. "\u00C9tude de la d\u00E9pendance en multiplicit\u00E9 de particules charg\u00E9es de la production de J/ \u03A8 dans les collisions p-Pb \u00E0 \u221AsNN = 5.02 TeV et les collisions pp \u00E0 \u221AsNN = 8 TeV avec l\u2019exp\u00E9rience ALICE au LHC" . . . . "Collisions p\u2013Pb" . "Study of J/\u03A8 production dependence with the charged particle multiplicity in p-Pb collisions at \u221AsNN = 5.02 TeV and pp collisions at \u221As = 8 TeV with the ALICE experiment at the LHC " . "Study of J/\u03A8 production dependence with the charged particle multiplicity in p-Pb collisions at \u221AsNN = 5.02 TeV and pp collisions at \u221As = 8 TeV with the ALICE experiment at the LHC " . . . "J/\u03C8" . "Mati\u00E8re nucl\u00E9aire" . "Plasma quark-gluon" . . . "Exp\u00E9rience ALICE" . "A suppression of the J/\u03A8 production was found in Pb- Pb collisions at \u221AsNN = 2.76 TeV, providing further evidence of the formation of a deconfined medium in ultrarelativistic heavy-ion collisions, the so-called Quark- Gluon Plasma. In addition, p-Pb collisions at \u221AsNN = 5.02 TeV have been studied at the LHC to measure cold nuclear matter effects (e.g. gluon shadowing, energy loss, nuclear absorption). Understanding p-Pb collisions will help to disentangle hot and cold nuclear matter effects in Pb-Pb collisions. Surprisingly, some observables in p-Pb collisions behave as in heavy-ion collisions where it is understood as a result of a collective expansion of the medium. This thesis analyses inclusive J/\u03A8 production in p- Pb and pp collisions with the ALICE muon spectrometer. The J/\u03A8 production rate, and its mean transverse momentum, have been measured at forward and backward rapidities as a function of the charged particle multiplicity. Measurements of particle production as a function of the event multiplicity in small size systems provide a way to sign the presence of collective final state effects like those observed in Pb-Pb collisions. The observed increase of the J/\u03A8 production at backward rapidity with multiplicity, is consistent with that observed in pp collisions. However, a deviation from this behaviour in the J/\u03A8 production at forward rapidity at high multiplicity has been measured. A trend towards saturation has also been observed in the J/\u03A8 mean transverse momentum in p-Pb collisions. Whether these effects can be explained by cold nuclear matter effects or by the presence of further final state effects is still unresolved." . "Une suppression de la production de J/ \u03A8 a \u00E9t\u00E9 mise en \u00E9vidence lors des collisions Pb-Pb \u00E0 \u221AsNN = 2.76 TeV, fournissant une preuve suppl\u00E9mentaire de la formation d\u2019un milieu d\u00E9confin\u00E9 au cours des collisions d\u2019ions lourds ultra-relativistes, appel\u00E9 Plasma de Quarks et Gluons. Par ailleurs, les collisions p-Pb \u00E0 \u221AsNN = 5.02 TeV ont \u00E9t\u00E9 \u00E9tudi\u00E9es au LHC afin de mesurer les effets de la mati\u00E8re nucl\u00E9aire froide (p. ex. \u00E9crantage des gluons, perte d\u2019\u00E9nergie, absorption nucl\u00E9aire). La compr\u00E9hension des collisions p-Pb aidera \u00E0 dissocier les effets de la mati\u00E8re nucl\u00E9aire chaude et froide dans des collisions Pb-Pb. Cette th\u00E8se analyse la production inclusive de J/ \u03A8 dans les collisions p-Pb et pp avec le spectrom\u00E8tre \u00E0 muons de l\u2019experience ALICE. Le taux de production de J/ \u03A8 et son moment transverse moyen, ont \u00E9t\u00E9 mesur\u00E9s pour des rapidit\u00E9s \u00E0 l\u2019avant et \u00E0 l\u2019arri\u00E8re en fonction de la multiplicit\u00E9 des particules charg\u00E9es. Des mesures de la production de particules en fonction de la multiplicit\u00E9 de l\u2019\u00E9v\u00E9nement dans des syst\u00E8mes de petite taille permettent de mettre en \u00E9vidence des effets collectifs de l\u2019\u00E9tat final, comme ceux observ\u00E9s dans les collisions Pb-Pb. L\u2019augmentation observ\u00E9e, avec la multiplicit\u00E9, de la production de J/ \u03A8 aux rapidit\u00E9s \u00E0 l\u2019arri\u00E8re, est en accord avec celle mise en \u00E9vidence en collisions pp. Cependant, une d\u00E9viation de ce comportement pour la production de J/ \u03A8 aux rapidit\u00E9s \u00E0 l\u2019avant \u00E0 haute multiplicit\u00E9 \u00E0 \u00E9t\u00E9 mesur\u00E9e. Une tendance \u00E0 la saturation du moment transverse moyen du J/ \u03A8 en collisions p-Pb a aussi \u00E9t\u00E9 observ\u00E9e. L\u2019origine de ces comportements, qu\u2019ils soient li\u00E9s aux effets de la mati\u00E8re nucl\u00E9aire froide ou \u00E0 la pr\u00E9sence d\u2019autres effets dans l\u2019\u00E9tat final, n\u2019est toujours pas connue." . . . . . "2015" . . . "Th\u00E8ses et \u00E9crits acad\u00E9miques" . . . . "Grand collisionneur de hadrons" . "Text" . . . .