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It is generally well known that the Standard Model of particle physics is notthe ultimate theory of fundamental interactions as it has inumerous unsolvedproblems, so it must be extended. Deciphering the nature of dark matter remainsone of the great challenges of contemporary physics. Supersymmetry is probablythe most attractive extension of the SM. In the first part of this thesis westudy the interparticle potentials generated by the interactions betweenspin-1/2 sources that are mediated by spin-1 particles in the limit of lowmomentum transfer. We investigate different representations of spin-1 particleto see how it modifies the profiles of the interparticle potentials and we alsoinclude in our analysis all types of couplings between fermionic currents andthe mediator boson. The spin- and velocity-dependent interparticle potentialsthat we obtain can be used to explain effects possibly associated to newmacroscopic forces such as modifications of the inverse-square law and possiblespin-gravity coupling effects. The second part of this thesis is based on thedark matter phenomenology of well-motivated $U(1)'$ extensions of the MinimalSupersymmetric Standard Model. In these models the right-handed sneutrino is agood DM candidate whose dark matter properties are in agreement with thepresent relic density and current experimental limits on the DM-nucleonscattering cross section. In order to see how heavy can the RH sneutrino be asa viable thermal dark matter candidate we explore its DM properties in theparameter region that minimize its relic density via resonance effects and thusallows it to be a heavier DM particle. We found that the RH sneutrino canbehave as a good DM particle within minimal cosmology even with masses of theorder of tens of TeV, which is much above the masses that viable thermal DMcandidates usually have in most of dark matter particle models.

Search for new physics in light of interparticle potentials and a very heavy dark matter candidate