Neutrino absorption

These two examples of neutrino absorption reactions illustrate the procedures used in calculating the neutrino... 

In the previous Section we noted that the typical temperature, above which the star becomes opaque to neutrinos is Topac 0.4 4- 3 MeV, where we ignore here the differences in the absorption/production properties of different neutrino flavors [45], Saying neutrino we actually will not distinguish neutrino and antineutrino, although their absorption/production could be different. If we assume an initial temperature of To < T%pac, the star radiates neutrinos directly from the interior region. For To > T"po/P the neutrino transport to the surface is operative and leads to a delay of the cooling evolution. 

Strengthened by absorption of high-energy neutrinos, the shock wave expels the outer layers. Seen from outside, the star appears to have exploded. On Earth, this fabulous event is greeted with the joyous shout of Supernova ... 

Many of the nuclear reactions that provide the energy of the stars also result in the emission of neutrinos. Because of the small absorption cross sections for neutrinos interacting with matter (o lhs 10-44 cm2), these neutrinos are not generally absorbed in the sun and other stars. (This loss of neutrinos corresponds to a loss of 2% of the energy of our sun.) Because of this, the neutrinos are a window into the stellar interior. The small absorption cross sections also make neutrinos difficult to detect, with almost all neutrinos passing through planet Earth without interacting. 

Assume an absorption cross section of 10-44 cm2 for solar neutrinos interacting with matter. Calculate the probability of a neutrino interacting as it passes through Earth. 

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