Neutrino oscillations in the early universe: A real-time formulation

Journal Article · Sat Oct 15 00:00:00 EDT 2005 · Physical Review. D, Particles Fields

DOI:https://doi.org/10.1103/PhysRevD.72.085016· OSTI ID:20713770

Ho, C M ^[1]; Boyanovsky, D ^[1]; Vega, H.J. de ^[2]

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1. Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, Pennsylvania 15260 (United States)
2. LPTHE, Universite Pierre et Marie Curie (Paris VI) et Denis Diderot (Paris VII), Laboratoire Associe au CNRS UMR 7589, Tour 24, 5eme. etage, 4, Place Jussieu, 75252 Paris, Cedex 05 (France)

Neutrino oscillations in the early universe prior to the epoch of primordial nucleosynthesis is studied by implementing real-time nonequilibrium field theory methods. We focus on two flavors of Dirac neutrinos, however, the formulation is general. We obtain the equations of motion for neutrino wave packets of either chirality and helicity in the plasma allowing for CP asymmetry. Contributions nonlocal in space-time to the self-energy dominate over the asymmetry for T > or approx. 3-5 MeV if the lepton and neutrino asymmetries are of the same order as the baryon asymmetry. We find a new contribution which cannot be interpreted as the usual effective potential. The mixing angles and dispersion relations in the medium depend on helicity. We find that resonant transitions are possible in the temperature range 10 < or approx. T<<100 MeV. Near a resonance in the mixing angle, the oscillation time scale in the medium as compared to the vacuum is slowed down substantially for small vacuum mixing angle. The time scale of oscillations speeds up for off-resonance high energy neutrinos for which the mixing angle becomes vanishingly small. The equations of motion reduce to the familiar oscillation formulae for negative helicity ultrarelativistic neutrinos, but include consistently both the mixing angle and the oscillation frequencies in the medium. These equations of motion also allow to study the dynamics of right handed as well as positive helicity neutrinos.

• OSTI ID: 20713770
• Journal Information: Physical Review. D, Particles Fields, Vol. 72, Issue 8; Other Information: DOI: 10.1103/PhysRevD.72.085016; (c) 2005 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
• Country of Publication: United States
• Language: English

Related Subjects

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
ASYMMETRY
BARYONS
CHIRAL SYMMETRY
CHIRALITY
COSMOLOGY
CP INVARIANCE
DISPERSION RELATIONS
EQUATIONS OF MOTION
HELICITY
MEV RANGE
NEUTRINO OSCILLATION
NEUTRINOS
NUCLEOSYNTHESIS
OSCILLATIONS
POTENTIALS
QUANTUM FIELD THEORY
RELATIVISTIC RANGE
SELF-ENERGY
SPACE-TIME
UNIVERSE
WAVE PACKETS
WEINBERG ANGLE