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Probing non-standard neutrino interactions with neutrino factories

Abstract:

We discuss the sensitivity reach of a neutrino factory measurement to non-standard neutrino interactions (NSI), which may exist as a low-energy manifestation of physics beyond the Standard Model. We use the muon appearance modes ν eν μ/ eμ and consider two detectors, one at L = 3000 km and the other at L = 7000 km; The latter is nearly at the magic baseline which is known to have a great sensitivity to matter density determination. Assuming the effects of NSI at the production and the detection are negligible, we discuss the sensitivities to NSI and the simultaneous determination of θ 13 and δ by examining the effects in the neutrino propagation of various systems in which two NSI parameters αβ are switched on. The sensitivities to off-diagonal 's are found to be excellent up to small values of θ 13. At sin 22θ 13 = 10 -4, for example, | eτ| a few × 10 -3 at 3σ CL for 2 degrees of freedom, whereas the ones for the diagonal 's are also acceptable, | ee|(| ττ|) 0.1(0.2) at the same CL. We demonstrate that the two-detector setting is powerful enough to resolve the θ 13-NSI confusion problem, a notorious one which is thought to be an obstacle in determining θ 13 and δ. We believe that the results obtained in this paper open the door to the possibility of using neutrino factory as a discovery machine for NSI while keeping its primary function of performing precision measurements of the lepton mixing parameters. © SISSA 2007.