Phase Equilibrium and Synthesis in Ionic Melts of the System Na2WO4-K2WO4-Pb2WO4

Interest in a comprehensive study of lead tungstate single crystals is due to its scintillation properties [1-5]. It was found that lead tungstate occupies an exceptional position in the family of tungstates with a scheelite structure. Lead tungstate single crystal is a scintillation material [1] used in the LHC electromagnetic calorimeter and photon detector in the ALICE experiment at CERN [1, 2]. Now it can be said unequivocally that lead tungstate is the most promising scintillation material in the next decade.

Sudden increase in the degrees of freedom in dense QCD matter

In this paper, we analyzed charged particle transverse momentum spectra in high multiplicity events in proton–proton and nucleus–nucleus collisions at LHC energies from the ALICE experiment using the color string percolation model (CSPM). The color reduction factor and associated string density parameters are extracted for various multiplicity classes in [Formula: see text] collisions and centrality classes for heavy-ion collisions at various LHC energies to study the effect of collision geometry and collision energy. These parameters are used to extract the thermodynamical quantities temperature and the energy density of the hot nuclear matter. A universal scaling is observed in initial temperature when studied as a function of charged particle multiplicity scaled by transverse overlap area. From the measured initial energy density [Formula: see text] and the initial temperature T, a dimensionless quantity [Formula: see text] is constructed which is used to obtain the degrees of freedom (DOF) of the deconfined phase. A two-step behavior and a sudden increase in DOF of [Formula: see text]47 for the ideal gas, above the hadronization temperature (T [Formula: see text] 210[Formula: see text]MeV), are observed in case of heavy-ion collisions at LHC energies.

Azimuthal Correlations of D Mesons with Charged Particles in Simulations with the ALICE Experiment

In this work, we present the results of a component-level analysis with Monte Carlo simulations, which aid the interpretation of recent ALICE results of the azimutal correlation distribution of prompt D mesons with charged hadrons in pp and p–Pb collisions at sNN = 5.02 TeV. Parton-level contributions and fragmentation properties are evaluated. Charm and beauty contributions are compared in order to identify the observables that serve as sensitive probes of the production and hadronisation of heavy quarks.

Event-by-Event Particle Ratio Fluctuations at LHC Energies

A Monte Carlo study of identified particle ratio fluctuations at LHC energies is carried out in the framework of HIJING model using the fluctuation variable ν dyn . The simulated events for Pb-Pb collisions at s N N = 2.76 and 5.02 TeV and Xe-Xe collisions at s N N = 5.44 TeV are analyzed. From this study, it is observed that the values of π , K , p , K , and π , p follow the similar trends of energy dependence as observed in the most central collision data by NA49, STAR, and ALICE experiments. It is also observed that ν dyn for all the three combinations of particles for semicentral and central collisions, the model predicted values of ν dyn A , B for Pb-Pb collisions at s N N = 2.76 TeV agree fairly well with those observed in the ALICE experiment. For peripheral collisions, however, the model predicted values of ν dyn π , K are somewhat smaller, whereas for p , K and π , p it predicts larger values as compared to the corresponding experimental values. The possible reasons for the observed differences are discussed. The ν dyn values scaled with charged particle density when plotted against N part exhibit a flat behaviour, as expected from the independent particle emission sources. For p , K and π , p combinations, a departure from the flat trend is, however, observed in central collisions in the case of low p T window when the effect of jet quenching or resonances is considered. Furthermore, the study of ν dyn A , B dependence on particle density for various collision systems (including proton-proton collisions) suggests that at LHC energies ν dyn values for a given particle pair are simply a function of charged particle density, irrespective of system size, beam energy, and collision centrality.

Jet fragmentation transverse momentum distributions in pp and p-Pb collisions at $$ \sqrt{s} $$, $$ \sqrt{s_{\mathrm{NN}}} $$ = 5.02 TeV

Jet fragmentation transverse momentum (jT) distributions are measured in proton-proton (pp) and proton-lead (p-Pb) collisions at $$ \sqrt{s_{\mathrm{NN}}} $$ s NN = 5.02 TeV with the ALICE experiment at the LHC. Jets are reconstructed with the ALICE tracking detectors and electromagnetic calorimeter using the anti-kT algorithm with resolution parameter R = 0.4 in the pseudorapidity range |η| < 0.25. The jT values are calculated for charged particles inside a fixed cone with a radius R = 0.4 around the reconstructed jet axis. The measured jT distributions are compared with a variety of parton-shower models. Herwig and Pythia 8 based models describe the data well for the higher jT region, while they underestimate the lower jT region. The jT distributions are further characterised by fitting them with a function composed of an inverse gamma function for higher jT values (called the “wide component”), related to the perturbative component of the fragmentation process, and with a Gaussian for lower jT values (called the “narrow component”), predominantly connected to the hadronisation process. The width of the Gaussian has only a weak dependence on jet transverse momentum, while that of the inverse gamma function increases with increasing jet transverse momentum. For the narrow component, the measured trends are successfully described by all models except for Herwig. For the wide component, Herwig and PYTHIA 8 based models slightly underestimate the data for the higher jet transverse momentum region. These measurements set constraints on models of jet fragmentation and hadronisation.

Measurement of beauty and charm production in pp collisions at $$ \sqrt{s} $$ = 5.02 TeV via non-prompt and prompt D mesons

The pT-differential production cross sections of prompt and non-prompt (produced in beauty-hadron decays) D mesons were measured by the ALICE experiment at midrapidity (|y|< 0.5) in proton-proton collisions at $$ \sqrt{s} $$ s = 5.02 TeV. The data sample used in the analysis corresponds to an integrated luminosity of (19.3 ± 0.4) nb−1. D mesons were reconstructed from their decays D0→ K−π+, D+→ K−π+π+, and $$ {\mathrm{D}}_{\mathrm{s}}^{+}\to \upphi {\uppi}^{+}\to {\mathrm{K}}^{-}{\mathrm{K}}^{+}{\uppi}^{+} $$ D s + → ϕ π + → K − K + π + and their charge conjugates. Compared to previous measurements in the same rapidity region, the cross sections of prompt D+ and $$ {\mathrm{D}}_{\mathrm{s}}^{+} $$ D s + mesons have an extended pT coverage and total uncertainties reduced by a factor ranging from 1.05 to 1.6, depending on pT, allowing for a more precise determination of their pT-integrated cross sections. The results are well described by perturbative QCD calculations. The fragmentation fraction of heavy quarks to strange mesons divided by the one to non-strange mesons, fs/(fu + fd), is compatible for charm and beauty quarks and with previous measurements at different centre-of-mass energies and collision systems. The $$ \mathrm{b}\overline{\mathrm{b}} $$ b b ¯ production cross section per rapidity unit at midrapidity, estimated from non-prompt D-meson measurements, is $$ \mathrm{d}{\sigma}_{\mathrm{b}\overline{\mathrm{b}}}/\mathrm{d}y\left|{}_{\left|\mathrm{y}\right|<0.5}=34.5\pm 2.4{\left(\mathrm{stat}\right)}_{-2.9}^{+4.7}\left(\mathrm{tot}.\mathrm{syst}\right)\right. $$ d σ b b ¯ / d y y < 0.5 = 34.5 ± 2.4 stat − 2.9 + 4.7 tot . syst μb. It is compatible with previous measurements at the same centre-of-mass energy and with the cross section pre- dicted by perturbative QCD calculations.

Event Shape and Multiplicity Dependence of Freeze-Out Scenario and System Thermodynamics in Proton+Proton Collisions at s = 13 TeV Using PYTHIA8

Recent observations of QGP-like conditions in high-multiplicity pp collisions from ALICE experiment at the LHC warrant an introspection whether to use pp collisions as a baseline measurement to characterize heavy-ion collisions for the possible formation of a Quark-Gluon Plasma. A double differential study of the particle spectra and thermodynamics of the produced system as a function of charged-particle multiplicity and transverse spherocity in pp collisions would shed light on the underlying event dynamics. Transverse spherocity, one of the event shape observables, allows to separate the events in terms of jetty and isotropic events. We analyse the identified particle transverse momentum ( p T ) spectra as a function of charged-particle multiplicity and transverse spherocity using Tsallis nonextensive statistics and Boltzmann-Gibbs Blast-Wave (BGBW) model in pp collisions at s = 13 TeV using PYTHIA8 event generator. The extracted parameters such as temperature ( T ), radial flow ( β ), and nonextensive parameter ( q ) are shown as a function of charged-particle multiplicity for different spherocity classes. We observe that the isotropic events approach thermal equilibrium while the jetty ones remain far from equilibrium. We argue that, while studying the QGP-like conditions in small systems, one should separate the isotropic events from the spherocity-integrated events, as the production dynamics are different.