新粒子物理模型中的帶電輕子變味反應與雙希格斯粒子生成反應

Abstract

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In this thesis, I study several important topics in two different frontiers of particle physics. In the high intensity frontier, I study the charged lepton flavor violating radiative decays, muon-to-electron conversion in nuclei and electric dipole moments of electron and neutron in the electroweak-scale right-handed neutrino model proposed by Hung. The relevant parameters in the model are constrained by the latest limit from MEG for the radiative decay rate of muon into electron, the current experimental limits (SINDRUM II) and projected sensitivities (Mu2e, COMET and PRISM) for the muon-to-electron conversion rates in various nuclei and the latest limits for electron and neutron electric dipole moments from ACME experiment and ILL collaboration respectively. Overall, depending on the mirror fermion masses and mixing scenarios in the model, it turns out that the most stringent constraint is from the ACME experiment for the electron electric dipole moment which suggests the new Yukawa couplings of leptons should be minuscule of order $10^{-4}$ to $10^{-5}$, while the current limit on neutron electric dipole moment from ILL collaboration constrains the new Yukawa couplings of quarks to be of order $10^{-4}$. In the high energy frontier, I investigate the 125 GeV Higgs boson pair production at the Large Hadron Collider (LHC), which is a possible way to measure the trilinear Higgs self-coupling, in the new gauged two Higgs doublet model constructed recently by Huang, Tsai and Yuan. Both theoretical and experimental constraints on the parameter space of the model are taken into account. Theoretical constraints include the tree level vacuum stability and perturbative unitarity, while experimental constraints include the Higgs measurements at the LHC, PLANCK's relic density and direct search limits at XENON1T and PandaX-II of dark matter. I discuss impacts of these constraints on the total cross section of Higgs boson pair production in the model. I show that with additional contributions from the heavy scalar resonances as well as possible modifications in the 125 GeV Higgs self-coupling and extra self-couplings among different Higgses within the model, the total cross section of this process can be enhanced about one order of magnitude larger than the Standard Model prediction. Kinematic distributions of the two final states of $b\bar{b}\gamma\gamma$ and $b\bar{b}b\bar{b}$ at the LHC are also discussed.