Here you can find more information about neutrinos:

http://wwwlapp.in2p3.fr/neutrinos/aneut.html

Thanks for your reply. I was stimulated to ask the question by an article in last weeks New Scientist discussing the decay of Silicon 32 (half life a70 or sa days. Experiments measuring its (beta)decay showed a seasonal variation in rate synchronised with earth/sun distance. No systematic errors in the measurements could be found and an experiment using a long lived beta decay isotope should have ironed out this variation but did not. The authors idea was that the neutrino flux from the sun which has a seasonal variation of about 3% could if account for this if neutrino/neutron interaction could cause beta decay.

If you are interested I will rescue the article and send more details.

Si32 decays by neutron/antineutrino mechanism. A neutrinoneutron decay would look the same to a beta counter.