Etudes des proprietes des neutrinos dans les contextes ...

tel-00450051, version 1 - 25 Jan 2010
)
-1
(km
µ
,
λ
5
10
4
10
3
10
2
10
10
1
-1
10
synch bipolar split
50 100 150 200
r (km)
Figure 5.3: Radial profiles of the neutrino self-interaction parameter µ(r) =
√ 2GF (N + N) and of the matter-interaction parameter λ(r) = √ 2 GF N e −, in
the range r ∈ [10, 200] km. Taken from [64]
5.2 The different collective behaviours
To study all the different phenomena that occur near the neutrino sphere, we
make several restrictions and approximations. We consider the matter density
large enough that the H-resonance due to the MSW effect, driven by the atmospheric
mass squared difference and the mixing angle θ13, is the only relevant
resonance in the problem (see section 1.2.2). We therefore reduce the problem to
a 2-flavour problem (νe and νx), with θV = θ13. Note that contrary to the MSW
effect, the flavour conversions occur via the process νe¯νe → νx¯νx. Therefore, the
net flavor-lepton number is conserved 4 .
4 This is exactly true in the vacuum only case. When matter is included this number is not
exactly conserved.
95
λ
µ