Resolving CP violation by standard and nonstandard interactions and parameter degeneracy in neutrino oscillations

Abstract

In neutrino oscillation with non-standard interactions (NSI) the system is enriched with CP violation caused by phases due to NSI in addition to the standard lepton Kobayashi-Maskawa phase δ. In this paper we show that it is possible to disentangle the two CP violating effects by measurement of muon neutrino appearance by a near-far two detector setting in neutrino factory experiments. Prior to the quantitative analysis we investigate in detail the various features of the neutrino oscillations with NSI, but under the assumption that only one of the NSI elements, ε eµ or ε eτ , is present. They include synergy between the near and the far detectors, the characteristic differences between the ε eµ and ε eτ systems, and in particular, the parameter degeneracy. Finally, we use a concrete setting with the muon energy of 50 GeV and magnetized iron detectors at two baselines, one at L = 3000 km and the other at L = 7000 km, each having a fiducial mass of 50 kton to study the discovery potential of NSI and its CP violation effects. We demonstrate, by assuming 4 × 10 21 useful muon decays for both polarities, that one can identify non-standard CP violation down to |ε eµ | ≃ a few × 10 −3 , and |ε eτ | ≃ 10 −2 at 3σ CL for θ 13 down to sin 2 2θ 13 = 10 −4 in most of the region of δ. The impact of the existence of NSI on the measurement of δ and the mass hierarchy is also worked out.

Non standard neutrino interactions: current status and future prospects

“…Even if there is no mixing in vacuum, the flavor transitions n n  a b can occur in matter due to the presence of the off-diagonal NSI [18][19][20]. The complex phases of the off-diagonal elements e ab could be a new source of CP violation, see e.g., [31,64].…”

Constraints on the Nonstandard Interaction in Propagation from Atmospheric Neutrinos

“…As for the future long-baseline experiments, the sensitivity of the INO experiment was discussed in [44], that of the reactor and superbeam experiments was discussed in [45], that of the T2KK experiment was studied in [28,46], and that of the LBNE experiment was discussed in [43,47]. The sensitivity of neutrino factories [6] was studied in various contexts: the sensitivity to NSI [48][49][50], the confusion with the effect of 13 [51], the optimization [52], resolving degeneracy with two baselines [53,54], and the relation with nonunitary mixing [55].…”

Search for Nonstandard Neutrino Interactions with IceCube DeepCore

“…To date, no evidence has been observed [5,6]. In this paper, we address these predictions through a complementary search in the neutrino sector, seeking evidence for new flavor-changing neutrino interactions produced by TeV-scale bosons [7][8][9][10][11][12].…”