The t contamination of the golden muon sample at the Neutrino Factory
We study the contribution of ne nt t m transitions to the wrong sign muon sample of the golden channel of the Neutrino Factory. Muons from tau decays are not really a background, since they contain information from the oscillation signal, and represent a small fraction of the sample. However, if not properly handled they introduce serious systematic error, in particular if the detector/analysis are sensitive to muons of low energy. This systematic effect is particularly troublesome for large th13 1deg and prevents the use of the Neutrino Factory as a precision facility for large th13. Such a systematic error disappears if the tau contribution to the golden muon sample is taken into account. The fact that the fluxes of the Neutrino Factory are exactly calculable permits the knowledge of the tau sample due to the ne nt oscillation. We then compute the contribution to the muon sample arising from this sample in terms of the apparent muon energy. This requires the computation of a migration matrix Mij which describes the contributions of the tau neutrinos of a given energy Ei, to the muon neutrinos of an apparent energy Ej. We demonstrate that applying Mij to the data permits the full correction of the otherwise intolerable systematic error.