CP-violation in 3- and 4-family at the Neutrino Factory

The leptonic CP-violating phase $\delta$ can be measured with a Neutrino Factory with $2 \times 10^{20} $ useful muons per year, if the solar neutrino problem is solved by the LMA-MSW solution, with $\Delta m_{12}^2 \ge 2 \times 10^{-5}$ eV$^2$ (in this analysis a 40 kT magnetized iron detector is considered, taking into account its efficiencies and backgrounds). If LSND is confirmed, CP-violating phenomena in four-family scenarios can be most easily addressed with a small 1 kT detector at $L = \cal O$(10) km (no detailed analysis of the detector efficiencies and backgrounds has been performed in this case).