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 ν_μ disappearance and ν_e appearance channels, for both FHC and RHC modes. The sensitivity to the decay constant α₃ can be as low as 2 × 10 ^{- 6} eV² 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 θ₂₃ and δ_CP, and find that the best-fit value of θ₂₃ can move from a true value at the lower octant towards the higher octant.