Exactly solvable pairing Hamiltonian for heavy nuclei
  We present a new exactly solvable Hamiltonian with a separable pairing interaction and non-degenerate single-particle energies. It is derived from the hyperbolic family of Richardson-Gaudin models and possesses two free parameters, one related to an interaction cutoff and the other to the pairing strength. These two parameters can be adjusted to give an excellent reproduction of Gogny self-consistent mean-field calculations in the canonical basis. 
J. Dukelsky, S. Lerma H., L. M. Robledo, R. Rodriguez-Guzman and S. M.   A. Rombouts
nucl-th