EAGER: Toward the Experimental Detection of Cosmic Relic Neutrinos

Massachusetts Institute Of Technology, Cambridge MA

Investigators

Abstract

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.