Abstract
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.
Highlights
Neutrinos are notoriously elusive particles with an extremely low interaction rate [1], which oscillate among three different flavors [2,3,4,5,6,7,8,9]
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
Summary
Neutrinos are notoriously elusive particles with an extremely low interaction rate [1], which oscillate among three different flavors [2,3,4,5,6,7,8,9]. The unitary evolution driven by the effective potentials Vα(x) always preserves the purity of neutrino states While this is reasonable for neutrino oscillations in a low-density medium, for the interactions in a denser one, a loss of coherence due to collisions with the particles in the medium is to be expected. We show how the purity of the neutrino state is degraded as an effect of its interactions with the environment that can be interpreted as the quantum decoherence arising from a dissipative Markovian evolution This provides a microscopic qualitative and quantitative explanation to the phenomenology of decoherent neutrino oscillations as analyzed in previous works.
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