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Item type:Publication, Measurement of the production and elliptic flow of (anti)nuclei in Xe–Xe collisions at √sNN = 5.44 TeV(American Physical Society, 2024-12-01)Measurements of (anti)deuteron and (anti)He3 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 sNN=5.44 TeV are presented. The coalescence parameters B2 and B3 are measured as a function of the transverse momentum per nucleon. The ratios between (anti)deuteron and (anti)He3 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 grand-canonical-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 Tchem=(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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Measurement of the impact-parameter-dependent azimuthal anisotropy in coherent ρ0 photoproduction in Pb–Pb collisions at √sNN = 5.02 TeV(Elsevier B.V., 2024-11-01)This Letter presents the first measurement of the impact-parameter dependent angular anisotropy in the decay of coherently photoproduced ρ0 mesons. The ρ0 mesons are reconstructed through their decay into pion pairs. The measured anisotropy corresponds to the amplitude of the cos(2ϕ) modulation, where ϕ 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 sNN=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(2ϕ) modulation is found to increase by about one order of magnitude from large to small impact parameters. Theoretical calculations describe the measured cos(2ϕ) 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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Investigating the composition of the K0⁎(700) state with π±KS0 correlations at the LHC(Elsevier B.V., 2024-09-01)The first measurements of femtoscopic correlations with the particle pair combinations π±KS0 in pp collisions at s=13 TeV at the Large Hadron Collider (LHC) are reported by the ALICE experiment. Using the femtoscopic approach, it is shown that it is possible to study the elusive K0⁎(700) particle that has been considered a tetraquark candidate for over forty years. Source and final-state interaction parameters are extracted by fitting a model assuming a Gaussian source to the experimentally measured two-particle correlation functions. The final-state interaction in the π±KS0 system is modeled through a resonant scattering amplitude, defined in terms of a mass and a coupling parameter, The extracted mass and Breit–Wigner width, derived from the coupling parameter, of the final-state interaction are found to be consistent with previous measurements of the K0⁎(700). The small value and increase of the correlation strength with increasing source size support the hypothesis that the K0⁎(700) is a four-quark state, i.e. a tetraquark state of the form (q1,q2‾,q3,q3‾) in which q1, q2 and q3 indicate the flavor of the valence quarks of the π and KS0. This latter trend is also confirmed via a simple geometric model that assumes a tetraquark structure of the K0⁎(700) resonance. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Systematic study of flow vector fluctuations in √sNN = 5.02 TeV Pb–Pb collisions(American Physical Society, 2024-06-01)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, Phys. Rev. C 107, L051901 (2023)2469-998510.1103/PhysRevC.107.L051901] 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 V - 2 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 V - 3 or V - 4 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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Measurement of ωc0 baryon production and branching-fraction ratio BR(ωc0 → ω−e+νe)/BR(ωc0 → ω−π+) in pp collisions at √s = 13 TeV(American Physical Society, 2024-08-01)The inclusive production of the charm-strange baryon ωc0 is measured for the first time via its semileptonic decay into ω-e+νe at midrapidity (|y|<0.8) in proton-proton (pp) collisions at the center-of-mass energy 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<pT<12 GeV/c. The branching-fraction ratio BR(ωc0→ω-e+νe)/BR(ωc0→ω-π+) 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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Studying the interaction between charm and light-flavor mesons(American Physical Society, 2024-08-01)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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Measurements of chemical potentials in Pb–Pb collisions at √sNN = 5.02 TeV(American Physical Society, 2024-08-30)This Letter presents the most precise measurement to date of the matter-antimatter imbalance at midrapidity in Pb-Pb collisions at a center-of-mass energy per nucleon pair sNN=5.02 TeV. Using the Statistical Hadronization framework, it is possible to obtain the value of the electric charge and baryon chemical potentials, μQ=-0.18±0.90 MeV and μB=0.71±0.45 MeV, with unprecedented precision. A centrality-differential study of the antiparticle-to-particle yield ratios of charged pions, protons, ω baryons, and light (hyper)nuclei is performed. These results indicate that the system created in Pb-Pb collisions at the LHC is on average baryon-free and electrically neutral at midrapidity.2 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Investigating strangeness enhancement in jet and medium via 𝜙(1020) production in p–Pb collisions at √sNN = 5.02 TeV(American Physical Society, 2024-12-01)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 ((Formula presented)) acting as a jet proxy and a produced strange hadron [(Formula presented) meson]. Measuring (Formula presented) correlations at midrapidity in (Formula presented)-Pb collisions at (Formula presented) 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 (Formula presented) 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 (Formula presented) and dihadron correlations show that the observed strangeness enhancement is largely driven by the underlying event, where the (Formula presented) ratio is significantly larger than within the jet regions. As multiplicity increases, the fraction of the total (Formula presented) 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. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Measurement of beauty-quark production in pp collisions at √s = 13 TeV via non-prompt D mesons(Springer Science and Business Media Deutschland GmbH, 2024-10-01)The pT-differential production cross sections of non-prompt D0, D+, and Ds+ 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+, Ds+, and Λc+ hadron measurements, obtaining dσ/dy=75.2±3.2stat.±5.2syst.−3.2+12.3extrap. μb. - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Measurement of beauty production via non-prompt charm hadrons in p–Pb collisions at √sNN = 5.02 TeV(Springer Science and Business Media Deutschland GmbH, 2024-11-01)The production cross sections of D0, D+, and Λc+ hadrons originating from beauty-hadron decays (i.e. non-prompt) were measured for the first time at midrapidity in proton–lead (p–Pb) collisions at the center-of-mass energy per nucleon pair of sNN = 5.02 TeV. Nuclear modification factors (RpPb) of non-prompt D0, D+, and Λc+ are calculated as a function of the transverse momentum (pT) to investigate the modification of the momentum spectra measured in p–Pb collisions with respect to those measured in proton–proton (pp) collisions at the same energy. The RpPb measurements are compatible with unity and with the measurements in the prompt charm sector, and do not show a significant pT dependence. The pT-integrated cross sections and pT-integrated RpPb of non-prompt D0 and D+ mesons are also computed by extrapolating the visible cross sections down to pT = 0. The non-prompt D-meson RpPb integrated over pT is compatible with unity and with model calculations implementing modification of the parton distribution functions of nucleons bound in nuclei with respect to free nucleons. The non-prompt Λc+/D0 and D+/D0 production ratios are computed to investigate hadronisation mechanisms of beauty quarks into mesons and baryons. The measured ratios as a function of pT display a similar trend to that measured for charm hadrons in the same collision system.