Abstract
Measurements of event-by-event fluctuations of charged-particle multiplicities in Pb–Pb collisions at sqrt{s_{mathrm {NN}}} = 2.76 TeV using the ALICE detector at the CERN Large Hadron Collider (LHC) are presented in the pseudorapidity range |eta |<0.8 and transverse momentum 0.2< p_{mathrm{T}} < 2.0 GeV/c. The amplitude of the fluctuations is expressed in terms of the variance normalized by the mean of the multiplicity distribution. The eta and p_{mathrm{T}} dependences of the fluctuations and their evolution with respect to collision centrality are investigated. The multiplicity fluctuations tend to decrease from peripheral to central collisions. The results are compared to those obtained from HIJING and AMPT Monte Carlo event generators as well as to experimental data at lower collision energies. Additionally, the measured multiplicity fluctuations are discussed in the context of the isothermal compressibility of the high-density strongly-interacting system formed in central Pb–Pb collisions.
Highlights
The measured multiplicity scales with the collision centrality in heavy-ion collisions
Npart for the two models are shifted for better visibility
The systematic uncertainties are presented as filled boxes participants, Npart, obtained from Ref. [38], are smaller than the width of the solid red circles used to present the data in the centrality range considered in this measurement
Summary
The measured multiplicity scales with the collision centrality in heavy-ion collisions. Measurements of the scaled variance of multiplicity fluctuations are presented a√ssaNNfu=nc2ti.o7n6 of collision centrality TeV using the ALICE in Pb–Pb collisions detector at the LHC. In the wounded nucleon model, nucleus–nucleus (such as Pb–Pb) collisions are considered to be a superposition of individual nucleon–nucleon interactions In this context, the fluctuations in multiplicity within a given centrality window arise in part from fluctuations in Npart and from fluctuations in the number of particles (n) produced by each nucleon– nucleon interaction [22,26,31]. Where n is the average number of particles produced by each nucleon–source within the detector acceptance, ωn is the scaled variance of the fluctuations in n, and ωNpart denotes the fluctuations in Npart. The extracted values of ωNpart are corrected for the effects of the finite width of the centrality intervals
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