Centrality dependence ofπ,K, andpproduction in Pb-Pb collisions ats

Abstract

In this paper measurements are presented of π ± , K ± , p, andp production at midrapidity (|y| < 0.5), in Pb-Pb collisions at √ s NN = 2.76 TeV as a function of centrality. The measurement covers the transverse-momentum (p T ) range from 100, 200, and 300 MeV/c up to 3, 3, and 4.6 GeV/c for π , K, and p, respectively. The measured p T distributions and yields are compared to expectations based on hydrodynamic, thermal and recombination models. The spectral shapes of central collisions show a stronger radial flow than measured at lower energies, which can be described in hydrodynamic models. In peripheral collisions, the p T distributions are not well reproduced by hydrodynamic models. Ratios of integrated particle yields are found to be nearly independent of centrality. The yield of protons normalized to pions is a factor ∼1.5 lower than the expectation from thermal models.

Particle production at energies available at the CERN Large Hadron Collider within an evolutionary model

“…At LHC energies the afterburner "post-freeze-out" stage is the longest, and so there is a special interest to check the chemical freeze-out hypotheses within the dynamical models for these energies. The ALICE Collaboration has already noted [8,9] that annihilation processes at the afterburner stage, which are taken into account in the hydrokinetic model (HKM) [10], noticeably improve agreement with (anti)proton spectra/yield at the LHC. The analysis of the role of inelastic processes at the post-hydrodynamic stage in formation of the particle yield is ongoing (see, e.g., [11]).…”

Higher harmonic anisotropic flow of identified particles in Pb–Pb collisions with the ALICE detector

“…π ± and p + p happens at lower p T for mid-peripheral than for the most-central collisions. For the 0-1% centrality range, the crossing point moves to higher p T values for v 2 , since the common velocity field, which exhibits a significant centrality dependence [11], affects heavy particles more. The current study shows that this occurs not only in the case of elliptic flow but also for higher flow harmonics (i.e.…”

Production of π/K/p from intermediate to high pT

“…The transverse momentum, p T , distributions of identified hadrons contain valuable information about the collective expansion of the system (p T 2 GeV/c), the presence of new hadronization mechanisms like quark recombination (2 p T 8 GeV/c) [1] and, at larger transverse momenta, the possible modification of the fragmentation due to the medium [2,3]. ALICE has reported the transverse momentum spectra, as a function of the collision centrality, of charged pions, kaons and (anti)protons from low (hundreds of MeV/c) [4] to high (20 GeV/c) [5] p T . From the analysis of the low p T results in the most central collisions, the radial flow, β T , is found to be ≈ 10% higher than at RHIC, while the kinetic freeze-out temperature was found to be comparable to that extracted from data at RHIC, T kin = 95 MeV [4].…”

“…ALICE has reported the transverse momentum spectra, as a function of the collision centrality, of charged pions, kaons and (anti)protons from low (hundreds of MeV/c) [4] to high (20 GeV/c) [5] p T . From the analysis of the low p T results in the most central collisions, the radial flow, β T , is found to be ≈ 10% higher than at RHIC, while the kinetic freeze-out temperature was found to be comparable to that extracted from data at RHIC, T kin = 95 MeV [4]. The spectra are well described by hydrodynamic models, except the low p T (< 1 GeV/c) proton yield [6][7][8][9].…”