Level spacing of U(5) \leftrightarrow SO(6) transitional region with   maximum likelihood estimation method
  In this paper,a systematic study of quantum phase transition within U(5) \leftrightarrow SO(6) limits is presented in terms of infinite dimensional Algebraic technique in the IBM framework. Energy level statistics are investigated with Maximum Likelihood Estimation (MLE) method in order to characterize transitional region. Eigenvalues of these systems are obtained by solving Bethe-Ansatz equations with least square fitting processes to experimental data to obtain constants of Hamiltonian. Our obtained results verify the dependence of Nearest Neighbor Spacing Distribution's (NNSD) parameter to control parameter (c_{s}) and also display chaotic behavior of transitional regions in comparing with both limits. In order to compare our results for two limits with both GUE and GOE ensembles, we have suggested a new NNSD distribution and have obtained better KLD distances for the new distribution in compared with others in both limits. Also in the case of N\to\infty, the total boson number dependence displays the universality behavior, namely NNSD tends to Poisson limit for every values of control parameter. 
M. A. Jafarizadeh, N. Fouladic, H. Sabric, B. Rashidian Malekic
nucl-th