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arXiv 2107.12802hep-ph
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弱标度右手中微子作为自发破缺$U(1)_{L_μ-L_τ}$的赝Goldstone费米子

Weak scale right-handed neutrino as pseudo-Goldstone fermion of spontaneously broken $U(1)_{L_μ-L_τ}$

Anjan S. Joshipura, Ketan M. Patel

摘要:

在超对称理论中,考虑了右手中微子成为整体$U(1)$对称性自发破缺的Goldstone费米子的可能性.这种费米子从超引力效应中获得质量,导致在电弱尺度下的RH中微子,其质量与引力子质量相似。实现这种情况的原型模型仅包含I型跷跷板机制所需的三个规范单重态超场。另外两个中微子的质量由$U(1)$破缺标度决定,这个破缺标度也可以在电弱标度附近。在这种情况下,轻中微子通过(a)与RH中微子混合(I型跷跷板),(b)与中性伴子混合($R$ -宇称破缺),(c)间接地通过RH中微子与中性伴子混合,以及(d)辐射修正获得质量。所有这些贡献所描述的一个小数目的基本参数相同的一组,并提供了一个非常受约束的和预测的中微子质量的框架,详细研究了各种选择的$U(1)$对称性。研究发现,如果软超对称破缺项是味普适的,则味无关的$U(1)$对称性不能描述中微子质量,而需要考虑味相关的对称性.考虑到一个特定的例子,$L_μ- L_τ$对称性,它表明,可行的中微子质量和混合,可以得到不引入任何味违反软部门。在此模型中计算出了Majoron的轻子耦合,并表明它与各种实验室、天体物理和宇宙学约束是一致的。中微子数据允许RH中微子和希格斯玻色子之间有相当大的耦合,这可以用来探测对撞机上的伪戈德斯通费米子,通过它的位移衰变顶点。

英文摘要:

Possibility of a Right-Handed (RH) neutrino being a Goldstone fermion of a spontaneously broken global $U(1)$ symmetry in a supersymmetric theory is considered. This fermion obtains mass from the supergravity effects leading to a RH neutrino at the electroweak scale with a mass similar to the gravitino mass. A prototype model realizing this scenario contains just three gauge singlet superfields needed for the type I seesaw mechanism. Masses of the other two neutrinos are determined by the $U(1)$ breaking scale which too can be around the electroweak scale. Light neutrinos obtain their masses in this scenario through (a) mixing with the RH neutrinos (type I seesaw), (b) mixing with neutralinos ($R$-parity breaking), (c) indirectly through mixing of the RH neutrinos with neutralinos, and (d) radiative corrections. All these contributions are described by the same set of a small number of underlying parameters and provide a very constrained and predictive framework for the neutrino masses which is investigated in detail for various choices of $U(1)$ symmetries. It is found that flavour independent $U(1)$ symmetries cannot describe neutrino masses if the soft supersymmetry breaking terms are flavour universal and one needs to consider flavour dependent symmetries. Considering a particular example of $L_μ- L_τ$ symmetry, it is shown that viable neutrino masses and mixing can be obtained without introducing any flavour violation in the soft sector. The leptonic couplings of Majoron are worked out in the model and shown to be consistent with various laboratory, astrophysical and cosmological constraints. The neutrino data allows sizeable couplings between the RH neutrinos and Higgsinos which can be used to probe the pseudo-Goldstone fermion at colliders through its displaced decay vertex.

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