We investigate an extension of the Minimal Standard Model by right-handedneutrinos (the $\nu$MSM) to incorporate neutrino masses consistent withoscillation experiments. Within this theory, the only candidates for darkmatter particles are sterile right-handed neutrinos with masses of a few keV.Requiring that these neutrinos explain entirely the (warm) dark matter, we findthat their number is at least three. We show that, in the minimal choice ofthree sterile neutrinos, the mass of the lightest active neutrino is smallerthan ${\cal O}(10^{-5})$ eV, which excludes the degenerate mass spectra ofthree active neutrinos and fixes the absolute mass scale of the other twoactive neutrinos.
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机译：我们研究了右手中微子（$ \ nu $ MSM）对最小标准模型的扩展，以纳入与振荡实验一致的中微子质量。在这个理论中，暗物质粒子的唯一候选者是质量为几keV的无菌右旋中微子，要求这些中微子完全解释（温暖）暗物质，我们发现它们的数量至少为三个。我们表明，在最少选择的三个无菌中微子中，最轻的活跃中微子的质量小于$ {\ cal O}（10 ^ {-5}）$ eV，这排除了三个活跃中微子的简并质谱并固定了其他两个活性中微子的绝对质量标度。
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