Wolfgang Pauli was a scientist with "NO" in his mind. Pauli's exclusion principle, that two electrons can't occupy the same quantum state is fundamental for all the chemistry. In 1930, in order to explain a continuous energy distribution of the electrons (and positrons) emitted during b decays, Pauli suggested the existence of a new particle, so small, that " you have no chance to find it". It was called neutrino by E. Fermi and discovered only in 1956 by C. Cowan and F. Reines. |
Neutrinos are detected by reactions opposite to b decay, like 37Cl→38Ar. Because the probability of such a reaction is very small with a quite big background, these experiments need big installations placed deep under the Earth surface (on the photo - a boat ride on the surface of the detector lake in Kamioka in Japan).
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In 1998 some results of the experiment performed in old Kamioka mine (1000 m below the surface) indicated that, possibly, neutrinos have a non-zero mass. And that the three types of neutrinos flying form Sun can change in flight from one to another [1]. |
In 2003, experiments from Kamioka laboratory |
20 years old Pauli was looking for a job and had to deliver a lecture. The president, a well know professor, commented that Pauli's calculations are not quite clear for him. Pauli answered that physics is difficult and no everyone has to understand it. |
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Another picturesque installation catching neutrinos is under “Big Stone” – Gran Sasso in Abruzzo, Italy. |
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“The Super Nova early warning system” |
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It was Italian scientist Bruno Pontcorvo, emigrated |
SN 1987A was the last super-nova visible in our skies — and the first from which scientists detected neutrinos. [2] In 2002, a flux of electron neutrinos with the intensity of 1.76x106cm-2s-1 and a flux of the heavier neutrinos with the intensity of
3.41x106cm-2s-1 were observed in Sudbury experiment (=another old mine, in Canada), finally in agreement with Solar nuclear-reaction models.
Limits on neutrino masses are ne<2.8 eV and the sum 0.05 eV
< ne +
nµ
+ nτ
< 8.4 eV (giving not more than 18% of the missing Universe mass). |
[1] Ashie Y et al. Evidence for an oscillatory signature in atmospheric neutrino oscillations, Physical Review Letters 93 (10): Art. No. 101801 Sep 3 2004 . |