微中子和暗物質的離散規範對稱模型

Model for neutrino masses and dark matter with a discrete gauge symmetry

黃志峰(Chi-Fong Wong)

指導教授 ： 張維甫

國立清華大學/理學院/物理學系/博士(2014年)

https://doi.org/10.6843/NTHU.2014.00391

摘要

A novel renormalizable extension of Standard Model with a discrete gauge Z2 symmetry is intro- duced. In this model, tiny neutrino masses are obtained at one-loop level; moreover, the new scalar bosons involved in the loop corrections play a role as stable cold dark matter candidates. The absence of tree-level neutrino masses and stability of dark matter candidates are guaranteed by the discrete gauge Z2 symmetry. The Z2 symmetry is the unbroken subgroup of a spontaneously broken gauge U1ν symmetry by means of Krauss-Wilczek mechanism. The energy scale of U1ν breaking is assumed at around TeV scale, therefore, new degrees of freedom in this model are promising to test in colliders such as LHC at CERN. In this proposal, only Lorentz symmetry, gauge symmetry and renormaliz- ability are considered in model construction, hence it is different with other similar proposals wherein global symmetry is put by hand.
In this thesis, we start with a brief review on neutrino properties in Standard Model, followed by formalism on neutrino oscillations, and oscillation experiments, neutrino mass measurements, and a summary on the latest results. Seesaw mechanism and its realizations will be reviewed. Next, We review evidence of dark matter followed by its inferential properties. Two existing models: Krauss- Nasri-Trodden model and Ma model are reviewed, from which we can have a taste on how Z2 parity connects topics of radiative neutrino masses and stable dark matter together. After that, we start to explain our motivation in detailed and introduce the gauge group, particle content and hence La- grangian of our model. Accordingly, radiative neutrino masses are calculated, and parameters in the model are estimated. Therefore we predict the Lepton Flavour Violating decays li → lj γ in this model. Moreover, to identify the cold dark matter candidate, the dominated reaction for thermal equilibrium in early universe is calculated, therefore we conclude that the new CP even scalar boson or the new CP odd scalar boson in this model are the viable dark matter candidates. The mass range is also discussed.

關鍵字

neutrino ； dark matter ； Krauss-Wilczek Mechanism

並列摘要

A novel renormalizable extension of Standard Model with a discrete gauge Z2 symmetry is intro- duced. In this model, tiny neutrino masses are obtained at one-loop level; moreover, the new scalar bosons involved in the loop corrections play a role as stable cold dark matter candidates. The absence of tree-level neutrino masses and stability of dark matter candidates are guaranteed by the discrete gauge Z2 symmetry. The Z2 symmetry is the unbroken subgroup of a spontaneously broken gauge U1ν symmetry by means of Krauss-Wilczek mechanism. The energy scale of U1ν breaking is assumed at around TeV scale, therefore, new degrees of freedom in this model are promising to test in colliders such as LHC at CERN. In this proposal, only Lorentz symmetry, gauge symmetry and renormaliz- ability are considered in model construction, hence it is different with other similar proposals wherein global symmetry is put by hand.
In this thesis, we start with a brief review on neutrino properties in Standard Model, followed by formalism on neutrino oscillations, and oscillation experiments, neutrino mass measurements, and a summary on the latest results. Seesaw mechanism and its realizations will be reviewed. Next, We review evidence of dark matter followed by its inferential properties. Two existing models: Krauss- Nasri-Trodden model and Ma model are reviewed, from which we can have a taste on how Z2 parity connects topics of radiative neutrino masses and stable dark matter together. After that, we start to explain our motivation in detailed and introduce the gauge group, particle content and hence La- grangian of our model. Accordingly, radiative neutrino masses are calculated, and parameters in the model are estimated. Therefore we predict the Lepton Flavour Violating decays li → lj γ in this model. Moreover, to identify the cold dark matter candidate, the dominated reaction for thermal equilibrium in early universe is calculated, therefore we conclude that the new CP even scalar boson or the new CP odd scalar boson in this model are the viable dark matter candidates. The mass range is also discussed.

參考文獻

As shown in fulltext.