FlorianNortier Statut : Doctorant Fonction : Groupe de Physique des Particules Tel. 33 (0) 1 69 15 63 53 Fax. 33 (0) 1 69 15 82 87 Adresse : bat. 210 - bureau 108D Mél. : Florian.Nortier -At- th.u-psud.fr

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Recherche Domaine : Physique des 2 Infinis (P2I) Mots clés : flat/warped extra dimensions (bulk, p-branes, compactification, radion/dilaton, KK-particles), Kaluza-Klein and Randall-Sundrum models, electroweak Higgs sector. Sujet de thèse : Origins of Electroweak Symmetry Breaking: The Higgs Field in Scenarii with Extra Spatial Dimensions (PhD advisor: Grégory MOREAU).

Thèmes
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In the Standard Model (SM) of Particle Physics, the electroweak (EW) symmetry breaking pattern is the less known and understood. With the discovery of a Higgs-like boson by the Large Hadron Collider (LHC) experiment in 2012, the Brout-Englert-Higgs (BEH) mechanism, which involves a new scalar field to break the EW gauge symmetry, seems to be at work in Nature. Nevertheless, the origin of the BEH field remains a mystery and it suffers from a technical naturalness puzzle: why the Higgs boson is so light compared to the quantum gravity scale? The Higgs sector can also play an important role to understand the open questions of the SM, like the flavour landscape, the masses of the neutrinos, the dark components of the Universe, the inflation... My PhD subject involves studying models with spatial extra dimensions, which could solve some of these questions. Several scenarii are present in the literature: brane worlds, warped and/or magnetized extra dimensions, Gauge-Higgs Unification (GHU). In practice, I develop models using some of these frameworks, from which I dig out the first phenomenological consequences.

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In Randall-Sundrum 1 (RS1) models, one supposes the existence of a fifth spatial dimension, compactified on a 1D orbifold: the line segment. This extra dimension (ED) is warped and bounded by two 3-brane: a UV-brane, where the quantum gravity scale is huge (of the same order than the usual 4D one) and an IR-brane with a TeV one. This strange phenomenom is due to the curvature along the ED. Therefore, confining the Brout-Englert-Higgs (BEH) field on the IR-brane solves the naturalness puzzle of the Standard Model (SM). Moreover, the fermionic and gauge fields of the SM model can propagate in the ED, where the different lepton and quark flavor profiles can be localized at different places. The effective 4D Yukawa couplings of the SM are proportional to the values of the field profiles on the IR-brane (overlap with the BEH field). As a consequence, the flavor hierarchy puzzle of the SM can be explained by a localization pattern of the fermions in the ED. This is thus important to realize an update of the constrains on the RS1 scenarii with the new datas of the Large Hadron Collider (LHC).