由五維Split Fermion模型及Zee模型探討微中子質量

Neutrino Masses Through Zee Mechanism in 5D Split Fermion Model

陳依婷

指導教授 ： 張維甫

國立清華大學/理學院/物理學系/碩士(2009年)

https://doi.org/10.6843/NTHU.2009.00448

摘要

微中子震盪是一個有趣且重要的現象，它代表微中子帶有質量，並因為其弱作用力本徵態與質量本徵態並不一致， 所以微中子在運動過程中，會在不同弱作用力本徵態之間互相震盪。標準模型無法解釋此一現象，所以我們需要新的物理模型。
為了解釋微中子質量來源，我們引進 Zee 模型以及額外空間。首先，我們假設除了原本的四維空間中，還存在一個額外的第五維度，然後計算五維空間中的 Zee 模型，得到產生微中子的Majorana 質量型式。接下來，利用Split Fermion 模型，將費米子固定在此五維空間的一個四維膜上，而希格斯玻色子則可以在第五維空間中自由傳遞，再由此計算出微中子質量型式當中的一些參數型式。接著利用轉換矩陣 PMNS 矩陣，最後我們可以
計算帶電輕子的質量，微中子的質量本徵值以及混合角度等等的分布範圍。根據人擇原理，將上面所算的結果跟相關實驗值比較，我們得到四組可以包含實驗數據的結果。最後我們再計算五個輕子數不守恆衰變過程的branch ratio，結果也符合實驗限制。所以推測這是個可能的模型。

關鍵字

微中子震盪 ； 額外空間

並列摘要

The phenomenon of neutrino oscillation implies that neutrinos have masses, and the flavor eigenbasis is not the mass eigenbasis, so neutrinos oscillate between different flavor states while traveling. Thus it is beyond the Standard Model, and it calls for new physics.Here we
study the Zee model and Extra dimensions to explain the neutrino oscillation. First, suppose there exists a compactied fth dimension, and neutrinos have Ma jorana masses through the 5 dimensional Zee model. Second, assume the fermions are localized on a 4 dimensional brane embedded in the 5 dimensional space-time by the Split Fermion model, while the higgs are free to propagate along the extra dimension. We can get the forms of parameters in the neutrino mass matrix from Zee model. Then, transforming with the PMNS matrix, we found ranges of charged lepton masses, neutrino masses and mixing angles, and so on. Based on Anthropic Principle, we compare them to the experiment data, and we get 4 possible solutions. We also check the branch ratios of 5 lepton flavor violating processes, and they also satisfy the experiment constraints. Thus this is a possible model.

並列關鍵字

Neutrino oscillation ； Zee Model ； Extra dimensions ； Split fermion Model ； PMNS matrix ； Anthropic Principle

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