PT Journal
AU Gariazzo, S
   Martinez-Mirave, P
   Mena, O
   Pastor, S
   Tortola, M
TI Non-unitary three-neutrino mixing in the early Universe
SO Journal of Cosmology and Astroparticle Physics
JI J. Cosmol. Astropart. Phys.
PY 2023
BP 046
EP 18pp
VL 03
IS 3
DI 10.1088/1475-7516/2023/03/046
LA English
DE cosmological neutrinos; neutrino properties; neutrino theory
AB Deviations from unitarity in the three-neutrino mixing canonical picture are expected in many physics scenarios beyond the Standard Model. The mixing of new heavy neutral leptons with the three light neutrinos would in principle modify the strength and flavour structure of charged-current and neutral-current interactions with matter. Non-unitarity effects would therefore have an impact on the neutrino decoupling processes in the early Universe and on the value of the effective number of neutrinos, Neff. We calculate the cosmological energy density in the form of radiation with a non-unitary neutrino mixing matrix, addressing the possible interplay between parameters. Highly accurate measurements of Neff from forthcoming cosmological observations can provide independent and complementary limits on the departures from unitarity. For completeness, we relate the scenario of small deviations from unitarity to non-standard neutrino interactions and compare the forecasted constraints to other existing limits in the literature.
ER