Version francaise
, is measured since almost 50 years
using mainly the beta decay. The continuous spectrum of beta decay electrons terminates
at a maximal energy, which depends on the neutrino mass and on the emitting nucleus type.
The measurement of this spectrum and the very difficult measurement of the nucleus recoil
allows theoretically to determine the neutrino mass.
The most precise measurements are made using the beta decay of tritium. From those
measurements, we know today that the
neutrino mass is less than 5.1 eV.
Some recent measurements from 1995 and 1996 even let think that the neutrino
mass squared is negative (that is neutrino mass is imaginary!).
Some physicists even dare to do the hypothesis of a
tachyonic neutrino
(neutrino moving faster than light).
neutrino
can be obtained through the study of pion decay into muon.
For now, this kind of measurement has given
a mass less than 160 keV.
neutrino
is obtained through the study
of tau decay or thanks to high energy experiments like Aleph at CERN which, through
the study of decay channel of Z boson into tau allowed in 1995 to decrease
at 24 MeV
the superior limit on the mass.
Last update: 26/06/1999 : http://wwwlapp.in2p3.fr/neutrinos/amassehe3.html
Didier Verkindt