Effects of the initial-state geometry on D-meson production in pp and pPb collisions

Going from lower to higher multiplicity events in proton-proton and proton-lead collisions, the data show a stronger than linear growth of the D-meson normalized yields. In this contribution we try to understand this behavior using a Monte Carlo event generator which implements the $k_T$-factorization formalism. We use different spatial distribution of matter in the proton and in the lead nucleus at the initial stage of these collisions. We find that, with all the tested spatial distributions, the model reproduces well the behavior seen in the data. We conclude that this observable is not appropriate for a detailed study of the spatial distribution of matter in the proton.