Raman stimulated neutrino pair emission

A new scheme using macroscopic coherence is proposed to experimentally determine the neutrino mass matrix, in particular the absolute value of neutrino masses, and the mass type, Majorana or Dirac. The proposed process is a collective, coherent Raman scattering followed by neutrino-pair emission from | e⟩ of a long lifetime to | g⟩ ; γ+ | e⟩ → γ+ ∑ _ijν_iν_j¯ + | g⟩ with ν_iν_j¯ consisting of six massive neutrino-pairs. Calculated angular distribution has six (ij) thresholds which show up as steps at different angles. Angular locations of thresholds and event rates of the angular distribution make it possible to experimentally determine the smallest neutrino mass to the level of less than several meV, (accordingly all three masses using neutrino oscillation data), the mass ordering pattern, normal or inverted, and to distinguish whether neutrinos are of Majorana or Dirac type. Event rates of neutrino-pair emission, when the mechanism of macroscopic coherence amplification works, may become large enough for realistic experiments by carefully selecting certain types of target. The problem to be overcome is macro-coherently amplified quantum electrodynamic background of the process, γ+ | e⟩ → γ+ γ₂+ γ₃+ | g⟩ , when two extra photons, γ₂, γ₃, escape detection. We illustrate our idea using neutral Xe and trivalent Ho ion doped in dielectric crystals.