CP violation effects on the neutrino degeneracy parameters in the Early Universe

Abstract

We explore possible CP violating effects, coming from the Dirac phase of the Maki-Nakagawa-Sakata-Pontecorvo matrix, on the neutrino degeneracy parameters, at the epoch of Big-Bang nucleosynthesis. We first demonstrate the conditions under which such effects can arise. In particular it requires that the initial muon and tau neutrino degeneracy parameters differ. Then we solve numerically the kinetic equations for the three flavour neutrino density matrix with the goal of quantifying the impact of the Dirac phase on the electron neutrino degeneracy parameter. The calculations include the vacuum term, the coupling to matter, the neutrino-neutrino interaction and the collisions. Effects on electron neutrino degeneracy parameter up to almost 1.% and on Yp of about 0.1% are found, depending on the initial conditions.

15 pages, 4 figures

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• Collisional instabilities of neutrinos and their interplay with fast flavor conversion in compact objects
• Resurrection of large lepton number asymmetries from neutrino flavor oscillations
• Primordial neutrino asymmetry evolution with full mean-field effects and collisions
• Neutrino flavor transformation in the lepton-asymmetric universe
• The neutrino signal at HALO: learning about the primary supernova neutrino fluxes and neutrino properties
• Neutrino Magnetic Moment, CP Violation and Flavor Oscillations in Matter
• The neutrino-neutrino interaction effects in supernovae: the point of view from the 'matter' basis
• Constraints on primordial lepton asymmetries with full neutrino transport
• Lepton asymmetry, neutrino spectral distortions, and big bang nucleosynthesis
• Self-consistency in models of neutrino scattering and fast flavor conversion
• Strange mechanics of the neutrino flavor pendulum
• Open issues in neutrino astrophysics
• Lepton Flavor Asymmetries: from the early Universe to BBN
• Search for new physics with neutrinos at Radioactive Ion Beam facilities
• Large-scale asymmetry in the distribution of galaxy spin directions -- analysis and reproduction
• Time dependent signatures of core-collapse supernova neutrinos at HALO
• Impact of CP-violation on neutrino lepton number asymmetries revisited
• The Universe at the MeV era: neutrino evolution and cosmological observables
• Neutrinos and core-collapse supernovae