Decoherence, matter effect, and neutrino hierarchy signature in long baseline experiments

Environmental decoherence of oscillating neutrinos of strength Γ=(2.3±1.1)×10^-23 GeV can explain how maximal θ₂₃ mixing observed at 295 km by T2K appears to be nonmaximal at longer baselines. As shown recently by R. Oliveira, the Mikheyev-Smirnov-Wolfenstein matter effect for neutrinos is altered by decoherence: in normal (inverted) mass hierarchy, a resonant enhancement of ν_μ(ν_μ)→νₑ(νₑ) occurs for 6<E_ν<20 GeV. Thus decoherence at the rated strength may be detectable as an excess of charged-current νₑ events in the full ν_μ exposures of MINOS+ and OPERA.