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arXiv 1306.6108hep-ph
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辐射诱导的II型跷跷板和类矢量5/3电荷夸克

Radiatively Induced Type II seesaw and Vector-like 5/3 Charge Quarks

R. Franceschini, R. N. Mohapatra

摘要:

要理解具有TeV尺度SM三重态希格斯玻色子的II型跷跷板模型中的小中微子质量,需要将其与标准模型希格斯二重态H的耦合降低到eV到KeV的量级,这是相对于弱尺度的$10^{-11}-10^{-8}$的微调。我们提出了一个超对称扩展的II型跷跷板模型,这种维数小耦合辐射诱导,从而使其自然的小。这个模型有一个奇异的矢量夸克偶,它包含一个带电荷为5/3的夸克X和一个顶夸克t '。我们详细讨论了该模型的唯象,特别注意奇异重夸克与模型标量相互作用的后果。详细讨论了无中微子双β衰变和LHC实验的意义。值得注意的是,在这个模型中,跷跷板三重态和重夸克都可以在对撞机上以大量不同的特征出现,包括一些与极小模型显著不同的特征。根据耦合层次的选择,重夸克和跷跷板三重态的衰变可能会受到比标准LHC搜索的边界更紧或更松的边界的约束。此外,我们指出了一个新的短距离贡献的无中微子双β衰变介导的同时传播的II型三重态和奇异费米子。值得注意的是,这种对无中微子双β衰变的贡献在参数上与产生的中微子质量的尺度完全无关。

英文摘要:

Understanding small neutrino masses in type II seesaw models with TeV scale SM triplet Higgs bosons requires that its coupling with the standard model Higgs doublet H be dialed down to be order eV to KeV, which is a fine-tuning by a factor of $10^{-11}-10^{-8}$ with respect to the weak scale. We present a SUSY extension of the type II seesaw model where this dimensionful small coupling is radiatively induced, thus making its smallness natural. This model has an exotic vector-like quark doublet which contains a quark X with electric charge 5/3 and a top partner t'. We discuss in details the phenomenology of the model paying special attention to the consequences of the interactions of the the exotic heavy quarks and the scalars of the model. Implications for neutrinoless double beta decay and for the LHC experiments are discussed in detail. Remarkably, in this model both the seesaw triplet and the heavy quarks can manifest at colliders in a host of different signatures, including some that significantly differ from those of the minimal models. Depending on the choice of the hierarchy of couplings, the decay of the heavy quarks and of the seesaw triplet may be subject to bounds that can be tighter or looser than the bounds from standard LHC searches. Furthermore we point out a new short-distance contribution to neutrinoless double beta decay mediated by the simultaneous propagation of the type II triplet and exotic fermions. Remarkably this contribution to the neutrinoless double beta decay is parametrically quite independent from the scale of the generated neutrino mass.

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