Measuring neutrino mass with radioactive ions in a storage ring

Abstract

We propose a method to measure the neutrino mass kinematically using beams of ions which undergo beta decay. 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. Then, 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 ν < 0.2 eV, it is necessary to control the ion momentum with a precision better than δp/p < 10 −5 , identify suitable nuclei with low Q-values (in the few to ten keV range), and one must be able to observe at least O(10 18 ) decays.

EURONU WP6 2009 yearly report: Update of the physics potential of Nufact, superbeams and betabeams

“…In Ref. [11] a method has be proposed to measure the neutrino mass kinematically using beams of ions which undergo beta decay. 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, see Fig.…”

“…Electrons moving in the backward direction in the laboratory frame are counted by the detector. Taken from Ref [11]…”

Ultra-low Q values for neutrino mass measurements

“…Moreover, if the time of each decay can be tagged by observing an associated gamma or x-ray photon, the spectrometer can be operated in the more sensitive time-of-flight (MAC-E TOF) mode [5]. Finally, it might be possible to combine our ideas with the methods proposed in [6][7][8] to measure also the energy and momentum of the recoil nucleus. All these effects should help to reduce the required number of stored ions, even though the experiment will still be extremely challenging.…”

“…If KATRIN should not see a positive signal, new experimental techniques would be required to push the sensitivity to even smaller m ν . For example, it has been proposed to study nuclear recoils in bound state β decay of tritium [6], to reconstruct the electron and nuclear kinematics in tritium decay [7], or to measure the electron flux near the tritium endpoint in a storage ring [8]. However, all of these proposals are limited by the large Q value of tritium, which makes the neutrino mass a small effect.…”