在原子核中，中子及質子會形成束縛態使得原子核穩定。而在原子核中，中子幾乎是穩定態。不過當中子在原子核外時（稱為自由中子），將會變得非常不穩定，並且透過理論計算自由中子的壽命大約為881.5±1.5 s。有了理論計算的結果，實驗量測也應該會有相似結果。但是事實卻不是如此。在多年前，美國團隊及法國團隊分別以 « Beam experiment »和 « Bottle experiment »量測中子的壽命。但是實驗結果明顯的有差異，起初物理學家覺得可能是某一組的實驗團隊有錯誤，才造成此誤差。近幾年，美國研究團隊進行了一項長期且嚴謹的實驗來探討之前的實驗中所有的誤差來源，最後反而是更確定了兩個實驗結果的差異性。
  至今為止中子的壽命依舊是個謎團。許多理論物理學家開始建立暗物質模型並且解釋中子衰變異常。而此研究報告也是建立一個暗物質模型來解釋中子衰變異常，此模型也可以透過暗物質及新的純量場計算出微中子質量。

Inside the nucleus, there are protons and neutrons and they form the bound states. When neutron leave the nucleus, it will become an unstable particle which is called a free neutron. The free neutron lifetime is predicted to be 881.5±1.5 s by the Standard Model. For years the experimental measurement are basically consistent with the theoretical results. However, recently laboratories in USA (Beam experiment) and France (Bottle experiment) were shown that the neutron lifetime anomaly, namely a discrepancy of about 1% is found between the experimental measurements and the theoretical prediction. 
  Regarding the neutron lifetime anomaly. We propose an new gauge U(1) symmetry portal to  dark matter to resolve the neutron lifetime anomaly. The symmetry breaking pattern of this new gauge symmetry will also shed light on the neutrino mass generation through the quantum radioactive corrections.

Contents:
1 Introduction...1
2 Standard Model(SM)...3
 2.1 Spontaneous symmetry breaking...7
 2.2 Standard electroweak theory...8
  2.2.1 Gauge fi elds...8
  2.2.2 Fermions...9
  2.2.3 Symmetry breaking via the Higgs mechanism...10
  2.2.4 Mass spectrum...11
  2.2.5 Charge current and Neutral currents...12
 2.3 Neutrino mass problem and dark matter...13
3 Neutron lifetime anomaly...15
 3.1 Introduction...15
 3.2 Neutron Lifetime with Theoretical description...16
 3.3 Experiment of Neutron lifetime...17
  3.3.1 Bean experiment...18
  3.3.2 Bottle experiment...18
  3.3.3 Result of neutron lifetime...19
4 Dark Matter...24
 4.1 Background...24
 4.2 Observational evidences...25
  4.2.1 Galaxy rotation curve...25
  4.2.2 Gravitational lensing...26
  4.2.3 Collision of two galaxies...27
 4.3 Dark matter theory and initial conditions...28
 4.4 Small scale structure problem...29
  4.4.1 The core-cuspy problem...29
  4.4.2 The missing satellites problem and 
        the too-big-to-fail problem...30
 4.5 Self-Interacting Dark Matter...31
5 Neutrino...33
 5.1 Introduction...33
 5.2 Seesaw Mechanism...36
  5.2.1 Radiative Seesaw Mechanism...38
6 The frame of model...41
 6.1 Research motivation...41
 6.2 Gauge group...41
 6.3 The radiative neutrino mass model...43
 6.4 Conclusion...47

List of Figures:
3.1 Bean experiment...18
3.2 Bottle experiment...19
3.3 The history of the neutron lifetime...20
4.1 Rotation Curve of the M33 galaxy...26
4.2 Gravitational lensing...27
4.3 Bullet Cluster...28
4.4 The Virgo cluster and simulated of the cluster...30
4.5 The circular velocity pro les for MW subhalos 
    by simulation...31
5.1 The one-loop neutrino mass model,credited by [1]...39
6.1 The one loop model of neutrino...43
6.2 The numerical results of my neutrino mass model...46

List of Tables:
2.1 Three generations fermions...3
2.2 Twelve gauge bosons and Higgs boson...4
2.3 The quantum number of leptons...5
2.4 The quantum number of quarks...5
2.5 The quantum number of mediator...6
2.6 The quantum number on SU(2)L*U(1)Y gauge...9
5.1 The particles under SU(2)L*U(1)Y*Z2 group...39
6.1 The quantum number on SU(2)L*U(1)Y*U(1)' gauge...44

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