Centrality dependence of mid-rapidity charged particles density in relativistic heavy ion collisions – energy scaling

Abstract

Abstract. As far as details on the "Relativistic Heavy Ion Collisions -Expectations, Experimental Facts and Future Plans" lecture could be found on the Summer School web site, the present contribution will summarize the results considered to be of general interest, i.e. the energy scaling of centrality dependence of mid-rapidity charged particles density in relativistic heavy ion collisions, presented in the second part of the lecture, in the section dedicated to the global observables. The comparison of charged particle multiplicity in heavy ion central collisions and e + e − as a function of √ s, including the latest results obtained at LHC in Pb+Pb collisions at 2.76 is followed by the energy scaling of the pseudo-rapidity charged particle density in central rapidity as a function of centrality. IntroductionThe lecture "Relativistic Heavy Ion Collisions -Expectations, Experimental Facts and Future Plans" , accessible on the Summer School web site [1], has three main chapters. An overview of theoretical considerations on which are based the expectations on the properties of matter in extreme conditions of temperature and density which could be obtained in colliding two heavy ions at relativistic and ultra-relativistic energies is presented in the first part. The second part is dedicated to the latest results in the region of high temperature and vanishing chemical potential in Pb + Pb collisions at 2.76 TeV at CERN LHC compared with the previous Au + Au at 0.2 TeV RHIC. Results and expectations evidencing collective type phenomena in high multiplicity and nearly azimuthal isotropic events selected using event shape global observables, Directivity, Sphericity, Trust and Fox-Wolfram moments, in p+p and p+Pb at LHC energies are discussed at the end of this second chapter. In the last chapter is presented the physics program on detailed studies of the QCD phase diagram in the region of highest net baryon density of the CBM experiment at FAIR relative to the recent measurements at RHIC within the beam energy scan program. This chapter ends with a short overview on the main R&D activities in developing highly performant high counting rate Transition Radiation Detectors (TRD) and Multi Strip Multi Gap Resistive Plate Counters (MSMGRPC) for CBM Experiment. Due to the limited number of pages and considering to be a subject of general interest, we decided to concentrate in this written version on the energy scaling of centrality dependence of mid-rapidity charged particles density in relativistic heavy ion collisions, presented in the second part of the lecture, in the section dedicated to the global observables. Pseudo-rapidity charged particle density