Bulk observables at 5.02 TeV using quasiparticle anisotropic hydrodynamics

We compare predictions of 3+1D quasiparticle anisotropic hydrodynamics (aHydroQP) for a large set of bulk observables with experimental data collected in 5.02 TeV Pb–Pb collisions. We make predictions for identified hadron spectra, identified hadron average transverse momentum, charged particle multiplicity as a function of pseudorapidity, the kaon-to-pion ($$K/\pi $$ K / π ) and proton-to-pion ($$p/\pi $$ p / π ) ratios, identified particle and charged particle elliptic flow, and HBT radii. We compare to data collected by the ALICE collaboration in 5.02 TeV Pb–Pb collisions. We find that, based on available data, these bulk observables are well described by aHydroQP with an assumed initial central temperature of $$T_0=630$$ T 0 = 630 MeV at $$\tau _0 = 0.25$$ τ 0 = 0.25 fm/c and a constant specific shear viscosity of $$\eta /s=0.159$$ η / s = 0.159 , which corresponds to a peak specific bulk viscosity of $$\zeta /s = 0.048$$ ζ / s = 0.048 . In particular, we find that the momentum dependence of the kaon-to-pion ($$K/\pi $$ K / π ) and proton-to-pion ($$p/\pi $$ p / π ) ratios reported recently by the ALICE collaboration are extremely well described by aHydroQP in the 0–5% centrality class.

Production of light flavored charged hadron in pp collisions at 900 GeV with hadron production models

Differential yields of light flavored charged hadrons in [Formula: see text] collision at 0.9 TeV in the transverse momentum [Formula: see text] ranging from 0.1–2.5 GeV/c with pseudorapidity [Formula: see text] are presented here. The spectra obtained by Monte Carlo simulations with event generators — EPOS 1.99, EPOS-LHC, QGSJETII-04 and Sibyll2.3c — are compared with the ALICE measurements. For [Formula: see text] mesons, EPOS1.99, EPOS-LHC and QGSJETII-04 described the ALICE measurement very well almost in the entire [Formula: see text] range except QGSJETII-04 which underpredicts with [Formula: see text] below 0.4 GeV/c. The Sibyll2.3c model slightly overpredicts for [Formula: see text] GeV/c and underpredicts afterwards. For [Formula: see text] mesons, all models describe the experimental data qualitatively, except at high [Formula: see text], where the models slightly underpredict. The EPOS-LHC and QGSJETII-04 models, at low [Formula: see text], describe the distribution of the experimental measurements very well in both cases of protons and anti-protons, whereas the former underpredicts and the latter overpredicts at higher [Formula: see text]. The EPOS1.99 overpredicts at low [Formula: see text] below 1 GeV/c, whereas it reproduces the results well above it. Sibyll2.3c overpredicts the distribution over the entire range of [Formula: see text]. Models described the average transverse momentum [Formula: see text] of these hadron species as a function of their mass, showing small rise in the average [Formula: see text] with the mass of the particles. The same has been observed by the STAR collaboration with measurements in [Formula: see text] reactions at [Formula: see text] = 200 GeV and also in [Formula: see text] collisions at [Formula: see text] = 900 GeV.

Recent developments in particle yield fluctuation measurements

In relativistic heavy-ion collisions, properties of the initial state and effects arising during evolution of the medium, such as a transition between the hadronic and partonic phases, should reflect themselves in event-by-event fluctuations of the number of produced particles. In this paper, recentmeasurements of several event-by-event observables, namely, dynamical fluctuations of relative particle yields and forwardbackward correlations of different types, are discussed. Also, new observables for forward-backward correlation studies are proposed: correlations between ratios of identified particle yields in two separated acceptance intervals and the correlation between the ratio in one interval and average transverse momentum in another.