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

Abstract

Environmental decoherence of oscillating neutrinos of strength $\Gamma = (2.3 \pm 1.1) \times 10^{-23}$ GeV can explain how maximal $\theta_{23}$ mixing observed at 295 km by T2K appears to be non-maximal at longer baselines. As shown recently by R. Oliveira, the MSW matter effect for neutrinos is altered by decoherence: In normal (inverted) mass hierarchy, a resonant enhancement of $\nu_{\mu} (\bar{\nu}_{\mu}) \rightarrow \nu_{e} (\bar{\nu}_{e})$ occurs for $6 < E_{\nu} < 20$ GeV. Thus decoherence at the rated strength may be detectable as an excess of charged-current $\nu_{e}$ events in the full $\nu_{\mu}$ exposures of MINOS+ and OPERA.