Light vector meson production at forward rapidity in pp collisions at √s = 5.02 TeV with ALICE

Among the four fundamental forces, three of them occur at low scale. These three forces are all described in the so-called Standard Model of particles. Among them the force keeping the protons and neutrons bound together, the strong force, is of special interest in this presentation. This force is described by the Quantum Chromo-Dynamics (QCD) theory. Hadrons, such as protons and neutrons, are composed of gluons and quarks. Quarks are kept bound, at least by pairs by the strong force mediated via the gluons and cannot be dissociated. Only in the case of a high energy density (equivalent to high temperature) or at high baryon chemical potential, quarks and gluons can propagate freely, forming a Quark Gluon Plasma (QGP). This state is expected to have existed during the first micro- seconds of the Universe. These extreme conditions can actually be reproduced using heavy-ion collisions at the Large Hadron Collider (LHC). The QGP is expected to be created in the most central heavy ion collisions such as in Pb-Pb collisions at $\sqrt{s_{NN}}$ = 5.02~TeV. Used as a reference, pp collisions where the QGP is not expected to be created are also performed. The QGP can be studied, and its equation of state evaluated investigating the particle yields resulting from these collisions. Different probes of existence of the QGP are studied, in this thesis we investigate the low mass vector mesons with the dimuon decay channel at low mass ($m_{\mu\mu}<$2~GeV/$c^{2}$) measured in A Large Ion Collider Experiment (ALICE). Only interacting electroweakly within the medium, the dimuon decay channel is considered as a clean probe and allows the reconstruction of various mesons among which the $\omega$ and the $\phi$ meson. Due to its $s\bar{s}$ content, the $\phi$ meson has the particularity of having strange content, but a null net strangeness content. For this reason, the $\phi$ meson is a particular probe to study the so-called strangeness enhancement, an effect proposed as a signature of the QGP. However, the $\omega$ meson is composed of light flavour quarks and can be used as a reference for a strange hadron production. Recently observed in small collision systems (such as pp), the strangeness enhancement is benefiting of a regain of interest. In this thesis the results on the $\omega$ and $\phi$ mesons production in pp collision at $\sqrt{s}~=~$5.02~TeV at forward rapidity with ALICE is presented. This thesis present the production of these mesons as a function of their transverse momentum, rapidity and multiplicity and the comparison to various model predictions.