Direct Neutrino Mass Searches

Neutrino flavor oscillation experiments have demonstrated that the three Standard Model neutrino flavor eigenstates are mixed with three mass eigenstates whose mass eigenvalues are nondegenerate. The oscillation experiments measure the differences between the squares of the mass eigenvalues but tell us nothing about their absolute values. The unknown absolute neutrino mass scale has important implications in particle physics and cosmology. Beta decay endpoint measurements are presented as a model-independent method to measure the absolute neutrino mass. The Karlsruhe Tritium Neutrino Experiment (KATRIN) is explored in detail.