Reactor and atmospheric neutrino mixing angles’ correlation as a probe for new physics

We perform a simulation on the DUNE experiment to probe the capability of future neutrino long-baseline experiments to constrain the parameter space of high-energy models by using the correlation between the atmospheric and reactor mixing angles. As an example, we analyze the tetrahedral flavor symmetry model, which predicts a strong relation between the nonzero value of ${\theta }_{13}$ and a deviation of ${\theta }_{23}$ from maximality. We show that in this case, the model can realistically be excluded by more than $3\sigma$ for most of the parameter space. We also study the octant degeneracy at DUNE and its impact on the sensitivity of such models.

Figure 1

${\chi }^2$ as a function of the test value of ${\theta }_{13}$. The blue curve represents the standard paradigm, while the black curves are the prediction by the tetrahedral model: the continuous line corresponds to the lower octant, while the dashed line corresponds to the higher octant. In this analysis the true value considered for the atmospheric angle is ${\sin }^2{\theta }_{23}=0.43$.

Figure 2

Expected DUNE capability of probing the model at different confidence levels as a function of the true value of ${\theta }_{23}$ and ${\theta }_{13}$. The bands correspond to the 1 to $5\sigma$ C.L., while the black dashed curve represents the model prediction. The dashed (dot-dashed) line corresponds to the current global fit 90% (99%) C.L. [14] and the star corresponds to the best fit.

Figure 3

Projected precision measurement of ${\sin }^2{\theta }_{13}$ by the DUNE experiment: the one-dimensional ${\chi }^2$ projection of ${\theta }_{13}$ (left) and the ${\theta }_{23}$ and ${\theta }_{13}$ correlation (right). The colors represent the different confidence levels and the purple line is the model prediction.

Figure 4

Projected DUNE experiment confidence-level exclusion for the ${\sin }^2{\theta }_{13}(\mathrm{TRUE})\text{−}{\sin }^2{\theta }_{13}(\mathrm{TEST})$ plane.

Figure 5

DUNE capability of excluding any relation between ${\theta }_{13}$ and ${\theta }_{23}$ that follows Eq. (1). The colored curves represent 1 to $5\sigma$ C.L. and the dashed black curve is the tetrahedral model.

Figure 6

$3\sigma$ parameter space of Eq. (4) in the ${\theta }_{13}^0\text{−}f$ plane that cannot be distinguished from the unconstrained relation hypothesis by DUNE. The true values are ${\sin }^2{\theta }_{13}(\mathrm{TRUE})=0.02155$ and the three cases 1) ${\sin }^2{\theta }_{23}(\mathrm{TRUE})=0.43$ (green), 2) ${\sin }^2{\theta }_{23}(\mathrm{TRUE})=0.5$ (blue), and 3) ${\sin }^2{\theta }_{23}(\mathrm{TRUE})=0.6$ (red).