Nuclear modification factor for charged particle production at high pT in PbPb collisions at sqrt(sNN)=2.76 TeV

The transverse momentum ($p_{\mathrm{T}}$) spectra of charged particles is measured as a function of collision centrality in PbPb collisions at $\sqrt{s_{_{NN}}}=2.76$\,\text{Te\hspace{-.08em}V}. The results are compared to a pp reference spectrum, constructed by interpolation between $\sqrt{s}=0.9$ and 7\,\text{Te\hspace{-.08em}V} measurements. The nuclear modification factor ($R_{\mathrm{AA}}$) is constructed by dividing the PbPb $p_{\mathrm{T}}$ spectrum, normalized to the number of binary collisions ($N_{\mathrm{coll}}$), by the pp spectrum. As seen at lower energies, the charged particle spectrum in central PbPb collisions is suppressed by at least a factor of five ($R_{\mathrm{AA}} < 0.2$) compared to binary scaling around $p_{\mathrm{T}}=5$--10\ensuremath{{\,\text{Ge\hspace{-.08em}V\hspace{-0.16em}/\hspace{-0.08em}}c}}. Above $p_{\mathrm{T}}=10$\ensuremath{{\,\text{Ge\hspace{-.08em}V\hspace{-0.16em}/\hspace{-0.08em}}c}}, however, there is a significant rise in the nuclear modification factor, which reaches $R_{\mathrm{AA}} \approx 0.5$ at $p_{\mathrm{T}}=40$\ensuremath{{\,\text{Ge\hspace{-.08em}V\hspace{-0.16em}/\hspace{-0.08em}}c}}.