Monochromatic neutrino beams

In the last few years spectacular results have been achieved with thedemonstration of non vanishing neutrino masses and flavour mixing. The ultimategoal is the understanding of the origin of these properties from new physics.In this road, the last unknown mixing [Ue3] must be determined. If it is provedto be non-zero, the possibility is open for Charge Conjugation-Parity (CP)violation in the lepton sector. This will require precision experiments with avery intense neutrino source. Here a novel method to create a monochromaticneutrino beam, an old dream for neutrino physics, is proposed based on therecent discovery of nuclei that decay fast through electron capture. Suchnuclei will generate a monochromatic directional neutrino beam when decaying athigh energy in a storage ring with long straight sections. We also show thatthe capacity of such a facility to discover new physics is impressive, so thatfine tuning of the boosted neutrino energy allows precision measurements of theoscillation parameters even for a [Ue3] mixing as small as 1 degree. We canthus open a window to the discovery of CP violation in neutrino oscillations