Top panel: Ratio of differential cross sections of charged particles in INEL pp collisions at different collision energies as a function of $p_{\rm T}$. Grey boxes denote $p_{\rm T}$ dependent systematic uncertainties. Normalization uncertainties are not shown (see text for details). The histograms show the same ratio determined from NLO calculations.
Bottom panel: Ratio of data and NLO derived from upper panel. A variation of the scale of the NLO gives a systematic uncertainty on the double ratio of 0.5--23.6% for $0.9$ TeV / $2.76$ TeV, 1.0-37.8% for $0.9$ TeV / $7$ TeV and 2.4-12.3% for $2.76$ TeV / $7$ TeV.