Measurement of the charged-hadron spectra and nuclear modification factor in lead-lead collisions with the ATLAS detector
Abstract
The ATLAS experiment at the Large Hadron Collider (LHC) measures charged hadron spectra obtained in 2010 and 2011 lead-lead LHC data taking periods with total integrated statistics of 0.15 nb(-1). The results are compared to the pp spectra of charged hadrons at the same centre-of-mass energy based on the data sample with integrated luminosity of 4.2 pb(-1) obtained by the ATLAS experiment in 2011 and 2013.
This allows a detailed comparison of the two collision systems in a wide transverse momentum (0.5 < p(T) < 150 GeV) and pseudorapidity (vertical bar eta vertical bar < 2) ranges in different centrality intervals of Pb+Pb collision. The nuclear modification factor R-AA is presented in detail as a function of centrality, p(T) and eta.
It shows a distinct p(T)-dependence with a pronounced minimum at about 7 GeV. Above 60 GeV, it is consistent with a flat, centrality-dependent, value within the uncertainties.
The value is 0.55 +/- 0.01(stat.) +/- 0.04(syst.) in the most central collisions. The R-AA is observed to be consistent with flat vertical bar eta vertical bar dependence over the whole transverse momentum range in all centrality classes.