Beyond the MSW effect: Neutrinos in a dense medium

We present a theory of neutrino oscillations in a dense medium which goes beyond the effective matter potential used in the description of the MSW effect. We show how the purity of the neutrino state is degraded by neutrino interactions with the environment and how neutrino-matter interactions can be a source of decoherence. We present new oscillation formulae for neutrinos interacting with leptons and carry out a numerical analysis which exhibits deviations from the MSW formulae for propagation through the Earth of ultra-high energy neutrinos. In particular, we show that at high density and/or high neutrino energy, the vanishing transition probabilities derived for MSW effect, are non zero when the scattering is taken into account. (C) 2021 The Author(s). Published by Elsevier B.V.

Automated summary

This study presents a new theory of neutrino oscillations in a dense medium that goes beyond the traditional description of the MSW effect. The research demonstrates how interactions with the environment degrade the purity of neutrino states and how neutrino-matter interactions can result in decoherence. New oscillation formulas for neutrinos interacting with leptons are introduced, and numerical analysis shows deviations from the MSW formulas for ultra-high energy neutrinos propagating through the Earth, particularly at high density and/or high neutrino energy.