Measuring Neutrino Mass with Radioactive Ions in a Storage Ring

A method to measure the neutrino mass kinematically using beams of ions which undergo beta decay is proposed. The idea is to tune the ion beam momentum so that in most decays, the electron is forward moving with respect to the beam, and only in decays near the endpoint is the electron moving backwards. By counting the backward moving electrons one can observe the effect of neutrino mass on the beta spectrum close to the endpoint. In order to reach sensitivities for m(v) < 0.2 eV, it is necessary to control the ion momentum with a precision better than dp/p < 10(-5), identify suitable nuclei with low g-values (in the few to ten keV range), and one must be able to observe at least O(10(18)) decays.