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Search for quasi-particle scattering in the quark-gluon plasma with jet splittings in pp and PbPb collisions at = 5.02 TeV
No full textThe ALICE Collaboration reports measurements of the large relative transverse momentum () component of jet substructure in pp and in central and semicentral PbPb collisions at center-of-mass energy per nucleon pair TeV. Enhancement in the yield of such large- emissions in central PbPb collisions is predicted to arise from partonic scattering with quasi-particles of the quark--gluon plasma. The analysis utilizes charged-particle jets reconstructed by the anti- algorithm with resolution parameter in the transverse-momentum interval $6
System size and energy dependence of the mean transverse momentum fluctuations at the LHC
No full textEvent-by-event fluctuations of the event-wise mean transverse momentum, , of charged particles produced in proton–proton (pp) collisions at = 5.02 TeV, Xe–Xe collisions at = 5.44 TeV, and Pb–Pb collisions at = 5.02 TeV are studied using the ALICE detector based on the integral correlator . The correlator strength is found to decrease monotonically with increasing produced charged-particle multiplicity measured at midrapidity in all three systems. In Xe–Xe and Pb–Pb collisions, the multiplicity dependence of the correlator deviates significantly from a simple power-law scaling as well as from the predictions of the HIJING and AMPT models. The observed deviation from power-law scaling is expected from transverse radial flow in semicentral to central Xe–Xe and Pb–Pb collisions. In pp collisions, the correlation strength is also studied by classifying the events based on the transverse spherocity, , of the particle production at midrapidity, used as a proxy for the presence of a pronounced back-to-back jet topology. Low-spherocity (jetty) events feature a larger correlation strength than those with high spherocity (isotropic). The strength and multiplicity dependence of jetty and isotropic events are well reproduced by calculations with the PYTHIA 8 and EPOS LHC models
-meson-tagged jet axes difference in proton-proton collisions at = 5.02 TeV
No full textHeavy-flavor quarks produced in proton-proton (pp) collisions provide a unique opportunity to investigate the evolution of quark-initiated parton showers from initial hard scatterings to final-state hadrons. By examining jets that contain heavy-flavor hadrons, this study explores the effects of both perturbative and nonperturbative QCD on jet formation and structure. The angular differences between various jet axes, ΔR, offer insight into the radiation patterns and fragmentation of charm quarks. The first measurement of D-tagged jet axes differences in pp collisions at = 5.02 TeV by the ALICE experiment at the LHC is presented for jets with transverse momentum ≥ 10 GeV/ c and D mesons with ≥ 5 GeV/ c. In this D-meson-tagged jet measurement, three jet axis definitions, each with different sensitivities to soft, wide-angle radiation, are used: the standard axis, soft drop groomed axis, and winner-takes-all axis. Measurements of the radial distributions of D mesons with respect to the jet axes, , are reported, along with the angle, , between the three jet axes. The D meson emerges as the leading particle in these jets, closely aligning with the winner-takes-all axis and diverging from the standard jet axis. The results also examine how varying the sensitivity to soft radiation with grooming influences the orientation of the soft drop jet axis and uncover that charm-jet structure is more likely to survive grooming when the soft drop axis is further from the D direction, providing further evidence of the dead-cone effect recently measured by ALICE
Measurement of correlations among net-charge, net-proton, and net-kaon multiplicity distributions in Pb-Pb collisions at = 5.02 TeV
No full textCorrelations among conserved quantum numbers, such as the net-electric charge, the net-baryon, and the net-strangeness in heavy-ion collisions, are crucial for exploring the QCD phase diagram. In this paper, these correlations are investigated using net-proton number (as a proxy for the net-baryon), net-kaon number (for the net-strangeness), and net-charged particle number in Pb-Pb collisions at = 5.02 TeV with the ALICE detector. The observed correlations deviate from the Poissonian baseline, with a more pronounced deviation at LHC energies than at RHIC. Theoretical calculations of the Thermal-FIST hadron resonance gas model, HIJING, and EPOS LHC event generators are compared with experimental results, where a significant impact of resonance decays is observed. Thermal-FIST calculations under the grand canonical and canonical ensembles highlight significant differences, underscoring the role of local charge conservation in explaining the data. Recent lattice QCD studies have demonstrated that the magnetic field generated by spectator protons in heavy-ion collisions affects susceptibility ratios, in particular those related to the net-electric charge and the net-baryon numbers. The experimental findings are in qualitative agreement with the expectations of lattice QCD.[graphic not available: see fulltext
Measurement of correlations among net-charge, net-proton, and net-kaon multiplicity distributions in Pb-Pb collisions at TeV
No full textMeasurements of fluctuations and correlations of net-charge, net-pion, net-kaon, and net-proton in PbPb collisions at = 5.02 TeV using the ALICE detector at the CERN LHC. The diagonal and off-diagonal cumulants of net-charge, net-pion, net-kaon, and net-proton and also their ratios are presented as a function of centrality
