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arXiv 0705.1729hep-ph
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如何找到nuMSM的中性轻子?

How to find neutral leptons of the nuMSM?

Dmitry Gorbunov, Mikhail Shaposhnikov

摘要:

用三个质量小于电弱标度的单重态费米子扩展标准模型,可以同时解释宇宙的中微子振荡、暗物质和重子不对称性。我们讨论了在这个模型中中性轻子的性质以及在粒子物理实验中寻找它们的方法。特别是,我们建立了一个下限和上限的中性轻子的相互作用强度来自宇宙学的考虑和中微子振荡的数据。我们分析了中性轻子在不同介子衰变和$pp$碰撞中的产生。我们详细研究了中性轻子的衰变,并根据已有的实验数据和大爆炸核合成建立了中性轻子质量的下限。我们认为,寻找一个特定的失踪的能量信号在K介子衰变将允许加强相当大的界限中性费米子耦合,并找到或明确排除它们低于K介子阈值。为了进入宇宙学上感兴趣的参数范围,质量高于K介子质量,需要使用强质子束进行类似于CERN PS191实验的专门搜索。我们认为,使用CNGS,NuMI,T2 K或NuTeV光束可以允许搜索单重轻子魅力以下的大部分参数空间的nuMSM。在2-5 GeV的质量区间内寻找单重态费米子需要相当大的质子加速器强度的增加,或者需要对超过10^{10}个B介子衰变的运动学进行详细的分析。

英文摘要:

An extension of the Standard Model by three singlet fermions with masses smaller than the electroweak scale allows to explain simultaneously neutrino oscillations, dark matter and baryon asymmetry of the Universe. We discuss the properties of neutral leptons in this model and the ways they can be searched for in particle physics experiments. We establish, in particular, a lower and an upper bound on the strength of interaction of neutral leptons coming from cosmological considerations and from the data on neutrino oscillations. We analyse the production of neutral leptons in the decays of different mesons and in $pp$ collisions. We study in detail decays of neutral leptons and establish a lower bound on their mass coming from existing experimental data and Big Bang Nucleosynthesis. We argue that the search for a specific missing energy signal in kaon decays would allow to strengthen considerably the bounds on neutral fermion couplings and to find or definitely exclude them below the kaon threshold. To enter into cosmologically interesting parameter range for masses above kaon mass the dedicated searches similar to CERN PS191 experiment would be needed with the use of intensive proton beams. We argue that the use of CNGS, NuMI, T2K or NuTeV beams could allow to search for singlet leptons below charm in a large portion of the parameter space of the nuMSM. The search of singlet fermions in the mass interval 2-5 GeV would require a considerable increase of the intensity of proton accelerators or the detailed analysis of kinematics of more than 10^{10} B-meson decays.

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