$\pt$-differential production cross section of prompt $\Ds$ mesonswith $|y|< 0.5$ in the interval \mbox{$2< \pt< 12 \gev/c$}, in pp collisions at$\sqrt s =7 \tev$ The cross section is compared to two pQCD calculations:GM-VFNS  (left panel) and a leading order (LO) calculationbased on $k_{\rm T}$-factorisation  (right panel) The ratios of the data to the calculated cross sections are shownin the lower part of each panel. In the data-to-theory ratios the 3.5\%normalisation uncertainty due to the luminosity determination is not includedin the systematic uncertainty on the data points.