Solvable models for the gamma deformation having X(5) as limiting   symmetry. Removing some drawbacks of the existent descriptions
  Two solvable Hamiltonians for describing the dynamic gamma deformation, are proposed. The limiting case of each of them is the X(5) Hamiltonian. Analytical solutions for both energies and wave functions, which are periodic in $\gamma$, are presented in terms of spheroidal and Mathieu functions, respectively. Moreover, the gamma depending factors of the transition operator can be treated. 
A. C.Gheorghe, A. A. Raduta and Amand Faessler