Physique du LHC et extensions du modèle standard.

Abstract

Though very successful at describing a wide variety of particle physics phenomenons, the standard model leaves some proprieties of nature unexplained. This fact lead physicists to search for new solutions based on extended symmetries or extra degree of freedoms. In this thesis we focus on two of the new physics proposal, the unparticle model and the left right symmetric model. We begin by presenting the theoretical framework upon which unparticle are founded, conformal field theory. Then, we describe briefly the original formulation of the unparticle model by Georgi and subsequent works relevant to our study. Next, we construct a gauged unparticle model charged under the standard model electroweak group SU(2)×U(1). Any new physics model must be compatible with the standard model predictions. In this regard the electroweak precision tests represent a powerful tool to check the compatibility of new physics model with experimental data. For the gauged unparticle model we calculate the oblique parameters S and T that parametrize the contribution of new physics states to electroweak observables. We then use the bound for these parameters extracted from LEP and other experiments to constrain the parameters space of unparticles. Finally, we consider the effects of left right symmetric model spectrum on the muon anomalous magnetic moment and use it to decrease the deviation between the SM predictions and experimental observations . A paper describing part of the results of this dissertation has been published in the Journal Modern Physics Letters A, entitled: ”Constraints on electroweak gauged unparticle model from the oblique parameters S and T”