Skewness and kurtosis of mean transverse momentum fluctuations at the LHC energies

Abstract

The first measurements of skewness and kurtosis of mean transverse momentum ($⟨p_{\mathrm{T}}⟩$) fluctuations are reported in Pb$-$Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV, Xe$-$Xe collisions at $\sqrt{s_{\mathrm{NN}}}$ $=$ 5.44 TeV and pp collisions at $\sqrt{s}=5.02$ TeV using the ALICE detector. The measurements are carried out as a function of system size $⟨\mathrm{d}{N}_{\mathrm{ch}}/\mathrm{d}\eta {⟩}_{|\eta |<0.5}^{1/3}$, using charged particles with transverse momentum ($p_{\mathrm{T}}$) and pseudorapidity ($\eta$), in the range $0.2<p_{\mathrm{T}}<3.0$ GeV/$c$ and $|\eta |<0.8$, respectively. In Pb$-$Pb and Xe$-$Xe collisions, positive skewness is observed in the fluctuations of $⟨p_{\mathrm{T}}⟩$ for all centralities, which is significantly larger than what would be expected in the scenario of independent particle emission. This positive skewness is considered a crucial consequence of the hydrodynamic evolution of the hot and dense nuclear matter created in heavy-ion collisions. Furthermore, similar observations of positive skewness for minimum bias pp collisions are also reported here. Kurtosis of $⟨p_{\mathrm{T}}⟩$ fluctuations is found to be in good agreement with the kurtosis of Gaussian distribution, for most central Pb$-$Pb collisions. Hydrodynamic model calculations with MUSIC using Monte Carlo Glauber initial conditions are able to explain the measurements of both skewness and kurtosis qualitatively from semicentral to central collisions in Pb--Pb system. Color reconnection mechanism in PYTHIA8 model seems to play a pivotal role in capturing the qualitative behavior of the same measurements in pp collisions.

arXiv comment24 pages, 5 captioned figures, 1 table, authors from page 18, published version, figures at http://alice-publications.web.cern.ch/node/9598

References in corpus (40)

• PYTHIA 6.4 Physics and Manual
• PYTHIA 6.2 Physics and Manual
• An Introduction to PYTHIA 8.2
• A Multi-Phase Transport Model for Relativistic Heavy Ion Collisions
• The Color Glass Condensate
• Performance of the ALICE Experiment at the CERN LHC
• Event-by-Event Fluctuations in Heavy Ion Collisions and the QCD Critical Point
• The ALICE TPC, a large 3-dimensional tracking device with fast readout for ultra-high multiplicity events
• 3+1D hydrodynamic simulation of relativistic heavy-ion collisions
• New Developments in Relativistic Viscous Hydrodynamics
• Alternative ansatz to wounded nucleon and binary collision scaling in high-energy nuclear collisions
• Performance of the ALICE VZERO system
• Evolution at small x_bj: The Color Glass Condensate
• Two-pion Bose-Einstein correlations in central Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 2.76 TeV
• Centrality dependence of the charged-particle multiplicity density at mid-rapidity in Pb-Pb collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.02 TeV
• Transverse momentum spectra and nuclear modification factors of charged particles in pp, p-Pb and Pb-Pb collisions at the LHC
• Bulk Viscosity Effects in Event-by-Event Relativistic Hydrodynamics
• Multiplicity dependence of the average transverse momentum in pp, p-Pb, and Pb-Pb collisions at the LHC
• Event-by-event physics in relativistic heavy ion collisions
• The ALICE experiment: a journey through QCD
• The PHOBOS Glauber Monte Carlo
• Event-by-event analysis of heavy ion collisions and thermodynamical fluctuations
• Charged-particle multiplicities in proton-proton collisions at $\sqrt{s}$ = 0.9 to 8 TeV
• Volume Fluctuation and Autocorrelation Effects in the Moment Analysis of Net-proton Multiplicity Distributions in Heavy-Ion Collisions
• Incident energy dependence of pt correlations at relativistic energies
• Thermodynamics of hot strong-interaction matter from ultrarelativistic nuclear collisions
• Transverse momentum spectra and nuclear modification factors of charged particles in Xe-Xe collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.44 TeV
• Centrality and pseudorapidity dependence of the charged-particle multiplicity density in Xe-Xe collisions at $\sqrt{s_{\mathrm{NN}}}$ = 5.44 TeV
• Event-by-event mean $p_{\mathrm{T}}$ fluctuations in pp and Pb-Pb collisions at the LHC
• Charged-particle production as a function of multiplicity and transverse spherocity in pp collisions at $\sqrt{s}$ = 5.02 and 13 TeV
• The viscosity of quark-gluon plasma at RHIC and the LHC
• Baryon Junction Loops in HIJING/BBv2.0 and the Baryon/Meson Anomaly at RHIC
• Fluctuation Probes of Early-Time Correlations in Nuclear Collisions
• Pseudorapidity distributions of charged particles as a function of mid and forward rapidity mutiplicities in pp collisions at $\sqrt{s}$ = 5.02, 7 and 13 TeV
• Skewness of mean transverse momentum fluctuations in heavy-ion collisions
• Update of a Multi-Phase Transport Model with Modern Parton Distribution Functions and Nuclear Shadowing
• Effects of initial state fluctuations on the mean transverse momentum
• Multiplicity and mean transverse momentum fluctuations in Au + Au collisions at RHIC
• Second order relativistic viscous hydrodynamics within an effective description of hot QCD medium
• Thermalization at the femtoscale seen in high-energy Pb+Pb collisions

Cited by in corpus (6)

• Disentangling sources of momentum fluctuations in Xe+Xe and Pb+Pb collisions with the ATLAS detector
• Exploring the Nuclear Shape Phase Transition in Ultra-Relativistic ${}^{129}$Xe+${}^{129}$Xe Collisions at the LHC
• Impact parameter dependence of anisotropic flow: Bayesian reconstruction in ultracentral nucleus-nucleus collisions
• System size and energy dependence of the mean transverse momentum fluctuations at the LHC
• Bayesian reconstruction of anisotropic flow fluctuations at fixed impact parameter
• High-order fluctuations of temperature in hot QCD matter