Phenomenology of non-minimal supersymmetric models at linear colliders

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The focus of this thesis is on the phenomenology of several non-minimal supersymmetric models in the context of future linear colliders (LCs). Extensions of the minimal supersym- metric Standard Model (MSSM) may accommodate the observed Higgs boson mass at about 125 GeV in a more natural way than the MSSM, with a richer phenomenology. We con- sider both F -term extensions of the MSSM, as for instance the non-minimal supersymmetric Standard Model (NMSSM), as well as D -terms extensions arising at low energies from gauge extended supersymmetric models. The NMSSM oers a solution to the -problem with an additional gauge singlet supermultiplet. The enlarged neutralino sector of the NMSSM can be accurately studied at a LC and used to distinguish the model from the MSSM. We show that exploiting the power of the polarised beams of a LC can be used to reconstruct the neutralino and chargino sector and eventually distinguish the NMSSM even considering challenging sce- narios that resemble the MSSM. Non-decoupling D -terms extensions of the MSSM can raise the tree-level Higgs mass with respect to the MSSM. This is done through additional con- tributions to the Higgs quartic potential, eectively generated by an extended gauge group. We study how this can happen and we show how these additional non-decoupling D -terms aect the SM-like Higgs boson couplings to fermions and gauge bosons. We estimate how the deviations from the SM couplings can be spotted at the Large Hadron Collider (LHC) and at the International Linear Collider (ILC), showing how the ILC would be suitable for the model identication. Since our results prove that a linear collider is a fundamental machine for studying supersymmetry phenomenology at a high level of precision, we argue that also a thorough comprehension of the physics at the interaction point (IP) of a LC is needed. Therefore, we nally consider the possibility of observing intense electromagnetic eld eects and nonlinear quantum electrodynamics (QED) processes at the IP, due to the strong elec- tromagnetic elds generated by electron and positron bunches. We estimate the strength of the elds that would be generated at the planned LCs. We then argue that considering their eects on all physical processes may have strong impact on the ambitious precision physics program at the LC. We study how to test nonlinear QED colliding an intense laser on the beams of a LC, in an eort to improve and extend the success of SLAC experiment 144.