Analytic treatment of neutrino oscillation and decay in matter

by Srubabati Goswami (Physical Research Laboratory Ahmedabad)

HS2 (Physikdepartment)




Neutrino decay is governed by a non-Hermitian effective Hamiltonian and in general the mass eigenstates and decay eigenstates are not the same. This mismatch is inevitable in the presence of matter and the Hermitian and anti-Hermitian components cannot be simultaneously diagonalized by unitary transformations for all matter densities. In this talk a formalism for treating the two-flavor neutrino propagation through matter of uniform density, for neutrino decay to invisible states, will be discussed. First, it will be shown how employing the inverse Baker-Campbell-Hausdorff or Zassenhaus expansion, compact analytic expressions for neutrino survival and conversion probabilities can be obtained. We will also discuss the approximate analytic probabilities in the three generation framework and show the baselines and energies where the different approximations give good matching with the numerical probabilities. These results provide physical insights into the effects of neutrino decay at long-baseline neutrino oscillation experiments.