Sophie L. Williamson

Phénoménologie et contraintes de collisionneur des modéles supersymétriques à l'ére run 2 du LHC: Il a longtemps été pensé que le modèle standard (MS) est une description incomplète de notre univers, mais les résultats expérimentaux obtenus jusqu'à présent ne confirment rien de plus. La supersymétrie minimale, concrétisée par le modèle standard supersymétrique minimal (MSSM), est une extension compétitive du MS et a été bien étudiée, en particulier dans le contexte de modèles simplifiés, au niveau des collisionneurs. Cependant, les techniques de recherche actuelles n'utilisent peut-être pas de manière optimale la capacité du collisionneur à tester l'espace de paramètre accessible. Au lieu d'utiliser un veto statique sur le momentum du jet pour minimiser les processus d'arrière-plan indésirables dans les recherches de signaux, il peut être démontré que l'utilisation d'un veto au jet dynamique construit à partir de plusieurs mesures d'activité hadronique et leptonique peut augmenter le potentiel de découverte des balayages MSSM simplifiés. Dans le même temps, il est indéniable que les limites imposées aux modèles simplifiés ne représentent pas fidèlement des scénarios plus complexes - en particulier les modèles de supersymétrie non minimaux dans lesquels les signatures de désintégration sont modifiées par un spectre plus complexe de chargino et de neutralino. Les gauginos de Dirac (DG) constituent une extension non minimale bien motivée qui semble plus plausible que le MSSM, qui est de plus en plus constraint par les observations. Ce travail peut être divisé en deux parties: (1) il étudie comment le contenu en particules élargi des modèles DG peut modifier les limites actuelles de la masse de gluino et de squark du Run 2 du LHC, et (2) effectue une étude approfondie du secteur de Higgs dans de tels modèles, qui est automatiquement aligné en raison de la supersymétrie étendue qui relie les couplages de Yukawa aux couplages de jauge dans le secteur électrofaible.

Supersymmetric models with Dirac instead of Majorana gaugino masses have distinct phenomenological consequences. In this paper, we investigate the electroweakino sector of the Minimal Dirac Gaugino Supersymmetric Standard Model (MDGSSM) with regards to dark matter (DM) and collider constraints. We delineate the parameter space where the lightest neutralino of the MDGSSM is a viable DM candidate, that makes for at least part of the observed relic abundance while evading constraints from DM direct detection, LEP and low-energy data, and LHC Higgs measurements. The collider phenomenology of the thus emerging scenarios is characterised by the richer electroweakino spectrum as compared to the Minimal Supersymmetric Standard Model (MSSM) -6 neutralinos and 3 charginos instead of 4 and 2 in the MSSM, naturally small mass splittings, and the frequent presence of long-lived particles, both charginos and/or neutralinos. Reinterpreting ATLAS and CMS analyses with the help of SmodelS and MadAnalysis 5, we discuss the sensitivity of existing LHC searches for new physics to these scenarios and show which cases can be constrained and which escape detection. Finally, we propose a set of benchmark points which can be useful for further studies, designing dedicated experimental analyses and/or investigating the potential of future experiments.

Supersymmetric models with Dirac instead of Majorana gaugino masses have distinct phenomenological consequences. In this paper, we investigate the electroweakino sector of the Minimal Dirac Gaugino Supersymmetric Standard Model (MDGSSM) with regards to dark matter (DM) and collider constraints. We delineate the parameter space where the lightest neutralino of the MDGSSM is a viable DM candidate, that makes for at least part of the observed relic abundance while evading constraints from DM direct detection, LEP and lowenergy data, and LHC Higgs measurements. The collider phenomenology of the thus emerging scenarios is characterised by the richer electroweakino spectrum as compared to the Minimal Supersymmetric Standard Model (MSSM) -- 6 neutralinos and 3 charginos instead of 4 and 2 in the MSSM, naturally small mass splittings, and the frequent presence of long-lived particles, both charginos and/or neutralinos. Reinterpreting ATLAS and CMS analyses with the help of SModelS and MadAnalysis 5, we discuss the sensitivity of existing LHC searches for new physics to these scenarios and show which cases can be constrained and which escape detection. Finally, we propose a set of benchmark points which can be useful for further studies, designing dedicated experimental analyses and/or investigating the potential of future experiments.

Most SUSY searches at the LHC are optimised for the MSSM, where gauginos are Majorana particles. By introducing Dirac gauginos, we obtain an enriched phenomenology, from which considerable differences in the LHC signatures and limits are expected as compared to the MSSM. Concretely, in the minimal Dirac gaugino model (MDGSSM) we have six neutralino and three chargino states. Moreover, production cross sections are enhanced for gluinos, while for squarks they are suppressed. In this contribution, we explore the consequences of the current LHC limits on gluinos and squarks in this model.

Most SUSY searches at the LHC are optimised for the MSSM, where gauginos are Majorana particles. By introducing Dirac gauginos, we obtain an enriched phenomenology, from which considerable differences in the LHC signatures and limits are expected as compared to the MSSM. Concretely, in the minimal Dirac gaugino model (MDGSSM) we have six neutralino and three chargino states. Moreover, production cross sections are enhanced for gluinos, while for squarks they are suppressed. In this contribution, we explore the consequences of the current LHC limits on gluinos and squarks in this model.

Multilepton searches for electroweakino and slepton pair production at hadron colliders remain some of the best means to test weak-scale supersymmetry. Searches at the CERN Large Hadron Collider, however, are limited by large diboson and top quark pair backgrounds, despite the application of traditional, central jet vetoes. In this context, we report the impact of introducing dynamic jet vetoes in searches for colorless superpartners. As a representative scenario, we consider the Drell-Yan production of a pair of right-handed smuons decaying into a dimuon system accompanied with missing transverse energy. As an exploratory step, we consider several global and local measures of the leptonic and hadronic activity to construct the veto. In most all cases, we find that employing a dynamic jet veto improves the sensitivity, independently of the integrated luminosity. The inclusion of non-perturbative multiple particle interactions and next-to-leading order jet merging does not alter this picture. Directions for further improvements are discussed.

Multilepton searches for electroweakino and slepton pair production at hadron colliders remain some of the best means to test weak-scale supersymmetry. Searches at the CERN Large Hadron Collider, however, are limited by large diboson and top quark pair backgrounds, despite the application of traditional, central jet vetoes. In this context, we report the impact of introducing dynamic jet vetoes in searches for colorless superpartners. As a representative scenario, we consider the Drell-Yan production of a pair of right-handed smuons decaying into a dimuon system accompanied with missing transverse energy. As an exploratory step, we consider several global and local measures of the leptonic and hadronic activity to construct the veto. In most all cases, we find that employing a dynamic jet veto improves the sensitivity, independently of the integrated luminosity. The inclusion of nonperturbative multiple particle interactions and next-to-leading order jet merging does not alter this picture. Directions for further improvements are discussed.

We consider the effective type-II Two-Higgs doublet model originating from Dirac gaugino models with extended supersymmetry in the gauge sector, which is automatically aligned in the simplest realisations. We show that raising the scale at which the extended supersymmetry is manifest and including quantum corrections actually improves the alignment. Using an effective field theory approach including new threshold corrections and two-loop RGEs, plus two-loop corrections to the Higgs mass in the low-energy theory, we study the implications from the Higgs mass and other experimental constraints on the scale of superpartners. We contrast the results of the minimal Dirac gaugino model, where alignment is automatic, with the hMSSM and the MRSSM, where it is not, also providing an hMSSM-inspired analysis for the new models.