ABSTRACT
In this chapter direct methods for neutrino mass determinations are discussed. The classical way to perform such searches for ν¯e is to investigate β-decay. From the historical point of view this process played a major role (see chapter 1) because it was the motivation for W Pauli to introduce the neutrino. Many fundamental properties of weak interactions were discovered by investigating β-decay. For an extensive discussion on weak interactions and β-decay see [Sch66,Sie68,Wu66,Kon66,Mor73, Rob88, Gro90, Wil01, Wei02, Ott08].
