Abstract
We explore the potential of measurements of cosmological effects, such as neutrino spectral distortions from the neutrino decoupling and neutrino clustering in our Galaxy, via cosmic neutrino capture on tritium. We compute the precise capture rates of each neutrino species including such cosmological effects to probe them. These precise estimates of capture rates are also important in that the would-be deviation of the estimated capture rate could suggest new neutrino physics and/or a non-standard evolution of the universe. In addition, we discuss the precise differences between the capture rates of Dirac and Majorana neutrinos for each species, the required energy resolutions to detect each neutrino species and the method of reconstruction of the spectrum of cosmic neutrinos via the spectrum of emitted electrons, with emphasis on the PTOLEMY experiment.
Highlights
The CνB has not yet been observed in a direct way
As a β-decaying nucleus, tritium is an appropriate candidate due to its availability, high neutrino capture cross section, low Q-value and long lifetime with a half-life of t1/2 = 12.32 years. In this method using a tritium target, provided that an extremely good energy resolution can be obtained, the signature of the capture of one neutrino species νi with energy Eνi is a peak in the electron energy spectrum at an energy of above the β decay endpoint1, where mlightest is the lightest mass species of neutrinos
We explore the potential of measurements and constraints on such cosmological effects via cosmic neutrino capture on tritium in more detail
Summary
We consider the cosmology of relic neutrinos. We review the history of the CνB in the instantaneous decoupling limit. Page 3 of 19 344 logical effects such as the neutrino spectral distortions in the neutrino decoupling and gravitational clustering of relic neutrinos. We calculate the precise number density of cosmic neutrinos in the present universe, including the neutrino spectral distortions in the decoupling and gravitational clustering
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