Determination of the pattern of neutrino masses at a neutrino factory

Abstract

We study the precision with which the sign of δm 32 2 can be determined at a neutrino factory, as a function of stored muon energies and baselines. This is done by simultaneously fitting the channels ν μ → ν μ , ν ̄ e→ ν ̄ μ from μ − decays and the channels ν ̄ μ→ ν ̄ μ , ν e → ν μ from μ + decays. For a 20 GeV muon storage ring we investigate as a function of the baseline length and the magnitude of δm 32 2, the minimum value of the parameter sin 22 θ 13 for which the sign of δm 32 2 can be determined to at least 3 standard deviations. We find that for baselines longer than ∼3000 km, the sign of δm 2 32 can be determined for sin 22 θ 13 down to the 10 −3 level with 10 20 decays of 20 GeV muons.