Determining see-saw parameters from weak scale measurements?

The see-saw mechanism is a very attractive explanation for small neutrino masses, parametrized at the GUT scale by the right-handed Majorana mass matrix, M, and the neutrino Yukawa matrix, Y_ν. We show that in a SUSY model with universal soft terms, M and Y_ν can be calculated from the light neutrino masses, the MNS matrix, and Y_ν^†Y_ν, which enters into the left-handed slepton radiative corrections. This suggests that in principle the GUT-scale inputs of the seesaw could be reconstructed from the neutrino and sneutrino mass matrices. We briefly discuss why this is impractical, but advocate the neutrino and sneutrino mass matrices as an alternative bottom-up parametrization of the seesaw.