Abstract
Current neutrino experiments are measuring the neutrino mixing parameters with an unprecedented accuracy. The upcoming generation of neutrino experiments will be sensitive to subdominant oscillation effects that can give information on the yet-unknown neutrino parameters: the Dirac CP-violating phase, the mass ordering and the octant of $\theta_{23}$. Determining the exact values of neutrino mass and mixing parameters is crucial to test neutrino models and flavor symmetries designed to predict these neutrino parameters. In the first part of this review, we summarize the current status of the neutrino oscillation parameter determination. We consider the most recent data from all solar experiments and the atmospheric data from Super-Kamiokande, IceCube and ANTARES. We also implement the data from the reactor neutrino experiments KamLAND, Daya Bay, RENO and Double Chooz as well as the long baseline neutrino data from MINOS, T2K and NOvA. If in addition to the standard interactions, neutrinos have subdominant yet-unknown Non-Standard Interactions (NSI) with matter fields, extracting the values of these parameters will suffer from new degeneracies and ambiguities. We review such effects and formulate the conditions on the NSI parameters under which the precision measurement of neutrino oscillation parameters can be distorted. Like standard weak interactions, the non-standard interaction can be categorized into two groups: Charged Current (CC) NSI and Neutral Current (NC) NSI. Our focus will be mainly on neutral current NSI because it is possible to build a class of models that give rise to sizeable NC NSI with discernible effects on neutrino oscillation. These models are based on new $U(1)$ gauge symmetry with a gauge boson of mass $\lesssim 10$~MeV. The UV complete model should be of course electroweak invariant which in general implies that along with neutrinos, charged fermions also acquire new interactions on which there are strong bounds. We enumerate the bounds that already exist on the electroweak symmetric models and demonstrate that it is possible to build viable models avoiding all these bounds. In the end, we review methods to test these models and suggest approaches to break the degeneracies in deriving neutrino mass parameters caused by NSI.
Highlights
In the framework of “old” electroweak theory, formulated by Glashow, Weinberg and Salam, lepton flavor is conserved and neutrinos are massless
For more details about the assumptions considered in each case, we refer the reader to the previous subsections as well as to the original references where the constraints have been calculated
Most of the limits have been derived from the combination of neutrino oscillation and detection or production experimental results
Summary
In the framework of “old” electroweak theory, formulated by Glashow, Weinberg and Salam, lepton flavor is conserved and neutrinos are massless. Solar neutrino anomaly (deficit of the solar neutrino flux relative to standard solar model predictions) [1] and atmospheric neutrino anomaly (deviation of the ratio of muon neutrino flux to the electron neutrino flux from 2 for atmospheric neutrinos that cross the Earth before reaching the detector) [2] were two main observations that showed the lepton flavor was violated in nature This conclusion was further confirmed by observation of flavor violation of man-made neutrinos after propagating sizable distances in various reactor [3,4,5] and long baseline experiments [6, 7]. Each component mass eigenstate acquires a different phase so neutrino of definite flavor will convert to a mixture of different flavors; lepton flavor violation takes place
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