Anomalous U(1), Dark Matter and Asymmetry

Abstract

In this thesis we study the phenomenology of an anomalous U(1) extension of the MSSM. We briefly introduce the concept of Supersymmetry and describe the MSSM, then we introduce our extended model, describing its main properties. Then it starts the original part of the thesis. First there is the study of the model in the most general case, in which there is mixing between the SM U(1) and the anomalous U(1). This is followed by the calculation of all the vertices and the amplitudes that are of interest for the phenomenology that we are going to study. After describing in details how the Boltzmann Equation gives the relic density of particle species, we use it and the amplitudes of our model already calculated to study if the neutralinos introduced by our model can be viable candidates to describe the Dark Matter relic density. We have found that this is the case only if the anomalous candidate coannihilates with a MSSM neutralino. In the case of no mixing between the U(1)s we have obtained this results performing analytical calculations, whom results we show for many mass gaps. To obtain the same result in the mixing case we have modified the DarkSUSY package. This has also permitted us to obtain more precise informations about the dependence of the relic density on the various free parameters of the model. We show many plots containing these results. In the last part of the thesis we study the Asymmetry at the LHC for our model. We start introducing the Forward-Backward Asymmetry then we move on to describe how it can be utilized at the LHC. We introduce different possible definitions and describe their properties, then we calculate their predicted values in our model. Finally we explain how these results could be used to impose constraints over theoretical models that describe beyond the Standard Model physics.