http://swrc.ontoware.org/ontology#Thesis
Physics Beyond the Standard Model and Dark Matter
en
浅野 雅樹
アサノ マサキ
ASANO Masaki
総研大甲第1142号
Although the standard model of the elementary particle physics has been successful for the last thirty years, several problems have been pointed out. Among them, the hierarchy problem and the existence of the dark matter especially lead us to consider new physics at the TeV scale. In this thesis, I investigate the supersymmetric model and the little Higgs model from these viewpoints. These models are possible simultaneous solutions to these two problems. <br /> In the little Higgs model, we focus on the littlest Higgs model with T-parity which is one of the simplest models implementing the little Higgs mechanism. T-parity is $Z_2$ symmetry which guarantees the stability of the lightest T-odd particle. The heavy photon is a dark matter candidate in this model. The dark matter mainly decays into weak gauge bosons in the galactic halo through s-channel annihilation, and therefore high energy positrons are produced by these bosons decays. We investigate a possibility of the dark matter detection using cosmic positrons in future experiments such as PAMERA and AMS-02. We calculate the expected positron flux at the Earth. We have found that the dark matter signal can be distinguished from backgrounds in the AMS-02, while the possibility of dark matter detection in PAMERA depends on model parameters. We also consider constraints from electroweak precision measurements. We recalculate contributions to Peskin and Takeuchi S, T, U parameters from heavy gauge boson loops. We also discuss the invisible decay width of the Higgs boson.<br /> In the supersymmetric model, we focus on the light Higgs boson scenario in which the mass of the lightest Higgs boson is less than 114.4 GeV. Although such a small mass is excluded by LEP2 experiments in the standard model, this region can be still allowed in the supersymmetric model. In this thesis, we determine model-parameters in the non-universal Higgs mass model, where universality relations on soft supersymmetry breaking mass terms are relaxed for the Higgs super multiplets in the mSUGRA model. We show that the scenario is consistent not only with results of many collider experiments but also with the observed relic abundance of dark matter. We also discuss the impact of dark matter search experiments for this scenario.