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Long-range correlations between particles separated by a pseudorapidity gap are a powerful tool to explore the initial stages and evolution of the medium created in hadron-hadron collisions. An overview of the long-range correlations measured by the ALICE detector in pp, p-Pb and Pb-Pb will be presented. This includes analyses of forward-backward, two- and multi-particle correlations with the use of the central barrel and forward detectors.

(ProQuest: ... denotes formulae and/or non-USASCII text omitted; see image).We present a measurement of inclusive J/ psi production in p-Pb collisions at ... TeV as a function of the centrality of the collision, as estimated from the energy deposited in the Zero Degree Calorimeters. The measurement is performed with the ALICE detector down to zero transverse momentum, p sub(T), in the backward (-4.46 < y sub(cms) < -2.96) and forward (2.03 < y sub(cms) < 3.53) rapidity intervals in the dimuon decay channel and in the mid-rapidity region (-1.37 < y sub(cms) < 0.43) in the dielectron decay channel. The backward and forward rapidity intervals correspond to the Pb-going and p-going direction, respectively. The p sub(T)-differential J/ psi production cross section at backward and forward rapidity is measured for several centrality classes, together with the corresponding average p sub(T) and p sub(T2) values. The nuclear modification factor is presented as a function of centrality for the three rapidity intervals, and as a function of p sub(T) for several centrality classes at backward and forward rapidity. At mid- and forward rapidity, the J/ psi yield is suppressed up to 40% compared to that in pp interactions scaled by the number of binary collisions. The degree of suppression increases towards central p-Pb collisions at forward rapidity, and with decreasing p sub(T) of the J/ psi . At backward rapidity, the nuclear modification factor is compatible with unity within the total uncertainties, with an increasing trend from peripheral to central p-Pb collisions. [Figure not available: see fulltext.]

We present studies of strange particle yields and correlations in pp collisions in the PYTHIA8 event generator by studying forward-backward correlations. Several key processes that give rise to these correlative effects are identified and manipulated to probe the fundamental properties of strange particle emitting sources. The sensitivity of strange particle production and correlations to PYTHIA's multiparton interaction, color reconnection, and explicit strangeness suppression are shown.

The ALICE Collaboration reports a search for jet quenching effects in high-multiplicity (HM) proton-proton collisions at s = 13 TeV, using the semi-inclusive azimuthal-difference distribution ∆φ of charged-particle jets recoiling from a high transverse momentum (high-pT,trig) trigger hadron. Jet quenching may broaden the ∆φ distribution measured in HM events compared to that in minimum bias (MB) events. The measurement employs a pT,trig-differential observable for data-driven suppression of the contribution of multiple partonic interactions, which is the dominant background. While azimuthal broadening is indeed observed in HM compared to MB events, similar broadening for HM events is observed for simulations based on the PYTHIA 8 Monte Carlo generator, which does not incorporate jet quenching. Detailed analysis of these data and simulations show that the azimuthal broadening is due to bias of the HM selection towards events with multiple jets in the final state. The identification of this bias has implications for all jet quenching searches where selection is made on the event activity. © The Author(s) 2024.

The elliptic flow (v2) of D mesons from beauty-hadron decays (non-prompt D) was measured in midcentral (30–50%) Pb–Pb collisions at a centre-of-mass energy per nucleon pair sNN=5.02 TeV with the ALICE detector at the LHC. The D mesons were reconstructed at midrapidity (| y| < 0.8) from their hadronic decay D → K -π + , in the transverse momentum interval 2 < pT< 12 GeV/c. The result indicates a positive v2 for non-prompt D mesons with a significance of 2.7 σ . The non-prompt D -meson v2 is lower than that of prompt non-strange D mesons with 3.2 σ significance in 2

The production of mesons containing strange quarks ( $\\mbox {$\\mathrm {K0}_{S}}$}$ , phi ) and both singly and doubly strange baryons ( $\\mbox {$\\mathrm {\\Lambda }$}$ , $\\mbox {$\\overline {\\mathrm {\\Lambda }}$}$ , and $\\mbox {$\\mathrm {\\Xi -}+\\overline {\\Xi }+}}$}$ ) are measured at mid-rapidity in pp collisions at $\\sqrt{s}$ = 0.9 ${\\rm TeV}$ with the ALICE experiment at the LHC. The results are obtained from the analysis of about 250 k minimum bias events recorded in 2009. Measurements of yields (dN/dy) and transverse momentum spectra at mid-rapidity for inelastic pp collisions are presented. For mesons, we report yields (dN/dy) of 0.184 plus or minus 0.002(stat.) plus or minus 0.006(sys t.) for $\\mbox {$\\mathrm {K0}_{S}}$}$ and 0.021 plus or minus 0.004(stat.) plus or minus 0.003(sys t.) for phi . For baryons, we find dN/dy=0.048 plus or minus 0.001( stat.) plus or minus 0.004(syst.) for $\\mbox {$\\mathrm {\\Lambda }$}$ , 0.047 plus or minus 0.002(stat.) plus or minus 0.005(sys t.) for $\\mbox {$\\overline {\\mathrm {\\Lambda }}$}$ and 0.0101 plus or minus 0.0020(stat.) plus or minus 0.0009( syst.) for $\\mbox {$\\mathrm {\\Xi -}+\\overline {\\Xi }+}}$}$ . The results are also compared with predictions for identified particle spectra from QCD-inspired models and provide a baseline for comparisons with both future pp measurements at higher energies and heavy-ion collisions.

Measurements of inclusive charged-particle jet production in pp and p-Pb collisions at center-of-mass energy per nucleon-nucleon collision sNN = 5.02 TeV and the corresponding nuclear modification factor RpPbchjet are presented, using data collected with the ALICE detector at the LHC. Jets are reconstructed in the central rapidity region |ηjet| < 0.5 from charged particles using the anti-kT algorithm with resolution parameters R = 0.2, 0.3, and 0.4. The pT-differential inclusive production cross section of charged-particle jets, as well as the corresponding cross section ratios, are reported for pp and p-Pb collisions in the transverse momentum range 10

Abstract The first measurement at midrapidity (|y| < 0.5) of the production yield of the strange-charm baryons $${\\Xi }_{\\text{c}}^{+}$$ and $${\\Xi }_{\\text{c}}^{0}$$ as a function of transverse momentum (p T) in different charged-particle multiplicity classes in proton-proton collisions at $$\\sqrt{s}=13$$ TeV with the ALICE experiment at the LHC is reported. The $${\\Xi }_{\\text{c}}^{+}$$ baryon is reconstructed via the $${\\Xi }_{\\text{c}}^{+}\\to {\\Xi }^{-}{\\pi }^{+}{\\pi }^{+}$$ decay channel in the range 4 < p T < 12 GeV/c, while the $${\\Xi }_{\\text{c}}^{0}$$ baryon is reconstructed via both the $${\\Xi}_{\\text{c}}^{0}\\to {\\Xi}^{-}{\\pi }^{+}$$ and $${\\Xi}_{\\text{c}}^{0}\\to {\\Xi}^{-}{\\text{e}}^{+}{\\nu }_{\\text{e}}$$ decay channels in the range 2 < p T < 12 GeV/c. The baryon-to-meson $$\\left({\\Xi}_{\\text{c}}^{0,+}/{\\text{D}}^{0}\\right)$$ and the baryon-to-baryon $$\\left({\\Xi}_{\\text{c}}^{0,+}/{\\Lambda}_{\\text{c}}^{+}\\right)$$ production yield ratios show no significant dependence on multiplicity. In addition, the observed yield ratios are not described by theoretical predictions that model charm-quark fragmentation based on measurements at e+e − and e − p colliders, indicating differences in the charm-baryon production mechanism in pp collisions. A comparison with different event generators and tunings, including different modelling of the hadronisation process, is also discussed. Moreover, the branching-fraction ratio of $${\\text{BR}}\\left({\\Xi}_{\\text{c}}^{0}\\to {\\Xi }^{-}{\\text{e}}^{+}{\\nu }_{\\text{e}}\\right)/{\\text{BR}}\\left({\\Xi}_{\\text{c}}^{0}\\to {\\Xi }^{-}{\\pi }^{+}\\right)$$ is measured as 0.825 ± 0.094 (stat.) ± 0.081 (syst.). This value supersedes the previous ALICE measurement, improving the statistical precision by a factor of 1.6.

Ultrarelativistic heavy-ion collisions produce a state of hot and dense strongly interacting QCD matter called quark-gluon plasma (QGP). On an event-by-event basis, the volume of the QGP in ultracentral collisions is mostly constant, while its total entropy can vary significantly due to quantum fluctuations, leading to variations in the temperature of the system. Exploiting this unique feature of ultracentral collisions allows for the interpretation of the correlation of the mean transverse momentum$$(\\langle {p}_{\\text{T}}\\rangle )$$of produced charged hadrons and the number of charged hadrons as a measure for the speed of sound, c s . This speed is related to the rate at which compression waves travel in the QGP and is determined by fitting the relative increase in$$\\langle {p}_{\\text{T}}\\rangle $$with respect to the relative change in the average charged-particle density$$(\\langle \\text{d}{N}_{\\text{ch}}/\\text{d}\\eta \\rangle )$$measured at mid-rapidity. This study reports the event-average$$\\langle {p}_{\\text{T}}\\rangle $$of charged particles as well as the variance, skewness, and kurtosis of the event-by-event transverse momentum per charged particle$$([{p}_{\\text{T}}])$$distribution in ultracentral Pb-Pb collisions at a center-of-mass energy of 5 . 02 TeV per nucleon pair using the ALICE detector. Different centrality estimators based on charged-particle multiplicity or the transverse energy of the event are used to select ultracentral collisions. By ensuring a pseudorapidity gap between the region used to define the centrality and the region used to perform the measurement, the influence of biases and their potential effects on the rise of the mean transverse momentum is tested. The measured$${c}_{\\text{s}}^{2}$$is found to strongly depend on the exploited centrality estimator and ranges between 0 . 1146±0 . 0028 (stat . )±0 . 0065 (syst . ) and 0 . 4374±0 . 0006 (stat . )±0 . 0184 (syst . ) in natural units. The self-normalized variance shows a steep decrease towards ultracentral collisions, while the self-normalized skewness variables show a maximum, followed by a fast decrease. These non-Gaussian features are understood in terms of the vanishing of the impact-parameter fluctuations contributing to the event-to-event [ p T ] distribution.

The first measurement of prompt D *+ -meson spin alignment in ultrarelativistic heavy-ion collisions with respect to the direction orthogonal to the reaction plane is presented. The spin alignment is quantified by measuring the element ρ 00 of the diagonal spin-density matrix for prompt D *+ mesons with 4 < p T < 30 GeV /c in two rapidity intervals, | y | < 0 . 3 and 0 . 3 < | y | < 0 . 8, in central (0–10%) and midcentral (30–50%) Pb–Pb collisions at$$\\sqrt{{s}_{\\text{NN}}}={5}.0{2}$$TeV. Evidence of spin alignment ρ 00 > 1 / 3 has been found for p T > 15 GeV /c and 0 . 3 < | y | < 0 . 8 with a significance of 3 . 1 σ . The measured spin alignment of prompt D *+ mesons is compared with the one of inclusive J / ψ mesons measured at forward rapidity (2 . 5 < y < 4).