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Higgs Boson Phenomenology Beyond the Standard Model Solen Le Corre

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Higgs Boson Phenomenology Beyond the Standard Model Solen Le Corre Higgs boson phenomenology beyond the Standard Model Solen Le Corre To cite this version: Solen Le Corre. Higgs boson phenomenology beyond the Standard Model. Nuclear Theory [nucl-th]. Université de Lyon, 2018. English. NNT : 2018LYSE1028. tel-01983201 HAL Id: tel-01983201 https://tel.archives-ouvertes.fr/tel-01983201 Submitted on 26 Oct 2020 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. No d’ordre NNT : 2018LYSE1028 THÈSEDEDOCTORATDEL’UNIVERSITÉDELYON opérée au sein de l’Université Claude Bernard Lyon 1 École Doctorale ED52 de Physique et d’Astrophysique Spécialité de doctorat : Physique Théorique / Physique des Particules Soutenue publiquement le 13 Mars 2018, par : Solen Le Corre Higgs boson phenomenology beyond the Standard Model Devant le jury composé de : Mme G. Bélanger Rapporteure M. G. Moreau Rapporteur Mme S. Gascon Shotkin Présidente du Jury Mme F. N. Mahmoudi Examinatrice M. A. Djouadi Examinateur M. U. Ellwanger Examinateur M. A. Deandrea Directeur de thèse M. A. Arbey Co-directeur de thèse Résumé Suite à la découverte du boson de Higgs en Juin 2012 au Large Hadron Collider, l’accélérateur de particules situé à la frontière franco-suisse, l’étude du secteur scalaire des particules élémen- taires a connu un regain d’intérêt. En particulier, le boson de Higgs étant une particule clef au sein du Modèle Standard des particules, les expérimentateurs étudient ses propriétés avec beaucoup de soin. Le Modèle Standard, dont le but est de décrire les interactions entre particules élémentaires, n’est cependant pas une théorie complète. En effet, en plus de quelques problèmes d’ordre théorique, certains phénomènes observés expérimentalement ne peuvent pas être expliqués par ce modèle. Les théoriciens en physique des particules cherchent donc à établir une nouvelle théorie venant le compléter et permettant d’expliquer pleinement les observations expérimen- tales. Ma thèse est axée sur l’étude du secteur scalaire de modèles au-delà du Modèle Standard des particules. J’ai plus particulièrement travaillé sur un modèle à deux doublets de Higgs – modèle purement effectif mais qui peut être inclus dans d’autres théories plus abouties – ainsi que sur un modèle construit comme une combinaison entre les théories déjà très proches de techicouleur et de Higgs composites, et ce dans le cas particulier d’une brisure de symétrie SU(4) → Sp(4). J’ai étudié ce dernier modèle d’un point de vue effectif mais la théorie complète est capable de pallier un certain nombre des limitations du Modèle Standard. Chacun de ces modèles inclut un secteur scalaire plus riche que celui du Modèle Standard et contient au moins une particule pouvant être assimilée au boson de Higgs découvert au LHC. J’ai réalisé l’étude phénoménologique de chacun de ces modèles et les ai confrontés à des contraintes tant théoriques qu’expérimentales – en particulier celles obtenues grâce aux études les plus récentes, portant sur le boson de Higgs et sur de potentielles particules scalaires ad- ditionnelles, réalisées par les équipes du LHC. Cela m’a permis de contraindre les paramètres libres des modèles et en particulier de restreindre les valeurs possibles pour la masse des autres particules scalaires, permettant de mieux cibler les zones où ces nouvelles particules, si elles existent, pourraient être détectées au LHC. Notons également que les deux théories sur lesquelles j’ai travaillé ne sont toujours pas exclues par les contraintes expérimentales les plus récentes. Mots clefs : Boson de Higgs, phénoménologie, LHC, scalaire, Higgs lourd, Higgs léger, Higgs chargé. III Summary Following the discovery of the Higgs boson in June 2012 at the Large Hadron Collider, the particle collider located beneath the France-Switzerland border, interest in the study of the scalar sector in elementary particle physics significantly increased. In particular, as the Higgs boson plays a very special role in the Standard Model of particle physics, experimentalists study its properties with great care. The goal of the Standard Model is to describe the interactions between elementary parti- cles. However the theory is not quite complete. Indeed, in addition to some purely theoretical problems, a number of experimental observations cannot be explained by the Standard Model. Theorists are therefore looking for a more comprehensive theory able to fully explain the ob- servations. This thesis is based on the study of the scalar sector of two different extensions of the Stan- dard Model of particle physics. I have worked on the Two-Higgs Doublet Model – this model is purely effective but can be included in more comprehensive theories – as well as on a model based on a combination of Technicolor and Composite Higgs theories in the framework of the SU(4) → Sp(4) symmetry breaking pattern. I studied the latter via an effective approach but the full theory is able to get rid of some of the pitfalls of the Standard Model. These two models include a scalar sector that is richer than the one found in the Standard Model and contain at least one particle which can be assimilated to the Higgs boson discovered at the LHC. I performed a phenomenological study for these two models and tested them against both theoretical and experimental constraints. In particular I used the latest studies on the 125 GeV Higgs boson and on possible additional scalars performed by the ATLAS and CMS collabora- tions. The application of all these constraints drastically reduced the available parameter space of the two models. In particular it narrowed the possible mass range of the additional scalars, allowing to know more accurately where to search them experimentally in order to prove or rule out their possible existence. As of today the two theories I worked on are still not excluded by the latest experimental data. Key words: Higgs boson, phenomenology, LHC, scalar particle, heavy Higgs, light Higgs, charged Higgs. V Remerciements J’aimerais remercier l’équipe de physique théorique de l’IPNL, tout d’abord Aldo Deandrea et Alexandre Arbey pour m’avoir accepté en thèse sous leur direction, Giacomo Cacciapaglia pour son aide discrète mais efficace durant ces trois années et Dany Davesne pour son humour défrisant et toute l’aide administrative qu’il m’a apportée. J’aimerais également remercier Suzanne Gascon et Morgan Lethuillier de l’équipe CMS pour m’avoir proposé un projet commun entre nos deux groupes qui m’a permis d’amorcer vérita- blement ma thèse. Je remercie également les autres doctorants sans qui ces trois années de thèse auraient été bien moins agréables : Pierre, Bertrand, Glenn, Lucille et les autres de l’équipe du midi, Eme- line pour les pauses thé trop vite avortées, ainsi qu’Anne-Laure, notamment pour son aide sur le déchiffrage de codes. Et, enfin et surtout, Nicolas qui, outre son humour particulier qui a bien souvent su me dérider, m’a tant de fois débloqué durant ma thèse grâce à ses explications lumineuses et ses références bibliographiques pertinentes que je ne saurais lui dire suffisamment merci. Je remercie également l’équipe enseignante avec qui j’ai travaillé durant ces trois ans : Houmani El Mamouni pour m’avoir, année après année, laissé la liberté de prendre plus de re- sponsabilités au sein de son UE, Floriane Poignant pour l’aide et la collaboration lors de notre toute première année d’enseignement, Sonia Fleck, d’une aide inestimable et qui abat un travail titanesque pour l’UE, Sylvain Monnier avec qui j’ai eu le plaisir de construire et développer les "mini-projets", ainsi que toute l’équipe du café pédagogique pour les discussions animées des vendredis après-midi. Un grand merci également à mon frère Julien qui a sacrifié ses vacances de Noël pour relire consciencieusement mon manuscrit et traquer les fautes d’anglais et les tournures de phrases trop "à la française". Je remercie également mes jury, en particulier mes rapporteurs Geneviève Bélanger et Gré- gory Moreau pour avoir accepté de lire et corriger mon manuscrit, et Suzanne Gascon pour avoir présidé le jury lors de ma soutenance. Je remercie enfin Romain, pour avoir été présent durant ces trois ans, et pour m’avoir soutenu, supporté et, surtout, attendu. VII Contents Introduction 1 I Introduction to particle and Higgs physics 3 1 The Standard Model of particle physics 5 1.1 Historical introduction ............................... 5 1.1.1 The beginning of particle physics ........................ 5 1.1.2Thephoton................................... 6 1.1.3 Antiparticles and the beginning of QED .................... 6 1.1.4Thecosmicrayturmoilandthedevelopmentofthequarkmodel...... 7 1.1.5 Beta decays and electroweak unification .................... 9 1.1.6Quarkmodel:theNovemberrevolution.................... 9 1.1.7 Final piece: the Higgs boson .......................... 10 1.2 Structure of the Standard Model ........................ 11 1.2.1Particlecontentandsymmetries........................ 11 1.2.2Lagrangianformulation............................. 13 1.3 The limitations of the Standard Model ..................... 26 2 The Higgs boson 31 2.1 History of the Higgs boson discovery ...................... 31 2.1.1 The beginning of the hunt – 1980s ....................... 31 2.1.2 The Large Electron Positron (LEP) – 1989-2000 ............... 32 2.1.3 The Tevatron – 1987-2011 ........................... 33 2.1.4 The Large Hadron Collider (LHC) – 2008-2035? ............... 33 2.2 Higgs boson production and decay at the LHC ................ 37 2.2.1ProductionattheLHC............................. 37 2.2.2SMHiggsbosondecays............................. 38 2.2.3 LHC results: signal strength and upper limits ................. 39 2.3 Consequences of LHC results on the 125 GeV Higgs boson .......
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