Etudes des proprietes des neutrinos dans les contextes ...

tel-00450051, version 1 - 25 Jan 2010
Flux Ratio
1.6
1.4
1.2
1
0.8
0.6
0 20 40 60 80 100
Neutrino Energy (MeV)
Figure 4.1: ¯νµ (lower curves) and ¯ντ (upper curves) flux ratios for a CP violating
phase δ = 180 ◦ over δ = 0 ◦ Eq.(4.38), as a function of neutrino energy. Results
at different distances from the neutron-star surface are shown, namely 250 km
(dotted), 500 km (dashed), 750 km (dot-dashed) and 1000 km (solid line). The
curves correspond to the normal hierarchy and sin 2 2θ13 = 0.19.
Effects on the fluxes inside the supernova
In order to show possible CP-violating effects on the νi fluxes, we will use the
ratio:
φνi (δ)
Rνi (δ) =
φνi (δ = 0◦ )
(4.38)
Figures 4.1 and 4.2 show the ¯νµ, ¯ντ and νµ, ντ flux ratios Eq.(4.38) for δ = 180 ◦
over for δ = 0 ◦ . One can see that large effects, up to 60 % are present for low
neutrino energies in the anti-neutrino case; while smaller effects, of the order of a
few percent, appear in the neutrino case. The effect of a non-zero delta over the
νµ, ντ fluxes as a function of neutrino energy is shown in Figure 4.3 at a distance
of 1000 km. We see that an increase as large as a factor of 8 (4) can be seen at low
energies in the νµ (ντ) spectra. A similar behavior is found in the anti-neutrino
case.
Practically all the literature concerning the neutrino evolution in core-collapse
supernovae ignore the Dirac phase, for simplicity. Our results justify this assumption
if such calculations make the hypothesis that the νµ (¯νµ) and ντ (¯ντ)
luminosities are equal and neglect the Vµ,τ. Our aim is to show the CP violating
effects in the case when νµ and ντ fluxes differ. We have explored various
differences between the νµ, ντ luminosities. We present here for example results
corresponding to 10 % variation, e.g. L 0 ντ = 1.1 L0 νµ or Tντ= 8.06 MeV while
Tνµ= 7.06 MeV. Figure 4.4 presents as an example the evolved νe, νµ neutrino
fluxes, at 1000 km from the neutron star surface, when Tνµ = Tντ. The different
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