CP$ asymmetry of $\mbox{$A_{CP}$ = +0.150 $\pm$ 0.019 $\pm$ 0.011}$ is measured, where the first uncertainty is statistical and the second is systematic. This is the first observation of $CP$ violation in this process. For the other four decay channels, in regions dominated by the $B^\pm \to \rho(770)^0 \pi^\pm$, $B^\pm \to \overset{(-)}{K^*}(892)^0 \pi^\pm$, $B^\pm \to \overset{(-)}{K^*}(892)^0 K^\pm$ and $B^\pm \to \phi(1020) K^\pm$ decays, $CP$ asymmetries in the $\textit{P}$-wave compatible with zero are measured.

The performance of the electromagnetic calorimeter of the ALICE experiment during operation in 2010–2018 at the Large Hadron Collider is presented. After a short introduction into the design, readout, and trigger capabilities of the detector, the procedures for data taking, reconstruction, and validation are explained. The methods used for the calibration and various derived corrections are presented in detail. Subsequently, the capabilities of the calorimeter to reconstruct and measure photons, light mesons, electrons and jets are discussed. The performance of the calorimeter is illustrated mainly with data obtained with test beams at the Proton Synchrotron and Super Proton Synchrotron or in proton-proton collisions at √s = 13 TeV, and compared to simulations.