Etudes des proprietes des neutrinos dans les contextes ...

tel-00450051, version 1 - 25 Jan 2010
Figure 3.1: Time evolution of neutrino luminosity and average energy of the numerical
supernova model used in. The dashed line is for νe, solid line for νe, and dotdashed
line for νx (= each of νµ,νµ,ντ and ντ ). The core bounce time is 3.4 msec before the
neutronization burst of νe’s. Taken from [114]
the shock reaches a zone with density about 10 11 g.cm −3 (shock breakout) a few
milliseconds after the bounce and the electron neutrinos behind the shock are
released in a few milliseconds. This neutrino emission is usually called a prompt
electron neutrino burst or neutronization burst, to be distinguished from the thermal
production of all neutrino flavors. The neutronization burst has a luminosity
of about 6 × 10 53 erg.s −1 and carries away a few 10 51 erg in a few milliseconds
which is too short to carry away a significant part of the electron lepton number
of the core, which remains trapped. Only the low-density periphery of the protoneutron
star is neutronized which represents a few tenths of a solar mass so that
most of the leptons remain trapped in the inner core.
The cooling stage.
As the core collapse proceeds, a second stage of neutrino emission begins. The
flux of theses neutrinos consist of νe, νe, νµ, νµ, ντ and ντ. They have energy in
the range of 15 to 20 MeV. This corresponds to an emission temperature of about
5-6 MeV if one assumes a thermal distribution with zero chemical potential. Neu-
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