标题： 通过参数荧光探测宇宙中微子背景 显示英文标题

标题： Probing Cosmic Neutrino Background through Parametric Fluorescence

摘要： 我们指出，大爆炸遗留的中微子可能在分子系统中引发参数荧光，这为发现宇宙中微子背景提供了一种新方法。 通过与分子能级相干散射，一个大质量中微子可以自发“衰变”为一个较轻的中微子和一个红外信号光子，即$\nu^{}_{i} + M \to \nu^{}_{j} + \gamma^{}_{\rm S} + M$，其中分子态$M$在散射后保持不变。 由于不同辐射体的振幅相位匹配，速率会相干增强，并与环境偶极子密度的平方成正比。 当中微子的能量传递与分子能级差一致时，荧光将处于共振状态。 我们发现，通过磁偶极跃迁，在共振峰处对于一个空间尺寸为$l=3~{\rm m}$的标称靶材，$\nu^{}_{i} \to \nu^{}_{j} + \gamma^{}_{\rm S}$的事件率可达$R \sim 5~{\rm yr}^{-1}$（或$10~{\rm yr}^{-1}$）（对于狄拉克中微子或马约拉纳中微子）。 由斯塔克效应引起的宇称混合可能有助于进一步放大信号速率。 显示英文摘要

摘要： We point out that relic neutrinos from the Big Bang may induce the parametric fluorescence in molecular systems, which offers a novel way to discover cosmic neutrino background. By coherently scattering with molecular energy levels, a massive neutrino can spontaneously ``decay" into a lighter neutrino and an infrared signal photon, i.e., $\nu^{}_{i} + M \to \nu^{}_{j} + \gamma^{}_{\rm S} + M$, where the molecular state $M$ remains unchanged after the scattering. Because the amplitudes of different radiants are matched in phase, the rate is coherently enhanced and proportional to the squared density of ambient dipoles. When the energy transfer from neutrinos coincides with the molecular energy-level difference, the fluorescence will be on resonance. We find that the event rate for $\nu^{}_{i} \to \nu^{}_{j} + \gamma^{}_{\rm S}$ at the resonance peak through the magnetic dipole transition can reach $R \sim 5~{\rm yr}^{-1}$ (or $10~{\rm yr}^{-1}$) for Dirac (or Majorana) neutrinos for a nominal target with a spatial dimension of $l=3~{\rm m}$. Parity mixing by the Stark effect may help to further magnify the signal rate.