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arXiv 1504.06291hep-phhep-th
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经典共形U(1)$^\prime$扩展标准模型与Higgs真空稳定性

Classically conformal U(1)$^\prime$ extended Standard Model and Higgs vacuum stability

Satsuki Oda, Nobuchika Okada, Dai-suke Takahashi

摘要:

考虑了经典水平上具有共形不变性的标准模型的最小U(1)$^\prime$扩展,其中除了引入SM粒子外,还引入了三代右手中微子和一个U(1)$^\prime$ Higgs场.在三个右手中微子的存在下,这是负责跷跷板机制,这个模型是免费的所有规范和引力异常。U(1)$^\prime$规范对称性通过Coleman-Weinberg机制辐射破缺,由此产生U(1)$^\prime$规范玻色子($Z^\prime$ boson)质量以及右手中微子的Majorana质量。辐射U(1)$^\prime$对称性破缺也导致SM Higgs二重态产生负质量平方,从而触发电弱对称性破缺。在这种情况下,我们调查的可能性,以解决SM希格斯真空不稳定性问题。该模型只包含三个自由参数(SM Higgs二重态的U(1)$^\prime$荷、U(1)$^\prime$规范耦合和$Z^\prime$玻色子质量),我们对它们进行了参数扫描,确定了一个解决SM Higgs真空不稳定性的参数区域.我们还研究了模型的自然性。与U(1)$^\prime$对称性破缺相关的重态对SM Higgs自能有贡献。我们发现了$Z^\prime$玻色子质量的上限,$m_{Z^\prime} \lesssim 6$ TeV,以避免微调超过10%的水平。这个质量范围内的$Z^\prime$玻色子可以在不久的将来在LHC Run-2中发现。

英文摘要:

We consider the minimal U(1)$^\prime$ extension of the Standard Model (SM) with conformal invariance at the classical level, where in addition to the SM particle contents, three generations of right-handed neutrinos and a U(1)$^\prime$ Higgs field are introduced. In the presence of the three right-handed neutrinos, which are responsible for the seesaw mechanism, this model is free from all the gauge and gravitational anomalies. The U(1)$^\prime$ gauge symmetry is radiatively broken via the Coleman-Weinberg mechanism, by which the U(1)$^\prime$ gauge boson ($Z^\prime$ boson) mass as well as the Majorana mass for the right-handed neutrinos are generated. The radiative U(1)$^\prime$ symmetry breaking also induces a negative mass squared for the SM Higgs doublet to trigger the electroweak symmetry breaking. In this context, we investigate a possibility to solve the SM Higgs vacuum instability problem. The model includes only three free parameters (U(1)$^\prime$ charge of the SM Higgs doublet, U(1)$^\prime$ gauge coupling and $Z^\prime$ boson mass), for which we perform parameter scan, and identify a parameter region resolving the SM Higgs vacuum instability. We also examine naturalness of the model. The heavy states associated with the U(1)$^\prime$ symmetry breaking contribute to the SM Higgs self-energy. We find an upper bound on $Z^\prime$ boson mass, $m_{Z^\prime} \lesssim 6$ TeV, in order to avoid a fine-tuning severer than 10 % level. The $Z^\prime$ boson in this mass range can be discovered at the LHC Run-2 in the near future.

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