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Ultimo aggiornamento 19 gen 2018
Autore
Giulia Rovelli
Sesso F
Esperimento ATLAS
Tipo Laurea Magistrale
Destinazione dopo il cons. del titolo Dottorato (Italia)
Università Universita' Di Pavia
Strutt.INFN/Ente
Pavia
Titolo Search for Dark Matter production at accelerators
Abstract The Standard Model (SM) of high-energy physics provides a remarkably successful description of presently known phenomena. However, while the SM provides a theoretically consistent description of all known particles and their interactions (ignoring gravity) up to the Planck scale, it is clearly incomplete, as it does not address several pieces of evidence for new physics beyond the SM. A pragmatic approach to expand the SM is to consider the strongest piece of evidence of physics beyond the SM: the existence of Dark Matter (DM), coming from cosmological studies. Its existence provides a strong hint that there may be a dark sector, consisting of particles that do not interact with the known strong, weak, or electromagnetic forces. These dark sectors (or “hidden sectors”) may contain new light weakly-coupled particles, particles well below the TeV-scale that interact only feebly with ordinary matter. Such particles could easily have escaped past experimental searches, but a rich experimental program has now been devised to look for several well-motivated possibilities. Besides gravity, there are only a few well-motivated interactions allowed by SM symmetries that provide a “portal” from the SM sector into the dark sector. One of the simplest possible realization is by employing a vector gauge field, the so-called Dark Photon A’ (DP), which interacts weakly with the SM fermions. The Dark Photon kinetically mix with the SM photon with a mixing strength ε ≪ 1, and can then appear in every process involving photons at accelerators. Another way to account for the existence of DM in an easy way is to suppose that the dark sector consists only of one neutral particle, which interact with SM particles through a mediator. This hypothesis characterizes simplified models, on which are based most of the present searches being performed at LHC. However, these models introduce a mixing between the mediator and the SM bosons, severely excluded by LEP and LHC measurements. To overcome this problem, more complete models have been developed, with the introduction of more particles. In particular, one of the most popular model studied nowadays is the Two Higgs Doublets Model + Pseudoscalar Mediator (2HDMp). This model introduces in the SM, in addition to a pseudoscalar singlet mediator and a neutral particle, another Higgs doublet, which prevents the mediator from mixing with the SM Higgs. The mediator and the adjoint Higgs doublet mix, giving rise to six new bosons, either scalar, pseudoscalar or charged. Thus the model experimental signatures are very various, usually involving missing energy along with SM particles. The aim of this thesis is to address the search for DM production at accelerator in these theoretical frameworks. In the first part, the problem of the search for Dark Photon at the NA62 experiment is addressed, while in the second part the 2HDMp model is analyzed within the ATLAS experiment. Both studies have shown promising results, highlighting all the potential of accelerator searches for DM.
Anno iscrizione 2015
Data conseguimento 27 ott 2017
Luogo conseguimento Pavia
Relatore/i
Giacomo Polesello   
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