Matter effects in neutrino visible decay at future long-baseline experiments

Neutrino visible decay in the presence of matter is re-evaluated. We study these effects in two future long-baseline experiments where matter effects are relevant: DUNE (1300 km) and a hypothetical beam aimed towards ANDES (7650 km). We find that matter effects are negligible for the visible component of neutrino decay at DUNE, being much more relevant at ANDES. We perform a detailed simulation of DUNE, considering $\nu_\mu$ disappearance and $\nu_e$ appearance channels, for both FHC and RHC modes. The sensitivity to the decay constant $\alpha_3$ can be as low as $2\times10^{-6}$ eV$^2$ at 90% C.L., depending on the neutrino masses and type of coupling. We also show the impact of neutrino decay in the determination of $\theta_{23}$ and $\delta_{\rm CP}$, and find that the best-fit value of $\theta_{23}$ can move from a true value at the lower octant towards the higher octant.