Solving the octant degeneracy with the Silver channel

TL;DR

This paper investigates how combining golden and silver neutrino detection channels at future neutrino factories can resolve the octant degeneracy in measuring neutrino mixing angles, using different detector technologies.

Contribution

It demonstrates that upgraded ECC and LAr TPC detectors can effectively resolve the octant degeneracy and detect deviations from maximal mixing with specific sensitivities.

Findings

ECC and LAr TPC detectors have comparable sensitivities.

Can discriminate solutions for sin^2(2θ13) ≥ 10^{-3}.

Able to detect deviations from maximal mixing of 4-6%.

Abstract

We study the potential of the combination of the golden ($\nu_e \to \nu_\mu$) and silver ($\nu_e \to \nu_\tau$) channels to solve the octant degeneracy affecting the measurement of $\theta_{13}$ and $\delta$ at future neutrino factories. To search for $\tau$ leptons produced in $\nu_\tau$ charged-current interactions, we consider two different detectors: the Emulsion Cloud Chamber detector (ECC) and the Liquid Argon Time Projection Chamber (LAr TPC). We show that, when using similar detector masses, the upgraded version of the ECC detector (sensitive also to hadronic $\tau$ decay modes) and the LAr TPC detector have comparable sensitivities to the octant of $\theta_{23}$, being able to discriminate the two solutions for $\sin^2 (2\theta_{13}) \gtrsim 10^{-3}$ at 3$\sigma$ level if $\theta_{23}=40^\circ$. We also show that the same setups are able to see deviation from maximal mixing as small as $\sim$ (4-6)% (at 3$\sigma$) if $\theta_{13}$ is close to its upper bound.