Centrality dependence of the pseudorapidity density distribution for charged particles in Pb-Pb collisions at √sNN=2.76TeV

Abbas, E. and Abelev, B. and Adam, J. and Adamová, D. and Adare, A. M. and Aggarwal, M. M. and Aglieri, Rinella G. and Agnello, M. and Agócs, András and Agostinelli, A. and Ahammed, Z. and Ahmad, Masoodi A. and Ahmad, N. and Ahn, S. U. and Ahn, S. A. and Aimo, I. and Ajaz, M. and Akindinov, A. and Aleksandrov, D. and Alessandro, B. and Alici, A. and Alkin, A. and Almaráz, Aviña E. and Alme, J. and Alt, T. and Altini, V. and Altinpinar, S. and Altsybeev, I. and Andrei, C. and Andronic, A. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Lévai, Péter and Molnár, Levente and Pochybova, Sona (2013) Centrality dependence of the pseudorapidity density distribution for charged particles in Pb-Pb collisions at √sNN=2.76TeV. PHYSICS LETTERS B, 726 (4-5). pp. 610-622. ISSN 0370-2693

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Abstract

We present the first wide-range measurement of the charged-particle pseudorapidity density distribution, for different centralities (the 0–5%, 5–10%, 10–20%, and 20–30% most central events) in Pb–Pb collisions at √ sNN = 2.76TeV at the LHC. The measurement is performed using the full coverage of the ALICE detectors, −5.0 < η < 5.5, and employing a special analysis technique based on collisions arising from LHC ‘satellite’ bunches. We present the pseudorapidity density as a function of the number of participating nucleons as well as an extrapolation to the total number of produced charged particles (Nch = 17165 ± 772 for the 0–5% most central collisions). From the measured dNch/dη distribution we derive the rapidity density distribution, dNch/dy, under simple assumptions. The rapidity density distribution is found to be significantly wider than the predictions of the Landau model. We assess the validity of longitudinal scaling by comparing to lower energy results from RHIC. Finally the mechanisms of the underlying particle production are discussed based on a comparison with various theoretical models.

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