arXiv 0902.42782009-02hep-phastro-ph.CO

EW I标度附近产生的惰性中微子：混合角、MSW共振和产生率

Sterile neutrinos produced near the EW scale I: mixing angles, MSW resonances and production rates

Jun Wu, Chiu-Man Ho, Daniel Boyanovsky

备注：: 31 pages
发表信息：: Phys.Rev.D80:103511,2009
DOI：: 10.1103/PhysRevD.80.103511

摘要：

我们研究了在区域$T\sim M_W$中产生不育中微子的扩展超出了标准模型的跷跷板质量矩阵起源于汤川耦合到类希格斯标量的质量和VEV的顺序的电弱标度。无菌中微子是由标量和标准模型矢量玻色子衰变产生的。从标准模型和超越标准模型的自能出发，得到了介质的折射率、色散关系、混合角和产生率，包括右手无菌中微子的产生率。对于$1 \lesssim M_W/T \lesssim 3$，我们发现窄MSW共振与$k \lesssim T$的左手和右手的中微子，即使在（活跃）中微子部门的轻子不对称的情况下，以及非常低的能量（$k/T \ll |ξ|$）窄MSW共振轻子不对称的存在下，从WMAP和BBN的边界一致。对于小的真空混合角，与观测范围一致，自能的吸收部分导致非常接近共振的强阻尼区，导致传播模式的\emph{exact}简并性，伴随着绝热性的崩溃。我们认为，宇宙膨胀席卷共振，\emph{resonant and non-resonant}无菌中微子生产的结果在一个高度\emph{non-thermal}分布函数增强在小动量$k < T$，在小尺度上的自由流长度和传递函数的潜在重要后果。

英文摘要：

We study the production of sterile neutrinos in the region $T\sim M_W$ in an extension beyond the standard model with the see-saw mass matrix originating in Yukawa couplings to Higgs-like scalars with masses and vev's of the order of the electroweak scale. Sterile neutrinos are produced by the decay of scalars and standard model vector bosons. We obtain the index of refraction, dispersion relations, mixing angles in the medium and production rates including those for right-handed sterile neutrinos, from the standard model and beyond the standard model self-energies. For $1 \lesssim M_W/T \lesssim 3$ we find narrow MSW resonances with $k \lesssim T$ for both left and right handed neutrinos even in absence of a lepton asymmetry in the (active) neutrino sector, as well as very low energy ($k/T \ll |ξ|$) narrow MSW resonances in the presence of a lepton asymmetry consistent with the bounds from WMAP and BBN. For small vacuum mixing angle, consistent with observational bounds, the absorptive part of the self-energies lead to a strong damping regime very near the resonances resulting in the \emph{exact} degeneracy of the propagating modes with a concomitant breakdown of adiabaticity. We argue that cosmological expansion sweeps through the resonances, \emph{resonant and non-resonant} sterile neutrino production results in a highly \emph{non-thermal} distribution function enhanced at small momentum $k < T$, with potentially important consequences for their free streaming length and transfer function at small scales.

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