Development of a Relic Neutrino Detection Experiment at PTOLEMY: Princeton Tritium Observatory for Light, Early-Universe, Massive-Neutrino Yield

The direct detection of relic neutrinos from the Big Bang was proposed in a paper by Steven Weinberg in 1962 [Phys. Rev. 128:3 (1962) 1457]. The signal for relic neutrino capture on tritium is the observation of electron kinetic energies emitted from a tritium target that are above the β-decay endpoint. The requirements on the experimental energy resolution for relic neutrino identification are constrained by the thermal model for neutrino decoupling in the early universe that predicts a present-day average neutrino kinetic energy of 1.7×10−4eV, neutrino mass mixing parameters that indicate mass eigenstates at least as massive as 0.05eV, and cosmological input from WMAP+SPT, and other sources, on the sum of the masses of the light neutrino species in thermal equilibrium in the early universe to be constrained to less than approximately 0.3eV. The parameters for a relic neutrino experiment require 100 grams of weakly-bound atomic tritium, sub-eV energy resolution commensurate with the most massive neutrinos with electron-flavor content, and below microHertz of background rate in a narrow energy window above the tritium endpoint. The PTOLEMY experiment (Princeton Tritium Observatory for Light, Early-Universe, Massive-Neutrino Yield) aims to achieve these goals through a combination of a large area surface-deposition tritium target