The relic neutrino composition as seen from Earth

Abstract

Being generated, the relic neutrino background contained equal fractions of electron $\nu_e$, muon $\nu_\mu$, and taon $\nu_\tau$ neutrinos. We show that the gravitational field of our Galaxy and other nearby cosmic objects changes this composition near the Solar System, enriching it with the heaviest neutrino $nu_3$. This mass state is almost free of the electron component (only $\sim 2\%$ of $\nu_e$) and contains more muon component than the tau one. As a result, the relic background becomes enriched with taon and particularly muon neutrinos. The electron relic neutrinos are the rarest for a terrestrial observer: instead of $1/3$, the relic background may contain only $\gtrsim 20\%$ of them.