Etudes des proprietes des neutrinos dans les contextes ...

tel-00450051, version 1 - 25 Jan 2010
Figure 7.4: Electron anti-neutrino fluxes on Earth, in the case of adiabatic (“cold”
spectrum, solid) and non-adiabatic (“hot” spectrum, dashed) conversions in the
star. t=1s
resonance region, important modifications of the neutrino fluxes occur. The
presence of the shock wave renders the neutrino flavor conversion in this region
non-adiabatic. Therefore the neutrino spectra on Earth remains “hot” (Figure
7.4). Note that the adiabatic and non-adiabatic spectra will cross at some energy,
which in this case, is Eν = 20 MeV. These different regimes produce specific
signatures on the time signals, as we discuss now.
The positron signals in an observatory
We are considering the positron signal emitted from the inverse β reactions in the
water Cerenkov detector. The positron spectrum seen in a detector, Φe +(Ee +), is
given by
dσ
Φe +(Ee +) = Np dE¯νe F¯νe
(7.6)
dEe +
where Np is the number of protons in the detector, F¯νe is the electron antineutrino
flux on Earth and dσ/dEe + is the differential cross section. Note that the positron
spectrum is not the direct image of the ¯νe flux and a certain correlation function
has to be taken into account. More details concerning the positron spectrum can
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