KS0 and Λ production in Pb-Pb collisions at √s NN=2.76 TeV

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, N. and Ahmad, Masoodi A. and Ahmed, I. and Ahn, S. U. and Ahn, S. A. and Aimo, I. and Aiola, S. and Ajaz, M. and Akindinov, A. and Aleksandrov, D. and Alessandro, B. and Alexandre, D. and Alici, A. and Alkin, A. and Alme, J. and Alt, T. and Altini, V. and Altinpinar, S. and Altsybeev, I. and Alves, Garcia Prado C. and Barnaföldi, Gergely Gábor and Bencédi, Gyula and Berényi, Dániel and Boldizsár, László and Dénes, Ervin and Hamar, Gergő and Kiss, Gábor and Lévai, Péter and Molnár, Levente and Oláh, László and Pochybova, Sona (2013) KS0 and Λ production in Pb-Pb collisions at √s NN=2.76 TeV. PHYSICAL REVIEW LETTERS, 111 (22). ISSN 0031-9007

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Abstract

The ALICE measurement of K 0S and Λ production at mid-rapidity in Pb–Pb collisions at √sNN = 2 .76 TeV is presented. The transverse momentum (p T) spectra are shown for several collision centrality intervals and in the pT range from 0.4 GeV/c (0.6 GeV/c for Λ) to 12 GeV/c. The pT dependence of the Λ / K 0S ratios exhibits maxima in the vicinity of 3 GeV/c, and the positions of the maxima shift towards higher p T with increasing collision centrality. The magnitude of these maxima increases by almost a factor of three between most peripheral and most central Pb–Pb collisions. This baryon excess at intermediate p T is not observed in pp interactions at √s = 0 .9 TeV and at √s = 7 TeV. Qualitatively, the baryon enhancement in heavy-ion collisions is expected from radial flow. However, the measured pT spectra above 2 GeV/c progressively decouple from hydrodynamical-model calculations. For higher values of p T, models that incorporate the influence of the medium on the fragmentation and hadronization processes describe qualitatively the p T dependence of the Λ / K 0S ratio.

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