Centrality Dependence of the Charged-Particle Multiplicity Density at Midrapidity in Pb-Pb Collisions atsNN=2.76  TeV

Abstract

The centrality dependence of the charged-particle multiplicity density at midrapidity in Pb-Pb collisions at ffiffiffiffiffiffiffiffi s NN p ¼ 2:76 TeV is presented. The charged-particle density normalized per participating nucleon pair increases by about a factor of 2 from peripheral (70%-80%) to central (0%-5%) collisions. The centrality dependence is found to be similar to that observed at lower collision energies. The data are compared with models based on different mechanisms for particle production in nuclear collisions.

Centrality dependence of pion freeze-out radii in Pb-Pb collisions atsNN=2.76 TeV

“…The measurement of the average event multiplicity for a given centrality range has a known uncertainty of 3%-4% for all centrality classes [5]. The femtoscopic radii in heavy-ion collisions were observed to scale linearly with dN ch /dη 1/3 at lower collision energies [20].…”

“…The centrality was determined by analyzing the signal from the V0 detector with the procedure described in detail in Ref. [5]. This ensured that the centrality determination was obtained by using particles at significantly different rapidities than the ones used for the pion-correlation analysis.…”

“…In this energy regime, quantum chromodynamics (QCD) predicts the existence of a new state of strongly interacting matter, the quark-gluon plasma (QGP), in which quarks and gluons are no longer confined to individual nucleons. Experimental evidence for the existence of such matter has been found both at the BNL Relativistic Heavy-Ion Collider (RHIC) [1][2][3][4] as well as at the LHC [5][6][7][8][9][10]. The QGP behaves like a fluid with small viscosity and undergoes an explosive expansion.…”

Measurement of event background fluctuations for charged particle jet reconstruction in Pb-Pb collisions at $ \sqrt {{{s_{\text{NN}}}}} = {2}{.76}\,{\text{TeV}} $

“…The VZERO trigger counters are forward scintillator detectors covering a pseudo-rapidity range of 2.8 < η < 5.1 (V0A) and −3.7 < η < −1.7 (V0C). The sum of VZERO amplitudes is also used as a measure of event centrality [23]. The SPD consists of two silicon pixel layers at a radial distance to the beam line of r = 3.9 cm and r = 7.6 cm.…”

KS0 and Λ production in charged particle jets in p–Pb collisions at sZhang1 2014Nuclear Physics A5020View full textAdd to dashboardCite

“…For a detailed description of the ALICE detector and its performance, see [17,18]. The event multiplicity classes are determined by the VZERO-A detector (V0A) covering pseudorapidity of 2.8 < η < 5.1 1 A list of members of the ALICE Collaboration and acknowledgements can be found at the end of this issue. in the Pb-going direction.…”