Abstract
In this article we unravel the role of matter effect in neutrino oscillation in the presence of lepton-flavor-conserving, non-universal non-standard interactions (NSI's) of the neutrino. Employing the Jacobi method, we derive approximate analytical expressions for the effective mass-squared differences and mixing angles in matter. It is shown that, within the effective mixing matrix, the Standard Model (SM) W-exchange interaction only affects $\theta_{12}$ and $\theta_{13}$, while the flavor-diagonal NSI's only affect $\theta_{23}$. The CP-violating phase $\delta$ remains unaffected. Using our simple and compact analytical approximation, we study the impact of the flavor-diagonal NSI's on the neutrino oscillation probabilities for various appearance and disappearance channels. At higher energies and longer baselines, it is found that the impact of the NSI's can be significant in the numu to numu channel, which can probed in future atmospheric neutrino experiments, if the NSI's are of the order of their current upper bounds. Our analysis also enables us to explore the possible degeneracy between the octant of $\theta_{23}$ and the sign of the NSI parameter for a given choice of mass hierarchy in a simple manner.
Highlights
The running of the effective mass-squared differences are modified in the range β 0
In previous papers [68, 70], we showed that the neutrino oscillation probabilities in matter can be well understood if we allow the mixing angles and mass-squared diffe√rences in the standard parametrization to ‘run’ with the matter effect parameter a = 2 2GF NeE, where Ne is the electron density in matter and E is the neutrino energy
We found that for large θ13, the entire matter effect could be absorbed into the running of the effective mass-squared differences and the effective mixing angles θ12 and θ13, while neglecting the running of the mixing angle θ23 and the CP-violating phase δ
Summary
The recent measurement of the moderately large value of the 1-3 mixing angle [1,2,3,4,5,6,7,8,9,10,11], quite close to its previous upper limit [12, 13], strongly validates the standard three-flavor oscillation model of neutrinos [14, 15], which has been quite successful in explaining all the neutrino oscillation data available so far [16,17,18], except for a few anomalies observed at very-short-baseline experiments [19]. To obtain similar insights for the NSI case, approximate analytical expressions for the three-flavor oscillation probabilities in constant-density matter in the presence of NSI’s are called for. Once they have provided us with the intuition we seek, on how and why the oscillation probabilities behave in a particular way, we can resort to numerical techniques to further refine the analysis, e.g. taking into account the non-constant mass-density, if the need arises. We will show how the presence of such flavor-diagonal NSI’s affect the running of the effective neutrino oscillation parameters (the mass-squared differences, mixing angles, and CP-violating phase), and how they alter the oscillation probabilities. In appendix B, we examine the differences in the exact numerical probabilities with line-averaged constant Earth density and varying Earth density profile for 8770 km and 10000 km baselines
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
