Measurement of charged particle $R_{\rm AA}$ at high $p_{\rm T}$ in PbPb collisions at $\sqrt{s_{_{\rm NN}}}=2.76$ TeV with CMS

Charged particle transverse momentum ($p_{\rm T}$) spectra have been measured by CMS for pp and PbPb collisions at the same $\sqrt{s_{_{\rm NN}}}=2.76$~TeV collision energy per nucleon pairs. Calorimeter-based jet triggers are employed to enhance the statistical reach of the high-$p_{\rm T}$ measurements. The nuclear modification factor ($R_{\rm AA}$) is obtained in bins of collision centrality for the PbPb data sample dividing by the measured pp reference spectrum. In the range $p_{\rm T} = 5-10$~GeV/c, the charged particle yield in the most central PbPb collisions is suppressed by up to a factor of 7. At higher $p_{\rm T}$, this suppression is significantly reduced, approaching a factor of 2 for particles with $p_{\rm T} = 40 - 100$~GeV/c.