Nuclear modification factors of prompt D mesons as a function of $\pt$ in 0--10\%, 10--20\%, 20--40\%, 40--60\%, and 60--100\% centrality classes compared with those of charged particles  The vertical bars represent the statistical uncertainties while the empty boxes and the shaded boxes represent the systematic uncertainties for the prompt D mesons and for the charged particles. The colour-filled boxes at $\QpPb$ $=1$ represent the normalisation uncertainties on the $\langle \TpPb \rangle$ .