Neutrino Factories: Detector Concepts for studies of CP and T violation effects in neutrino oscillations

The ideal neutrino detector at the neutrino factory should have a mass in the range of 10 kton, provide particle identification to tag the flavor of the incoming neutrino, lepton charge measurement to select the incoming neutrino helicity, good energy resolution to reconstruct the incoming neutrino energy, and be isotropic to equally well reconstruct incoming neutrinos from different baselines (it might be more efficient to build various sources at different baselines, than various detectors). The detector should also be able to reconstruct neutrino event typically below 15 GeV. A detector with such quality is most adapted to fully study neutrino oscillations at the neutrino factory. In particular, measurement of the leading muons and electrons charge is the only way to fully simultaneously explore CP and T violation effects. We think that a magnetized liquid argon imaging detector stands today as the best choice of technique, that holds the highest promises to match the above mentioned detector requirements. We discuss also the optimal neutrino factory energy and baseline between source and detector in order to best perform these studies.