Abstract
The scalar nonstandard interactions (NSI) can also introduce matter effect for neutrino oscillation in a medium. Especially the recent Borexino data prefer nonzero scalar NSI, η_{ee}=-0.16. In contrast to the conventional vector NSI, the scalar type contributes as a correction to the neutrino mass matrix rather than the matter potential. Consequently, the scalar matter effect is energy independent while the vector one scales linearly with neutrino energy. This leads to significantly different phenomenological consequences in reactor, solar, atmospheric, and accelerator neutrino oscillations. A synergy of different types of experiments, especially those with matter density variation, is necessary to identify the scalar NSI and guarantee the measurement of CP violation at accelerator experiments.
Highlights
In the very first paper [2] on the neutrino matter effect, Wolfenstein introducted nonstandard interactions with generally parametrized vector and axial-vector currents. This opens up the possibility of using neutrino oscillation to probe extra new physics beyond the standard model (SM), in addition to the neutrino mass matrix [6]
Coming back to the effect of nonstandard interactions (NSI) induced by ordinary matter on neutrino oscillations, the discussion so far has been focusing on vector currents, either from a vector mediator or with Fierz transformation from a charged scalar [13]
The same thing happens to the absolute mass scale that can be subtracted from MM† as a common m2i term but is always associated with the scalar NSI contribution as MδM† þ M†δM
Summary
The scalar nonstandard interactions (NSI) can introduce matter effect for neutrino oscillation in a medium. In the very first paper [2] on the neutrino matter effect, Wolfenstein introducted nonstandard interactions with generally parametrized vector and axial-vector currents This opens up the possibility of using neutrino oscillation to probe extra new physics beyond the standard model (SM), in addition to the neutrino mass matrix [6]. Coming back to the effect of NSI induced by ordinary matter on neutrino oscillations, the discussion so far has been focusing on vector currents, either from a vector mediator or with Fierz transformation from a charged scalar [13]. A natural mechanism for neutrinos to acquire masses is via coupling with a scalar that has nonzero vacuum expectation values The matter effect can arise from the scalar mediator in MaVaNs [14] and fuzzy dark matter [10] scenarios, its size is not proportional to the ordinary matter
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