Implications of lepton flavor violation on long baseline neutrino oscillation experiments

Nonstandard neutrino interactions (NSIs), the subleading effects in the flavor transitions of neutrinos, play a crucial role in the determination of the various unknowns in neutrino oscillations, such as neutrino mass hierarchy, the Dirac $CP$ violating phase, and the octant of the atmospheric mixing angle. In this work, we focus on the possible implications of lepton flavor violating (LFV) NSIs, which generally affect the neutrino propagation, on the determination of these unknown oscillation parameters. We study the effect of these NSIs on the physics potential of the currently running and upcoming long-baseline experiments, i.e., T2K, $\mathrm{NO}\nu \mathrm{A}$, and DUNE. We also check the allowed oscillation parameter space in the presence of LFV NSIs.

Figure 1

Neutrino appearance probability for the ${\nu }_{\mu }\to {\nu }_e$ without NSI (light shaded region) and with NSI (dark shaded green, red, and blue regions correspond to ${ϵ}_{e\mu }$, ${ϵ}_{\mu \tau }$, and ${ϵ}_{e\tau }$ parameter contributions, respectively) for T2K (top panel), $\mathrm{NO}\nu \mathrm{A}$ (middle panel), and DUNE (bottom panel). The hierarchy is assumed to be NH.

Figure 2

Neutrino appearance probability for the ${\nu }_{\mu }\to {\nu }_e$ without NSI (top panel) and with NSI (bottom panel) by assuming both NH (red) and IH (blue) for T2K (left panel), $\mathrm{NO}\nu \mathrm{A}$ (middle panel), and DUNE (right panel).

Figure 3

Mass hierarchy sensitivity as a function of true values of ${\delta }_{CP}$. The blue solid line in the figure corresponds to MH sensitivity without NSI, whereas the blue band in the figure shows the MH sensitivity in the presence of NSI (${ϵ}_{e\tau }=0.3$) in the allowed range of ${\delta }_{e\tau }$ for T2K (left panel), $\mathrm{NO}\nu \mathrm{A}$ (middle panel), and DUNE (right panel).

Figure 4

Neutrino appearance probability for the ${\nu }_{\mu }\to {\nu }_e$ without NSI (top panel) and with NSI (bottom panel) by assuming both HO (red) and LO (blue) for T2K (left panel), $\mathrm{NO}\nu \mathrm{A}$ (middle panel), and DUNE (right panel).

Figure 5

Octant sensitivity as a function of true values of ${\sin }^2{\theta }_{23}$. The blue line in the figure corresponds to the octant without NSI, whereas the light blue band in the figure shows the octant sensitivity in the presence of NSI (${ϵ}_{e\tau }=0.3$) in the allowed range of ${\delta }_{e\tau }$ for T2K (left panel), $\mathrm{NO}\nu \mathrm{A}$ (middle panel), and DUNE (right panel). Neutrino MH is assumed to be normal hierarchy.

Figure 6

The $CP$ asymmetry bands for T2K (left panel), $\mathrm{NO}\nu \mathrm{A}$ (middle panel), and DUNE (right panel) without NSI (light colored band) and with NSI (dark colored band) by assuming both NH (top panel) and IH (bottom panel). The solid black line corresponds to $CP$ asymmetry for ${\delta }_{CP}=0$ without NSI, whereas the dashed white line corresponds to $CP$ asymmetry for ${\delta }_{CP}=0$ with NSI (${ϵ}_{e\tau }=0.3$).

Figure 7

The CPV potential as a function of true values of ${\delta }_{CP}$ for T2K (left panel), $\mathrm{NO}\nu \mathrm{A}$ (middle panel), and DUNE (right panel) without NSI (solid blue line) and with NSI (band).

Figure 8

The $CP$ trajectory for T2K (left), $\mathrm{NO}\nu \mathrm{A}$ (middle) and DUNE (right) with (bottom panel) and without (top panel) NSIs.

Figure 9

The parameter degeneracy among the oscillation parameter in the ${\delta }_{CP}$-CP asymmetry plane for the DUNE experiment. The top left panel shows the degeneracies in SO, whereas the other three panels show the degeneracy in the presence of LFV-NSI with ${\delta }_{e\tau }=0$, $-90$, and 90, respectively. The bottom panel shows the $A_{CP}$ for NH-HO, NH-LO, IH-LO, and IH-LO in the presence of NSI (${ϵ}_{e\tau }=0.3$ and ${\delta }_{e\tau }=[\pi :\pi ]$).

Figure 10

The $2\sigma$ C.L. regions for ${\sin }^2{\theta }_{23}$ vs ${\delta }_{CP}$ with true ${\sin }^2{\theta }_{23}=0.41$ (0.59) for LO (HO) and true ${\delta }_{CP}=-90°$. The top panel corresponds to T2K and the bottom panel corresponds to the DUNE experiments.