Event-by-Event Identified Particle Ratio Fluctuations in Pb–Pb Collisions with ALICE using the Identity Method

Arslandok, M. and Adam, J. and Adamová, D. and Aggarwal, M. M. and Aglieri, Rinella G. and Agnello, M. and Agrawal, N. and Ahammed, Z. and Ahn, S. U. and Aiola, S. and Akindinov, A. and Alam, S. N. and Aleksandrov, D. and Alessandro, B. and Alexandre, D. and Alfaro, Molina R. and Alici, A. and Alkin, A. and Almaraz, JRM and Alme, J. and Alt, T. and Altinpinar, S. and Altsybeev, I. and Alves, Garcia Prado C. and Andrei, C. and Andronic, A. and Anguelov, V. and Anielski, J. and Antičić, T. and Antinori, F. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Bíró, Gábor and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Kiss, Gábor and Varga-Kőfaragó, Mónika and Lévai, Péter and Oláh, László and Pochybova, Sona (2016) Event-by-Event Identified Particle Ratio Fluctuations in Pb–Pb Collisions with ALICE using the Identity Method. NUCLEAR PHYSICS A, 956. pp. 870-873. ISSN 0375-9474

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Abstract

The study of event-by-event fluctuations of identified hadrons may reveal the degrees of freedom of the strongly interacting matter created in heavy-ion collisions and the underlying dynamics of the system. The observable νdyn, which is defined in terms of the moments of identified-particle multiplicity distributions, is used to quantify the magnitude of the dynamical fluctuations in event-by-event measurements of particle ratios. The ALICE detector at the LHC is well-suited for the study of νdyn, due to its excellent particle identification capabilities. Particle identification based on the measurement of the specific ionisation energy loss, dE/dx, works well on a statistical basis but suffers from ambiguities when applied on an event-by-event level. A novel experimental technique called the ”Identity Method” is used to overcome such limitations. The first results on identified particle ratio fluctuations in Pb-Pb collisions at √sNN =2.76 TeV in ALICE as a function of centrality are presented. The ALICE results for the most peripheral events indicate an increasing correlation between pions and protons which is not reproduced by the HIJING and AMPT models. On the other hand, for the most central events the ALICE results agree with the extrapolations based on the data at lower energies from CERN-SPS and RHIC.

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