Scaling Properties of Multiplicity Fluctuations in the AMPT Model

From the events generated from the MC code of a multi-phase transport (AMPT) model with string melting, the properties of multiplicity fluctuations of charged particles in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}=\rm{~2.76 \,TeV}$ are studied. Normalized factorial moments, $F_{q}$, of spatial distributions of the particles have been determined in the framework of intermittency. Those moments are found in some kinematic regions to exhibit scaling behavior at small bin sizes, but not in most regions. However, in relating $F_{q}$ to $F_{2}$ scaling behavior is found in nearly all regions. The corresponding scaling exponents, $\nu$, determined in the low transverse momentum ($p_{\rm{T}}$) region $\le$ 1.0 GeV/c are observed to be independent of the $p_{\rm{T}}$ bin position and width. The value of $\nu$ is found to be larger than 1.304, which is the value that characterizes the Ginzburg-Landau type second order phase transition. Thus there is no known signature for phase transition in the AMPT model. This study demonstrates that, for the system under investigation, the method of analysis is effective in extracting features that are relevant to the question of whether the dynamical processes leading phase transition are there or not.Comment: 6 pages, 5 figure

Intermittency study of charged particles generated in Pb-Pb collisions at sNN= 2.76 TeV\sqrt{s_{\mathrm{NN}}}\text{= 2.76 TeV} using EPOS3

Charged particle multiplicity fluctuations in Pb-Pb collisions are studied for the central events generated using EPOS3 (hydro and hydro+cascade) at $\sqrt{s_{\mathrm{NN}}}\text{ = 2.76 TeV}$. Intermittency analysis is performed in the mid-rapidity region in two-dimensional ($\eta$, $\phi$) phase space within the narrow transverse momentum (p_\rm{{T}}) bins in the low p_\rm{{T}}~region (p_\rm{{T}}~\leq~1.0~GeV/\textit{c}). Power-law scaling of the normalized factorial moments with the number of bins is not observed to be significant in any of the p_\rm{{T}}-bin. Scaling exponent $\nu$, deduced for a few p_\rm{{T}} bins is greater than that of the value 1.304, predicted for the second order phase-transition by the Ginzburg-Landau theory. The link in the notions of fractality is also studied. Fractal dimensions, $D_{q}$ are observed to decrease with the order of the moment $q$ suggesting the multifractal nature of the particle generation in EPOS3.Comment: 7 pages, 8 figure

Normalized factorial moments of spatial distributions of particles in high multiplicity events: A Toy model study

Scaling behavior of normalized factorial moments ($F_{q}$) of spatial distributions of the particles comprising a system may be studied to probe and to determine its characteristics. In heavy-ion collisions at ultra-relativistic energies, a strongly interacting complex system of quarks and gluons is created. The nature of the system created and multi particle production mechanism in these collisions is predicted to be revealed by the study of normalized factorial moments ($F_{{\rm{q}}}$) as function of various parameters. In this work, observations from the Toy model study of the scaling behavior of $F_{{\rm{q}}}$ moments, resilience of these moments to detector efficiencies and sensitivity towards fluctuations in the system will be presented.Comment: 6 pages, 9 figure

Azimuthal anisotropy of charged jet production in root s(NN)=2.76 TeV Pb-Pb collisions

We present measurements of the azimuthal dependence of charged jet production in central and semi-central root s(NN) = 2.76 TeV Pb-Pb collisions with respect to the second harmonic event plane, quantified as nu(ch)(2) (jet). Jet finding is performed employing the anti-k(T) algorithm with a resolution parameter R = 0.2 using charged tracks from the ALICE tracking system. The contribution of the azimuthal anisotropy of the underlying event is taken into account event-by-event. The remaining (statistical) region-to-region fluctuations are removed on an ensemble basis by unfolding the jet spectra for different event plane orientations independently. Significant non-zero nu(ch)(2) (jet) is observed in semi-central collisions (30-50% centrality) for 20 <p(T)(ch) (jet) <90 GeV/c. The azimuthal dependence of the charged jet production is similar to the dependence observed for jets comprising both charged and neutral fragments, and compatible with measurements of the nu(2) of single charged particles at high p(T). Good agreement between the data and predictions from JEWEL, an event generator simulating parton shower evolution in the presence of a dense QCD medium, is found in semi-central collisions. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B.V. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/).Peer reviewe

Production of He-4 and (4) in Pb-Pb collisions at root(NN)-N-S=2.76 TeV at the LHC

Results on the production of He-4 and (4) nuclei in Pb-Pb collisions at root(NN)-N-S = 2.76 TeV in the rapidity range vertical bar y vertical bar <1, using the ALICE detector, are presented in this paper. The rapidity densities corresponding to 0-10% central events are found to be dN/dy4(He) = (0.8 +/- 0.4 (stat) +/- 0.3 (syst)) x 10(-6) and dN/dy4 = (1.1 +/- 0.4 (stat) +/- 0.2 (syst)) x 10(-6), respectively. This is in agreement with the statistical thermal model expectation assuming the same chemical freeze-out temperature (T-chem = 156 MeV) as for light hadrons. The measured ratio of (4)/He-4 is 1.4 +/- 0.8 (stat) +/- 0.5 (syst). (C) 2018 Published by Elsevier B.V.Peer reviewe

Forward-central two-particle correlations in p-Pb collisions at root s(NN)=5.02 TeV

Two-particle angular correlations between trigger particles in the forward pseudorapidity range (2.5 2GeV/c. (C) 2015 CERN for the benefit of the ALICE Collaboration. Published by Elsevier B. V.Peer reviewe

Event-shape engineering for inclusive spectra and elliptic flow in Pb-Pb collisions at root(NN)-N-S=2.76 TeV

Peer reviewe