Etudes des proprietes des neutrinos dans les contextes ...

tel-00450051, version 1 - 25 Jan 2010
Figure 5.9: Neutrino spectra at the neutrino sphere (thin lines) and beyond the
dense-neutrino region (thick lines) for the schematic SN model described in the
text.ω < 0 is for antineutrinos, ω > 0 for neutrinos. Taken from [103]
where Pω = |Pω| and ˆ Hω ≡ Hω/|Hω| is a unit vector in the direction of the
Hamiltonian. In the limit µ → ∞ all polarization vectors are aligned with each
other in a direction given by the initial condition. In the opposite limit, µ → 0,
the solution is given by
Hω → (ω − ω 0 c )B, (5.61)
where ω0 c ≡ ωc(µ → 0). All Hamiltonians and thus all Pω with ω > ωc are
aligned with B, whereas those with ω < ω0 c are anti-aligned. Therefore, we have
a spectral split at the frequency
ωsplit = ω 0 c
(5.62)
which usually is not equal to zero. To finish with this subsection concerning the
spectral split feature, we show the Fig.(5.9). When the spectra is represented in
terms of the oscillation frequency ω = ∆m 2 /2E instead of the energy, the split
phenomenon appears clearer. The flavour conversion induced by the neutrinoneutrino
interaction acts for neutrino as well as for anti-neutrinos. However,
because of the supernova environment, there is a deleptonization flux implying
an excess of νe in comparison with the ¯νe, in this case ωsplit > 0. Consequently,
the νe flux part with energies below Esplit (or the oscillation frequency above
ωsplit) will not undergo flavour conversion because no corresponding ¯νe will be
there to annihilate.
5.2.4 Phenomenological implications on the fluxes
To observe the phenomenological consequences of such typical behaviours for the
neutrino evolution, we have included in our previous numerical code the neutrino-
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