The neutrinos are 3 of the 12 fundamental particles out of which the matter
is made of. Their mass is one of the burning questions of particle physics
Up to recently neutrinos were assumed to be massless, but the actual measurements
of neutrinos from the sun and of neutrinos created in the atmosphere by cosmic rays
indicate that they have some probably very small mass.
The Mainz Neutrino Mass Experiment measures
the shape of the beta decay spectrum of tritium very
precisely. This method is presently the most
sensitive direct one in search for the neutrino mass.
Summer 2001, preparing run Q11: