Non-unitary three-neutrino mixing in the early Universe

Abstract

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, $N_{\mathrm{eff}}$. 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 $N_{\mathrm{eff}}$ 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.

16 pages, 3 figures, 3 tables

References in corpus (15)

• In the Realm of the Hubble tension $-$ a Review of Solutions
• Towards a precision calculation of $N_{\mathrm{eff}}$ in the Standard Model II: Neutrino decoupling in the presence of flavour oscillations and finite-temperature QED
• A precision calculation of relic neutrino decoupling
• Non-unitarity of the leptonic mixing matrix: Present bounds and future sensitivities
• Non-unitary neutrino mixing and CP violation in the minimal inverse seesaw model
• Correlation between the Charged Current Interactions of Light and Heavy Majorana Neutrinos
• Thermalisation of sterile neutrinos in the early Universe in the 3+1 scheme with full mixing matrix
• Multi-momentum and multi-flavour active-sterile neutrino oscillations in the early universe: role of neutrino asymmetries and effects on nucleosynthesis
• Non-unitary neutrino mixing in short and long-baseline experiments
• Primordial neutrino asymmetry evolution with full mean-field effects and collisions
• Two sides of the same coin: sterile neutrinos and dark radiation. Status and perspectives
• Cosmological radiation density with non-standard neutrino-electron interactions
• A review of neutrino decoupling from the early universe to the current universe
• A full parametrization of the $9\times 9$ active-sterile flavor mixing matrix in the inverse or linear seesaw scenario of massive neutrinos
• Status of Anomalies and Sterile Neutrino Searches at Nuclear Reactors

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• Scale and redshift dependent limits on cosmic neutrino properties
• Big Bang Nucleosynthesis as a probe of non-standard neutrino interactions and non-unitary three-neutrino mixing
• Update on non-unitary mixing in the recent NO$\nu$A and T2K data
• Standard and Non-Standard Aspects of Neutrino Physics
• Testing lepton non-unitarity with the next generation of Germanium-based CE$\nu$NS reactor experiments
• Impact of unitarity violation on sensitivity of the leptonic CP phase at Hyper-Kamiokande and DUNE