This Letter presents the first measurement of event-by-event fluctuations of the net number (difference between the particle and antiparticle multiplicities) of multistrange hadrons Ξ^{-} and Ξ[over ¯]^{+} and its correlation with the net-kaon number using the data collected by the ALICE Collaboration in pp, p-Pb, and Pb-Pb collisions at a center-of-mass energy per nucleon pair sqrt[s_{NN}]=5.02  TeV. The statistical hadronization model with a correlation over three units of rapidity between hadrons having the same and opposite strangeness content successfully describes the results. On the other hand, string-fragmentation models that mainly correlate strange hadrons with opposite strange quark content over a small rapidity range fail to describe the data.

The pT-differential cross section of ω meson production in pp collisions at √(s) = 13 TeV at midrapidity (|y| < 0.5) was measured with the ALICE detector at the LHC, covering an unprecedented transverse-momentum range of 1.6 < pT < 50 GeV/c. The meson is reconstructed via the ω → π+π−π0 decay channel. The results are compared with various theoretical calculations: PYTHIA8.2 with the Monash 2013 tune overestimates the data by up to 50

The production yields of antideuterons and antiprotons are measured in pp collisions at a center-of-mass energy of root s = 13 TeV, as a function of transverse momentum (p(T)) and rapidity (y), for the first time rapidity-differentially up to vertical bar y vertical bar = 0.7. The measured spectra are used to study the p(T) and rapidity dependence of the coalescence parameter B-2, which quantifies the coalescence probability of antideuterons. The p(T) and rapidity dependence of the obtained B-2 is extrapolated for p(T) > 1.7 GeV/c and vertical bar y vertical bar > 0.7 using the phenomenological antideuteron production model implemented in PYTHIA 8.3 as well as a baryon coalescence afterburner model based on EPOS 3. Such measurements are of interest to the astrophysics community, since they can be used for the calculation of the flux of antinuclei from cosmic rays, in combination with coalescence models.

The first measurement of HΛ3 and H‾Λ‾3 differential production with respect to transverse momentum and centrality in Pb–Pb collisions at sNN=5.02 TeV is presented. The HΛ3 has been reconstructed via its two-charged-body decay channel, i.e., HΛ3→3He+π−. A Blast-Wave model fit of the pT-differential spectra of all nuclear species measured by the ALICE collaboration suggests that the HΛ3 kinetic freeze-out surface is consistent with that of other nuclei. The ratio between the integrated yields of HΛ3 and He3 is compared to predictions from the statistical hadronisation model and the coalescence model, with the latter being favoured by the presented measurements.

The two-particle momentum correlation functions between charm mesons (D*± and D±) and charged light-flavor mesons (π± and K±) in all charge combinations are measured for the first time by the ALICE Collaboration in high-multiplicity proton–proton collisions at a center-of-mass energy of s=13 TeV. For DK and D*K pairs, the experimental results are in agreement with theoretical predictions of the residual strong interaction based on quantum chromodynamics calculations on the lattice and chiral effective field theory. In the case of Dπ and D*π pairs, tension between the calculations including strong interactions and the measurement is observed. For all particle pairs, the data can be adequately described by Coulomb interaction only, indicating a shallow interaction between charm and light-flavor mesons. Finally, the scattering lengths governing the residual strong interaction of the Dπ and D*π systems are determined by fitting the experimental correlation functions with a model that employs a Gaussian potential. The extracted values are small and compatible with zero. © 2024 CERN, for the ALICE Collaboration 2024 CERN

Abstract The total charm-quark production cross section per unit of rapidity $$\textrm{d}\sigma ({{\textrm{c}}\overline{\textrm{c}}})/\textrm{d}y$$ d σ ( c c ¯ ) / d y , and the fragmentation fractions of charm quarks to different charm-hadron species $$f(\textrm{c}\rightarrow {\textrm{h}}_{\textrm{c}})$$ f ( c → h c ) , are measured for the first time in p–Pb collisions at $$\sqrt{s_\textrm{NN}} = 5.02~\text {Te}\hspace{-1.00006pt}\textrm{V} $$ s NN = 5.02 Te V at midrapidity ( $$-0.96 - 0.96 < y < 0.04 in the centre-of-mass frame) using data collected by ALICE at the CERN LHC. The results are obtained based on all the available measurements of prompt production of ground-state charm-hadron species: $$\textrm{D}^{0}$$ D 0 , $$\textrm{D}^{+}$$ D + , $$\textrm{D}_\textrm{s}^{+}$$ D s + , and $$\mathrm {J/\psi }$$ J / ψ mesons, and $$\Lambda _\textrm{c}^{+}$$ Λ c + and $$\Xi _\textrm{c}^{0}$$ Ξ c 0 baryons. The resulting cross section is $$ \textrm{d}\sigma ({{\textrm{c}}\overline{\textrm{c}}})/\textrm{d}y =219.6 \pm 6.3\;(\mathrm {stat.}) {\;}_{-11.8}^{+10.5}\;(\mathrm {syst.}) {\;}_{-2.9}^{+8.3}\;(\mathrm {extr.})\pm 5.4\;(\textrm{BR})\pm 4.6\;(\mathrm {lumi.}) \pm 19.5\;(\text {rapidity shape})+15.0\;(\Omega _\textrm{c}^{0})\;\textrm{mb} $$ d σ ( c c ¯ ) / d y = 219.6 ± 6.3 ( stat . ) - 11.8 + 10.5 ( syst . ) - 2.9 + 8.3 ( extr . ) ± 5.4 ( BR ) ± 4.6 ( lumi . ) ± 19.5 ( rapidity shape ) + 15.0 ( Ω c 0 ) mb , which is consistent with a binary scaling of pQCD calculations from pp collisions. The measured fragmentation fractions are compatible with those measured in pp collisions at $$\sqrt{s} = 5.02$$ s = 5.02 and 13 TeV, showing an increase in the relative production rates of charm baryons with respect to charm mesons in pp and p–Pb collisions compared with $$\mathrm {e^{+}e^{-}}$$ e + e - and $$\mathrm {e^{-}p}$$ e - p collisions. The $$p_\textrm{T}$$ p T -integrated nuclear modification factor of charm quarks, $$R_\textrm{pPb}({\textrm{c}}\overline{\textrm{c}})= 0.91 \pm 0.04\;\mathrm{(stat.)} ^{+0.08}_{-0.09}\;\mathrm{(syst.)} ^{+0.05}_{-0.03}\;\mathrm{(extr.)} \pm 0.03\;\mathrm{(lumi.)}$$ R pPb ( c c ¯ ) = 0.91 ± 0.04 ( stat . ) - 0.09 + 0.08 ( syst . ) - 0.03 + 0.05 ( extr . ) ± 0.03 ( lumi . ) , is found to be consistent with unity and with theoretical predictions including nuclear modifications of the parton distribution functions.

The inclusive production of the charm-strange baryon Omega(0)(c) is measured for the first time via its semileptonic decay into Omega(-)e(+)nu(e) at midrapidity (vertical bar y vertical bar < 0.8) in proton-proton (pp) collisions at the center-of-mass energy root s =13 TeV with the ALICE detector at the LHC. The transverse momentum (pT) differential cross section multiplied by the branching ratio is presented in the interval 2 < p(T) < 12 GeV=c. The branching-fraction ratio BR(Omega(0)(c) -> Omega(-)e(+)nu(e))/BR(Omega(0)(c) -> Omega(-)pi(+)) is measured to be 1.12 +/- 0.22 (stat) +/- 0.27 (syst). Comparisons with other experimental measurements, as well as with theoretical calculations, are presented.

Measurements of the pT-dependent flow vector fluctuations in Pb–Pb collisions at sNN=5.02TeV using azimuthal correlations with the ALICE experiment at the Large Hadron Collider are presented. A four-particle correlation approach [ALICE Collaboration, ] is used to quantify the effects of flow angle and magnitude fluctuations separately. This paper extends previous studies to additional centrality intervals and provides measurements of the pT-dependent flow vector fluctuations at sNN=5.02TeV with two-particle correlations. Significant pT-dependent fluctuations of the V⃗2 flow vector in Pb–Pb collisions are found across different centrality ranges, with the largest fluctuations of up to ∼15% being present in the 5% most central collisions. In parallel, no evidence of significant pT-dependent fluctuations of V⃗3 or V⃗4 is found. Additionally, evidence of flow angle and magnitude fluctuations is observed with more than 5σ significance in central collisions. These observations in Pb–Pb collisions indicate where the classical picture of hydrodynamic modeling with a common symmetry plane breaks down. This has implications for hard probes at high pT, which might be biased by pT-dependent flow angle fluctuations of at least 23% in central collisions. Given the presented results, existing theoretical models should be reexamined to improve our understanding of initial conditions, quark–gluon plasma properties, and the dynamic evolution of the created system. ©2024 CERN, for the ALICE Collaboration 2024 CERN

This Letter presents the first measurement of the impact-parameter dependent angular anisotropy in the decay of coherently photoproduced rho(0) mesons. The rho(0) mesons are reconstructed through their decay into pion pairs. The measured anisotropy corresponds to the amplitude of the cos(2 phi) modulation, where phi is the angle between the two vectors formed by the sum and the difference of the transverse momenta of the pions, respectively. The measurement was performed by the ALICE Collaboration at the LHC using data from ultraperipheral Pb-Pb collisions at a center-of-mass energy of root s(NN) = 5.02 TeV per nucleon pair. Different impact-parameter regions are selected by classifying the events in nuclear-breakup classes. The amplitude of the cos(2 phi) modulation is found to increase by about one order of magnitude from large to small impact parameters. Theoretical calculations describe the measured cos(2 phi) anisotropy and its impact-parameter dependence as the result of a quantum interference effect at the femtometer scale, arising from the ambiguity regarding which of the nuclei is the photon source in the interaction.

A study of strange hadron production associated with hard scattering processes and with the underlying event is conducted to investigate the origin of the enhanced production of strange hadrons in small collision systems characterised by large charged-particle multiplicities. For this purpose, the production of the single-strange meson K_S^0 and the double-strange baryon Ξ± is measured, in each event, in the azimuthal direction of the highest-pT particle (“trigger” particle), related to hard scattering processes, and in the direction transverse to it in azimuth, associated with the underlying event, in pp collisions at √(s) = 5.02 TeV and √(s) = 13 TeV using the ALICE detector at the LHC. The per-trigger yields of K_S^0 and Ξ± are dominated by the transverse-to-leading production (i.e., in the direction transverse to the trigger particle), whose contribution relative to the toward-leading production is observed to increase with the event charged-particle multiplicity. The transverse-to-leading and the toward-leading Ξ±/ K_S^0 yield ratios increase with the multiplicity of charged particles, suggesting that strangeness enhancement with multiplicity is associated with both hard scattering processes and the underlying event. The relative production of Ξ± with respect to K_S^0 is higher in transverse-to-leading processes over the whole multiplicity interval covered by the measurement. The K_S^0 and Ξ± per-trigger yields and yield ratios are compared with predictions of three different phenomenological models, namely Pythia8.2 with the Monash tune, Pythia8.2 with ropes and EPOS LHC. The comparison shows that none of them can quantitatively describe either the transverse-to-leading or the toward-leading yields of K_S^0 and Ξ±.

The pT-differential production cross sections of non-prompt D0, D+, and D_s^+ mesons originating from beauty-hadron decays are measured in proton–proton collisions at a centre-of-mass energy √(s) = 13 TeV. The measurements are performed at midrapidity, |y| < 0.5, with the data sample collected by ALICE from 2016 to 2018. The results are in agreement with predictions from several perturbative QCD calculations. The fragmentation fraction of beauty quarks to strange mesons divided by the one to non-strange mesons, fs/(fu + fd), is found to be 0.114 ± 0.016 (stat.) ± 0.006 (syst.) ± 0.003 (BR) ± 0.003 (extrap.). This value is compatible with previous measurements at lower centre-of-mass energies and in different collision systems in agreement with the assumption of universality of fragmentation functions. In addition, the dependence of the non-prompt D meson production on the centre-of-mass energy is investigated by comparing the results obtained at √(s) = 5.02 and 13 TeV, showing a hardening of the non-prompt D-meson pT-differential production cross section at higher √(s) . Finally, the bb production cross section per unit of rapidity at midrapidity is calculated from the non-prompt D0, D+, D_s^+ , and Λ_c^+ hadron measurements, obtaining dσ /dy=75.2± 3.2(stat.)± 5.2(syst.)_-3.2^+12.3(extrap.) μb.

This work aims to differentiate strangeness produced from hard processes (jetlike) and softer processes (underlying event) by measuring the angular correlation between a high-momentum trigger hadron (h) acting as a jet proxy and a produced strange hadron [f(1020) meson]. Measuring h-phi correlations at midrapidity in p-Pb collisions at root s(NN) = 5.02 TeV as a function of event multiplicity provides insight into the microscopic origin of strangeness enhancement in small collision systems. The jetlike and the underlying-event-like strangeness production are investigated as a function of event multiplicity. They are also compared between a lower and higher momentum region. The evolutions of the per-trigger yields within the near-side (aligned with the trigger hadron) and away-side (in the opposite direction of the trigger hadron) jets are studied separately, allowing for the characterization of two distinct jetlike production regimes. Furthermore, the h-phi correlations within the underlying event give access to a production regime dominated by soft production processes, which can be compared directly to the in-jet production. Comparisons between h-phi and dihadron correlations show that the observed strangeness enhancement is largely driven by the underlying event, where the phi/h ratio is significantly larger than within the jet regions. As multiplicity increases, the fraction of the total phi(1020) yield coming from jets decreases compared to the underlying event production, leading to high-multiplicity events being dominated by the increased strangeness production from the underlying event.

Measurements of (anti)deuteron and (anti)He-3 production in the rapidity range |y| < 0.5 as a function of the transverse momentum and event multiplicity in Xe-Xe collisions at a center-of-mass energy per nucleon-nucleon pair of root s(NN) = 5.44 TeV are presented. The coalescence parameters B-2 and B-3 are measured as a function of the transverse momentum per nucleon. The ratios between (anti)deuteron and (anti)He-3 yields and those of (anti)protons and pions are reported as a function of the mean charged-particle multiplicity density and compared with two implementations of the statistical hadronization model and with coalescence predictions. The elliptic flow of (anti)deuterons is measured for the first time in Xe-Xe collisions and shows features similar to those already observed in Pb-Pb collisions, i.e., the mass ordering at low transverse momentum and the meson-baryon grouping at intermediate transverse momentum. The production of nuclei is particularly sensitive to the chemical freeze-out temperature of the system created in the collision, which is extracted from a grandcanonical-ensemble-based thermal fit, performed for the first time including light nuclei along with light-flavor hadrons in Xe-Xe collisions. The extracted chemical freeze-out temperature T-chem = (154.2 +/- 1.1) MeV in Xe-Xe collisions is similar to that observed in Pb-Pb collisions and close to the crossover temperature predicted by lattice quantum chromodynamics calculations.

PANDA (anti-Proton ANnihiliation at DArmstadt) is planned to be one of the four main experiments at the future international accelerator complex FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. It is going to address fundamental questions of hadron physics and quantum chromodynamics using cooled antiproton beams with a high intensity and and momenta between 1.5 and 15 GeV/c. PANDA is designed to reach a maximum luminosity of 2x10^32 cm^2 s. Most of the physics programs require an excellent particle identification (PID). The PID of hadronic states at the forward endcap of the target spectrometer will be done by a fast and compact Cherenkov detector that uses the detection of internally reflected Cherenkov light (DIRC) principle. It is designed to cover the polar angle range from 5{\deg} to 22{\deg} and to provide a separation power for the separation of charged pions and kaons up to 3 standard deviations (s.d.) for particle momenta up to 4 GeV/c in order to cover the important particle phase space. This document describes the technical design and the expected performance of the novel PANDA Disc DIRC detector that has not been used in any other high energy physics experiment (HEP) before. The performance has been studied with Monte-Carlo simulations and various beam tests at DESY and CERN. The final design meets all PANDA requirements and guarantees suffcient safety margins.

This documents describes the technical design and the expected performance of the Barrel DIRC detector for the PANDA experiment. The Barrel DIRC will provide hadronic charged particle identification in the polar angle range of $22^\circ$ to $140^\circ$ for particle momenta between 0.5 GeV/c and 3.5 GeV/c. The design is based on the successful BaBar DIRC with several key improvements. The performance and system cost were optimized in detailed detector simulations and validated with full system prototypes using particle beams at GSI and CERN. The final design meets or exceeds the PID goal of clean $π/K$ separation with at least 3 standard deviations over the entire phase space of charged kaons in the Barrel DIRC.

The (P) over bar ANDA (anti-Proton ANnihiliation at DArmstadt) experiment will be one of the four flagship experiments at the new international accelerator complex FAIR (Facility for Antiproton and Ion Research) in Darmstadt, Germany. (P) over bar ANDA will address fundamental questions of hadron physics and quantum chromodynamics using high-intensity cooled antiproton beams with momenta between 1.5 and 15 GeV/c and a design luminosity of up to 2 x 10(32) cm(-2) S-1. Excellent particle identification (PID) is crucial to the success of the (P) over bar ANDA physics program. Hadronic PID in the barrel region of the target spectrometer will be performed by a fast and compact Cherenkov counter using the detection of internally reflected Cherenkov light (DIRC) technology. It is designed to cover the polar angle range from 22 degrees to 140 degrees and will provide at least 3 standard deviations (s.d.) pi/K separation up to 3.5 GeV/c, matching the expected upper limit of the final state kaon momentum distribution from simulation. This documents describes the technical design and the expected performance of the (P) over bar ANDA Barrel DIRC detector. The design is based on the successful BaBar DIRC with several key improvements. The performance and system cost were optimized in detailed detector simulations and validated with full system prototypes using particle beams at GSI and CERN. The final design meets or exceeds the PID goal of clean pi/K separation with at least 3 s.d. over the entire phase space of charged kaons in the Barrel DIRC.

Substantial experimental and theoretical efforts worldwide are devoted to explore the phase diagram of strongly interacting matter. At LHC and top RHIC energies, QCD matter is studied at very high temperatures and nearly vanishing net-baryon densities. There is evidence that a Quark-Gluon-Plasma (QGP) was created at experiments at RHIC and LHC. The transition from the QGP back to the hadron gas is found to be a smooth cross over. For larger net-baryon densities and lower temperatures, it is expected that the QCD phase diagram exhibits a rich structure, such as a first-order phase transition between hadronic and partonic matter which terminates in a critical point, or exotic phases like quarkyonic matter. The discovery of these landmarks would be a breakthrough in our understanding of the strong interaction and is therefore in the focus of various high-energy heavy-ion research programs. The Compressed Baryonic Matter (CBM) experiment at FAIR will play a unique role in the exploration of the QCD phase diagram in the region of high net-baryon densities, because it is designed to run at unprecedented interaction rates. High-rate operation is the key prerequisite for high-precision measurements of multi-differential observables and of rare diagnostic probes which are sensitive to the dense phase of the nuclear fireball. The goal of the CBM experiment at SIS100 (sqrt(s_NN) = 2.7 - 4.9 GeV) is to discover fundamental properties of QCD matter: the phase structure at large baryon-chemical potentials (mu_B > 500 MeV), effects of chiral symmetry, and the equation-of-state at high density as it is expected to occur in the core of neutron stars. In this article, we review the motivation for and the physics programme of CBM, including activities before the start of data taking in 2022, in the context of the worldwide efforts to explore high-density QCD matter.

The exclusive charmonium production process in $\overline{p}p$ annihilation with an associated ${\ensuremath{\pi}}^{0}$ meson $\overline{p}p\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{0}$ is studied in the framework of QCD collinear factorization. The feasibility of measuring this reaction through the $J/\ensuremath{\psi}\ensuremath{\rightarrow}{e}^{+}{e}^{\ensuremath{-}}$ decay channel with the AntiProton ANnihilation at DArmstadt ($\overline{\mathsf{P}}\mathsf{ANDA}$) experiment is investigated. Simulations on signal reconstruction efficiency as well as the background rejection from various sources including the $\overline{p}p\ensuremath{\rightarrow}{\ensuremath{\pi}}^{+}{\ensuremath{\pi}}^{\ensuremath{-}}{\ensuremath{\pi}}^{0}$ and $\overline{p}p\ensuremath{\rightarrow}J/\ensuremath{\psi}{\ensuremath{\pi}}^{0}{\ensuremath{\pi}}^{0}$ reactions are performed with PandaRoot, the simulation and analysis software framework of the $\overline{\mathsf{P}}\mathsf{ANDA}$ experiment. It is shown that the measurement can be done at $\overline{\mathsf{P}}\mathsf{ANDA}$ with significant constraining power under the assumption of an integrated luminosity attainable in four to five months of data taking at the maximum design luminosity.

Bound nuclear systems with two units of strangeness are still poorly known despite their importance for many strong interaction phenomena. Stored antiprotons beams in the GeV range represent an unparalleled factory for various hyperon-antihyperon pairs. Their outstanding large production probability in antiproton collisions will open the floodgates for a series of new studies of systems which contain two or even more units of strangeness at the PANDA experiment at FAIR. For the first time, high resolution gamma-spectroscopy of doubly strange Lambda Lambda-hypernuclei will be performed, thus complementing measurements of ground state decays of Lambda Lambda-hypernuclei at J-PARC or possible decays of particle unstable hypernuclei in heavy ion reactions. High resolution spectroscopy of multistrange Xi(-) -atoms will be feasible and even the production of Omega(-) -atoms will be within reach. The latter might open the door to the vertical bar S vertical bar = 3 world in strangeness nuclear physics, by the study of the hadronic Omega(-) -nucleus interaction. For the first time it will be possible to study the behavior of Xi(+) in nuclear systems under well controlled conditions. (C) 2016 Elsevier B.V. All rights reserved.

The results of simulations for future measurements of electromagnetic form factors at \PANDA (FAIR) within the PandaRoot software framework are reported. The statistical precision at which the proton form factors can be determined is estimated. The signal channel $\bar p p \to e^+ e^-$ is studied on the basis of two different but consistent procedures. The suppression of the main background channel, i.e. the $\bar p p \to \pi^+ \pi^-$, is studied. Furthermore, the background versus signal efficiency, statistic and systematic uncertainties on the extracted proton form factors are evaluated using to the two different procedures. The results are consistent with those of a previous simulation study using an older, simplified framework. However, a slightly better precision is achieved in the PandaRoot study in a large range of momentum transfer, assuming the nominal beam condition and detector performances.