EAGER: Toward the Experimental Detection of Cosmic Relic Neutrinos

在对宇宙微波背景辐射（CMB）进行初步观测后进行的一系列测量有助于将观测宇宙学转变为一门极具预测性的科学。宇宙一致性模型的许多参数现在已经被测量出来，未来几十年对这些参数的进一步探索可能会揭示我们宇宙中更多隐藏的方面。尽管宇宙学的许多预测现在已经实现，但仍有其他预测未被观测到。对宇宙大爆炸产生的宇宙中微子背景的直接探测是中微子物理学和宇宙学的基本挑战之一。像它们的光子对应物一样，宇宙中残余中微子的存在是预料之中的；然而，它的直接观测仍然难以捉摸。对宇宙中微子遗迹的观测，或者相反，没有中微子遗迹的观测，是对该模型的重要验证。从实验的角度来看，直接观测残余中微子是一项极其困难的挑战。中微子温度T与CMB温度直接相关，预计T=1.95 K，即0.17 meV的能量。大多数传统的检测中微子的方法依赖于相互作用，这些相互作用对入射中微子的能量有一些阈值，通常比预测的残余中微子能量大很多个数量级。幸运的是，有一个很好的候选方法可以检测到这种低能中微子：放射性原子核上的中微子捕获。中微子捕获过程的信号是独特的：在β衰变能谱的端点能量之上的单能峰。有了足够分辨率和目标质量的探测器，至少在原则上，对宇宙中微子背景的探测似乎是可能的。这个EAGER奖项是为了奖励探索性的、高风险的、高回报的努力，以建立一个小型的新颖实验来测试这种高精度的检测技术。对于更广泛的影响，这个项目解决了直接探测宇宙中微子背景的搜索。如果成功，它将与粒子物理学、核物理学和天体物理学有重大的重叠。该技术设想的这种测量有潜在的分支，其他学科与低能电子计量显著的兴趣。

The series of measurements made after the initial observation of the Cosmic Microwave Background (CMB) Radiation has helped transform observational cosmology into an extremely predictive science. Many of the parameters of the cosmological concordance model have now been measured and further exploration of these parameters over the next few decades are likely to reveal even more hidden aspects of our universe. Although many of the predictions from cosmology have now been realized, there are others that remain unobserved. The direct detection of the Cosmic Neutrino Background produced from the primordial Big Bang stands as one of the fundamental challenges in both neutrino physics and cosmology. Like their photon counterparts, the existence of relic neutrinos in the cosmos is expected; yet, its direct observation remains elusive. Observation of the cosmic relic neutrinos or, conversely, the absence of such, stands as an important verification of the model.The direct observation of relic neutrinos is an extremely difficult challenge from an experimental perspective. The neutrino temperature, T, is related directly to the CMB temperature, and is expected to be T=1.95 K, or 0.17 meV in energy. Most conventional methods of detecting neutrinos rely on interactions that have some threshold for the energy of the incoming neutrino which is often many orders of magnitude larger than this predicted relic neutrino energy. Fortunately, there exists a good candidate by which such low energy neutrinos can be detected: neutrino capture on radioactive nuclei. The signal of the neutrino capture process is unique: a monoenergetic peak above the endpoint energy of the beta decay energy spectrum. With a detector of sufficient resolution and target mass, detection of the Cosmic Neutrino Background appears, at least in principle, to be possible. This EAGER award is for an exploratory, high-risk, high-payoff effort to build a small novel experiment to test this high precision detection technique.For Broader Impacts, this project addresses a search for the direct detection of the Cosmic Neutrino Background. If successful, it will have significant overlap with particle physics, nuclear physics and astrophysics. The technique envisioned for this measurement has potential ramifications for other disciplines with significant interest in low energy electron metrology.