Centrality Dependence of Charged Particle Production at Large Transverse Momentum in Pb$-$Pb Collisions at $\sqrt{s_{NN}}=2.76$ TeV.

Submission Date: 
11/09/2012
Article Information
Submission Form
System: 
p-p
System: 
Pb-Pb
Energy: 
2.76 TeV
Abstract Plain Text: 

 

The inclusive transverse momentum ($p_{\rm t}$) distributions of
primary charged particles are measured in the pseudo-rapidity range
$|\eta|<0.8$ as a function of event centrality in Pb$-$Pb collisions
at $\sqrt{s_{\rm{NN}}} = 2.76$~TeV with ALICE at the LHC.  The data
are presented in the transverse momentum range $0.15<p_{\rm
t}<50$~GeV/c for nine centrality intervals (from the most central
0--5\% to the most peripheral 70--80\% collisions). 
The Pb--Pb spectra are presented in terms of the nuclear
modification factor $R_{\rm{AA}}$ using a pp reference spectrum measured with ALICE at the same collision energy. We observe that the suppression
pattern of high-$p_{\rm t}$ particles strongly depends on event
centrality. In central collisions (0--5\%) the yield is most strongly
suppressed ($R_{\rm{AA}} \approx0.13$) at $p_{\rm t}=6-7$~GeV/c. 
Above $p_{\rm t}=7$~GeV/c, there is a
significant rise in the nuclear modification factor, which reaches
$R_{\rm{AA}} \approx 0.4$ at $p_{\rm t}=30$~GeV/c. In peripheral
collisions (70--80\%), the suppression is weaker with $R_{\rm{AA}} \approx
0.7$ almost independent of $p_{\rm t}$. The measured $R_{\rm{AA}}$ in
0--5\% central collisions is compared to model calculations.