# Sterile neutrinos at the CNGS

## TL;DR

This paper investigates the ability of the CNGS beam, especially the OPERA detector, to constrain sterile neutrino parameters, highlighting the importance of the
u_ au appearance channel and the impact of increased neutrino flux.

## Contribution

The study provides a detailed analysis of CNGS's potential to limit sterile neutrino models, emphasizing the
u_ au channel's significance and flux enhancement effects.

## Key findings

-
u_ au appearance channel offers the best constraint potential.
- Increased neutrino flux significantly improves sensitivity.
- Sterile neutrino constraints are robust for mq_ ext{Sbl}  0.1 eV^2.

## Abstract

We study the potential of the CNGS beam in constraining the parameter space of a model with one sterile neutrino separated from three active ones by an $\mathcal{O}(\eVq)$ mass-squared difference, $\Dmq_\Sbl$. We perform our analysis using the OPERA detector as a reference (our analysis can be upgraded including a detailed simulation of the ICARUS detector). We point out that the channel with the largest potential to constrain the sterile neutrino parameter space at the CNGS beam is $\nu_\mu \to \nu_\tau$. The reason for that is twofold: first, the active-sterile mixing angle that governs this oscillation is the less constrained by present experiments; second, this is the signal for which both OPERA and ICARUS have been designed, and thus benefits from an extremely low background. In our analysis we also took into account $\nu_\mu \to \nu_e$ oscillations. We find that the CNGS potential to look for sterile neutrinos is limited with nominal intensity of the beam, but it is significantly enhanced with a factor 2 to 10 increase in the neutrino flux. Data from both channels allow us, in this case, to constrain further the four-neutrino model parameter space. Our results hold for any value of $\Dmq_\Sbl \gtrsim 0.1 \eVq$, \textit{i.e.} when oscillations driven by this mass-squared difference are averaged. We have also checked that the bound on $\theta_{13}$ that can be put at the CNGS is not affected by the possible existence of sterile neutrinos.