Measurement of D$^{+}$ meson production in p-Pb collisions with the ALICE detector

Abstract

The main goal of the experimental programs on ultra-relativistic heavy ion collisions at the LHC is the production and characterization of the Quark Gluon Plasma (QGP), a phase of nuclear matter in which strongly interacting constituents (quarks and gluons) are deconfined. Heavy quarks are considered effective probes of the properties of the QGP as they are created on a short time scale, with respect to that of the QGP, and subsequently interact with it. Moreover, for a proper assessment of the characteristics of the matter produced in heavy-ion collisions, it is important to disentangle the final state effects due to the formation of a QGP from the initial state effects due to the fact that nuclei are present in the colliding system. Both initial and final state effects may lead to qualitatively similar phenomena in the observables of interest. The measurement of charmed meson production in proton-nucleus collisions allows to assess initial state effects present in nuclear collisions, under the assumption that an extended deconfined medium is not created in this kind of interactions. The nuclear modification factor of $D$ mesons in p-Pb collisions ($R_{\rm pPb}$) is essential for a complete understanding of the modification of $D$ mesons momentum distributions observed in Pb-Pb collisions at $\sqrt{s_{\rm NN}}$= 2.76 TeV, which is interpreted as due to the $c$-quark energy loss in the medium. In addition, some of the results obtained from high-multiplicity p-Pb collisions at LHC, such as the ridge structure in the two-particle correlation function, turned out to be unexpected, and have been interpreted in terms of final state effects such as hydrodynamic flow. These aspects make a study of charmed meson production in p-Pb collisions as a function of the event multiplicity of great interest.