Left: Combined tracking efficiency and acceptance as a function of \pT for pp, p--Pb, central (0-5\%) and peripheral (70--80\%) Pb--Pb collisions determined using Monte Carlo simulations and a reweighting method (see text for details). For better visibility, the curves for p--Pb and Pb--Pb are offset by the indicated values. The effect of the reweighting on the efficiency corrections is shown in the bottom panel. The systematic uncertainties of the reweighting ($< 2.4\%$) are not shown Right: Contamination from secondary particles estimated from Monte Carlo simulations and from the impact parameter fits in data (see text for details). The effect of the reweighting of secondary particles is shown in the bottom panel. The systematic uncertainties on the scaling factors ($< 20\%$) are not shown.