Physics Theory Seminar with Srubabati Goswami on The Fable of the Unstable Neutrinos

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.

This lecture was made possible by the William C. Ferguson fund.