Determination of the pattern of neutrino masses at a Neutrino Factory

Abstract

We study the precision to which the sign of \delta m_{32}^2 can be determined at a neutrino factory, as a function of stored energies and baselines. This is done by simultaneously fitting the channels \nu_\mu \to \nu_\mu$, \bar\nu_e \to \bar\nu_\mu from \mu^- decays and the channels \bar\nu_\mu \to \bar\nu_\mu, \nu_e \to \nu_\mu from \mu^+ decays. We investigate the sensitivity reach in the parameter \sin^22\theta_{13} to which one can determine the sign of \delta m_{32}^2 to 3 standard deviations as a function of the baseline length and magnitude of \delta m_{32}^2 with a 20 GeV muon storage ring. We find that for baselines longer than 2000 km, the sign of \delta m^2_{32} can be determined for \sin^22\theta_{13} down to the 10^{-3} level with 10^{20} decays of 20 GeV muons.