Abstract
In this thesis, measurements of the pT-differential production yields of prompt D*+-meson in Pb--Pb collisions in the two centrality classes 0--10% and 30--50% at a center-of-mass energy per nucleon pair $sqrt{s_{rm NN}} = 5.02$ TeV are presented. The high statistic data sample collected at the end of 2018 by the
... read more
ALICE collaboration, allows us to perform the measurements in finer pT bins for transverse momentum range lower than 10 GeV/c. Moreover, the average non-strange D-meson RAA (nuclear modification factor) as a function of pT can go down to 0 pT at 0--10% centrality classes. The new sample grants an improvement in statistical precision of the order of 3, with respect to 2015 data, opening for the possibility of a more detailed comparison of the non-strange D mesons RAA with the light flavour sector (pions), the strange sector (Ds and with theoretical models including collisional and radiative energy loss. On the comparison with the light flavour sector, we showed a largely significative difference between the RAA of charged pions and D mesons in the low pT region. Such difference would be naively expected in case of mass dependence of the in medium energy loss. However, while striking, this difference can not be directly used to claim a mass dependence due to several factors that can play a role in defining the shape of the RAA in such pT region (i.e. cold-nuclear matter effect, fragmentation). Therefore theoretical calculations are mandatory to draw, once compared with data, more firm conclusions.
The nuclear modification factor (RAA) measurements with the latest Pb--Pb data show that radiative and collisional energy loss are needed to explain the non-strange D-meson nuclear modification factor. Radiative processes are successful to describe the RAA at high pT while at low pT it is well reproduced by collisional processes with an exchange of importance among the two processes around 5--8 GeV/c. The comparison between the non-strange and strange D mesons with model predictions indicates that hadronisation mechanism of c-quark via recombination in the Quark-Gluon Plasma (QGP) takes place. It means that the hadrons are produced by recombining the quarks which are collectively moving in the QGP medium. In particular, the TAMU model reproduces well the Ds-meson enhancement with respect to the average non-strange D-meson RAA for pT < 10 GeV/c, which is expected in case of hadronisation via coalescence due to the enhanced production of strange quarks in the QGP.
show less
