Probing Non-standard Neutrino Physics at Neutrino Factory and T2kk

We discuss ways to explore non-standard interactions (NSI) which neutrinos may possess by expressing them as effective four Fermi operators with coefficient of the order of (MW /MNP ) 2 ∼ 10(10) for energy scales of new physics as MNP ∼ 1(10) TeV. Neutrino Factory is a prime candidate for such apparatus that can reach to the extreme precision. I describe a two detector setting, one at baseline L ∼ 3000 km and the other at L ∼ 7000 km, which is able to solve the notorious θ13−NSI confusion, and possibly also the two-phase confusion. The resultant sensitivities to off-diagonal NSI elements ε’s are excellent, |εeτ | ≃ a few × 10 and |εeμ| ≃ a few × 10. Our results suggest a new picture of neutrino factory as a hunting machine for NSI while keeping its potential of precision measurement of lepton mixing parameters. Sensitivities to NSI by T2KK and the related settings are also discussed.