As the two phenomena nonstandard interaction (NSI) in neutrino propagation and Lorentz invariance violation (LIV) modify the Hamiltonian of neutrino oscillation in a similar fashion, it is very difficult to distinguish these two effects. The only difference between them lies in the fact that NSI depends on the matter density, whereas LIV is independent of the earth matter effect. Therefore for a fixed baseline experiment, where matter density is constant, the theories describing NSI and LIV are exactly equivalent. However, as the present and future bounds of the NSI and LIV parameters are not equivalent, one can distinguish these two scenarios in the long-baseline neutrino experiments depending on their statistics with respect to the present and future bounds of these parameters. In this paper, we attempt to differentiate between LIV and NSI in the context of DUNE and P2SO, as these two future experiments are believed to be sensitive to the strongest matter effect and will have very large statistics. Taking LIV in the data and NSI in theory, our results show that indeed it is possible to have good discrimination between LIV and NSI. The best separation between LIV and NSI at $3\sigma \mathrm{C}.\mathrm{L}.$ is achieved for the parameter $a_{\mu \mu }$ with P2SO. In this case, the value of the LIV parameter, for which separation is possible, lies within its future bound if one considers the value of NSI parameter to be constrained by the present experiments. Between DUNE and P2SO, the latter has better sensitivity for such discrimination.

Neutrinos are the fundamental particles, blind to all kind of interactions except the weak and gravitational. Hence, they can propagate very long distances without any deviation. This characteristic property can thus provide an ideal platform to investigate Planck suppressed physics through their long distance propagation. In this work, we intend to investigate CPT violation through Lorentz invariance violation (LIV) in the long-baseline accelerator based neutrino experiments. Considering the simplest four-dimensional Lorentz violating parameters, for the first time, we obtain the sensitivity limits on the LIV parameters from the currently running long-baseline experiments T2K and $$\hbox {NO}\nu \hbox {A}$$NOνA . In addition to this, we show their effects on mass hierarchy and CP violation sensitivities by considering $$\hbox {NO}\nu \hbox {A}$$NOνA as a case study. We find that the sensitivity limits on LIV parameters obtained from T2K are much weaker than that of $$\hbox {NO}\nu \hbox {A}$$NOνA and the synergy of T2K and $$\hbox {NO}\nu \hbox {A}$$NOνA can improve these sensitivities. All these limits are slightly weaker ( $$2 \sigma $$2σ level) compared to the values extracted from Super-Kamiokande experiment with atmospheric neutrinos. Moreover, we observe that the mass hierarchy and CPV sensitivities are either enhanced or deteriorated significantly in the presence of LIV as these sensitivities crucially depend on the new CP-violating phases. We also present the correlation between $$\sin ^2 \theta _{23}$$sin2θ23 and the LIV parameter $$|a_{\alpha \beta }|$$|aαβ| , as well as $$\delta _{CP}$$δCP and $$|a_{\alpha \beta }|$$|aαβ| .

In this paper, we study the capability of different long-baseline experiment options at the KM3NeT facility, i.e., P2O, upgraded P2O, and P2SO to probe the light sterile neutrino and compare their sensitivities with DUNE. The P2O option will have neutrinos from a 90 KW beam at Protvino to be detected at the ORCA detector, the upgraded P2O will have neutrinos from the upgraded 450 KW beam to be detected at the ORCA detector and the option P2SO will have neutrinos from a 450 KW beam to be detected at the upgraded Super-ORCA detector. All these options will have a baseline around 2595 km. Our results show that the experiments at the KM3NeT (DUNE) would be more sensitive if the value of $\mathrm{\Delta }{m}_{41}^2$ is around 10 (1) ${\mathrm{eV}}^2$. Our results also show that the role of near detector is very important for the study of sterile neutrinos and addition of near detector improves the sensitivity as compared to only the far detector for the $3+1$ scenario. Among the three options at KM3NeT, the sensitivity of P2O and upgraded P2O is limited and sensitivity of P2SO is either comparable or better than DUNE.

In this paper, we study the hierarchy sensitivity of Protvino to ORCA (P2O) experiment in three flavour scenario as well as its sensitivity to non-standard interactions (NSI) in neutrino propagation. Because of the largest possible baseline length of 2595 km, P2O is expected to have strong sensitivity towards neutrino mass hierarchy and NSI parameters. In our study, we show that even though the number of appearance channel events for the minimal configuration of P2O are higher compared to DUNE, still the hierarchy sensitivity of P2O is less than DUNE because of large background events. Our results show that for a background reduction factor of 0.46 and appearance channel background systematic normalization error of 4%, the hierarchy sensitivity of P2O becomes equivalent of DUNE for δ_CP = 195°. We call this configuration of P2O as optimized P2O. Regarding the study of NSI, we find that, for ϵ_eμ (ϵ_eτ) sensitivity of DUNE is similar (better) as compared to optimized P2O when both ϵ_eμ and ϵ_eτ are included in the analysis. Our results show that in presence of NSI, the change of hierarchy sensitivity with respect to standard three flavor scenario, is higher in P2O as compared to DUNE. Further, hierarchy sensitivity in presence of NSI is lower (higher) than sensitivity in the standard three flavour scenario for δ_CP = 270°(90°). It is important to note that hierarchy sensitivity of optimized P2O does not get significantly better than DUNE for the current favourable values of δ_CP which is 180° < δ_CP< 360° as obtained by the global analysis in both standard three flavour and in presence of NSI.

In this paper we have studied the phenomenon of nonstandard interaction mediated by a scalar field (SNSI) in the context of P2SO experiment and compared its sensitivity with DUNE. In particular, we have studied the capability of these two experiments to put bounds on the diagonal SNSI parameters, i.e., ${\eta }_{ee}$, ${\eta }_{\mu \mu }$, and ${\eta }_{\tau \tau }$ and studied the impact of these parameters on the determination of neutrino mass ordering, octant of ${\theta }_{23}$ and $CP$ violation (CPV). In our analysis we find that, the parameter $\mathrm{\Delta }{m}_{31}^2$ has a nontrivial role if one wants estimate the bounds on ${\eta }_{\mu \mu }$ and ${\eta }_{\tau \tau }$ assuming SNSI does not exist in nature. Our results show that sensitivity of P2SO and DUNE to constraint ${\eta }_{\mu \mu }$ and ${\eta }_{\tau \tau }$ are similar whereas the sensitivity of DUNE is slightly better for ${\eta }_{ee}$. We find that the mass ordering and CPV sensitivities are mostly affected by ${\eta }_{ee}$ compared to ${\eta }_{\mu \mu }$ and ${\eta }_{\tau \tau }$ if one assumes SNSI exists in nature. On the other hand, octant sensitivity is mostly affected by ${\eta }_{\mu \mu }$ and ${\eta }_{\tau \tau }$. These sensitivities can be either higher or lower than the standard three flavor scenario depending on the relative sign of the SNSI parameters. Regarding the precision of atmospheric mixing parameters, we find that the precision of ${\theta }_{23}$ deteriorates significantly in the presence of ${\eta }_{\mu \mu }$ and ${\eta }_{\tau \tau }$.

Recent ν _e appearance data from the Mini Booster Neutrino Experiment support the excess of events reported by the Liquid Scintillator Neutrino Detector, which provides an indirect hint of the existence of eV-scale sterile neutrinos. As these sterile neutrinos can mix with the standard active neutrinos, in this paper we explore the effect of such active–sterile mixing on the determination of various oscillation parameters by the currently running long-baseline neutrino experiments T2K and NO ν A. We find that the existence of sterile neutrinos can lead to new kinds of degeneracies among these parameters which would substantially deteriorate the mass hierarchy sensitivity of the NO ν A experiment. We further notice that the inclusion of data from the T2K experiment helps in resolving the degeneracies. The impact of new CP-violating phases δ ₁₄ and δ ₃₄ on the maximal CP violation exclusion sensitivity for the NO ν A experiment has also been illustrated. Finally, we discuss the implication of such light sterile neutrinos on neutrinoless double-beta decay processes in line with recent experimental results, as well as on the sensitivity reach of future experiments.