System size dependence of the log-periodic oscillations of transverse momentum spectra ^⋆

¹ Institute of Physics, Jan Kochanowski University, Kielce, Poland
² National Centre for Nuclear Research, Warsaw, Poland

^⋆ Presented by M.Rybczyńnski
^a e-mail: Maciej.Rybczynski@ujk.edu.pl
^b e-mail: Grzegorz.Wilk@fuw.edu.pl
^c e-mail: Zbigniew.Wlodarczyk@ujk.edu.pl

Published online: 24 March 2015

Abstract

Recently the inclusive transverse momentum distributions of primary charged particles were measured for different centralities in Pb + Pb collisions. A strong suppression of the nuclear modification factor in central collisions around p_T ∼ 6 − 7 GeV/c was seen. As a possible explanation, the hydrodynamic description of the collision process was tentatively proposed. However, such effect, (albeit much weaker) also exists in the ratio of data/fits, both in nuclear Pb + Pb collisions, and in the elementary p + p data in the same range of transverse momenta for which such an explanation is doubtful. As shown recently, in this case, assuming that this effect is genuine, it can be attributed to a specific modification of a quasi-power like formula usually used to describe such p_T data, namely the Tsallis distribution. Following examples from other branches of physics, one simply has to allow for the power index becoming a complex number. This results in specific log-periodic oscillations dressing the usual power-like distribution, which can fit the p + p data. In this presentation we demonstrate that this method can also describe Pb + Pb data for different centralities. We compare it also with a two component statistical model with two Tsallis distributions recently proposed showing that data at still larger p_T will be sufficient to discriminate between these two approaches.