Abstract
First results on hbox {K}/pi , hbox {p}/pi and K/p fluctuations are obtained with the ALICE detector at the CERN LHC as a function of centrality in text{ Pb--Pb } collisions at sqrt{s_mathrm{{NN}}} =2.76hbox { TeV}. The observable nu _{mathrm{dyn}}, which is defined in terms of the moments of particle multiplicity distributions, is used to quantify the magnitude of dynamical fluctuations of relative particle yields and also provides insight into the correlation between particle pairs. This study is based on a novel experimental technique, called the Identity Method, which allows one to measure the moments of multiplicity distributions in case of incomplete particle identification. The results for hbox {p}/pi show a change of sign in nu _{mathrm{dyn}} from positive to negative towards more peripheral collisions. For central collisions, the results follow the smooth trend of the data at lower energies and nu _{mathrm{dyn}} exhibits a change in sign for hbox {p}/pi and K/p.
Highlights
The theory of strong interactions, Quantum Chromodynamics (QCD), predicts that at sufficiently high energy density nuclear matter transforms into a deconfined state of quarks and gluons known as Quark–Gluon Plasma (QGP) [1,2]
Values of νdyn, scaled by the charged-particle density at midrapidity dNch/dη, exhibit finite variations with collision centrality. This is in contrast to predictions by HIJING, which, for all three pair combinations, show essentially constant as well as positive values
The evolution of νdyn with collision energy shows that the particle production dynamics changes significantly from that observed at lower energies
Summary
The theory of strong interactions, Quantum Chromodynamics (QCD), predicts that at sufficiently high energy density nuclear matter transforms into a deconfined state of quarks and gluons known as Quark–Gluon Plasma (QGP) [1,2]. One of the possible signatures of a transition between the hadronic and partonic phases is the enhancement of fluctuations of the number of produced particles in the hadronic final state of relativistic heavy-ion collisions [3,4,5]. A correlation analysis of event-by-event abundances of pions, kaons and protons produced in Pb–Pb collisions at LHC energies may provide a connection to fluctuations of globally conserved quantities such as electric charge, strangeness and baryon number, and shed light on the phase structure of strongly interacting matter [6]. The νdyn[ A, B]1 fluctuation measure contrasts the relative strength of fluctuations of species A and B to the relative strength of correlations between these two species It vanishes when the particles A and B are produced in a statistically independent way [8,9]
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