[1] Univ Nacl Autonoma Mexico, Inst Ciencias Nucl, Mexico City 04510, DF, Mexico
[2] Yale Univ, Sloane Phys Lab, Ctr Theoret Phys, New Haven, CT 06520 USA
[3] CEA DSM, CNRS, IN2P3, Grand Accelerateur Natl Ions Lourds, F-14076 Caen 5, France
[4] Univ Nacl Autonoma Mexico, Fac Ciencia, Mexico City 04510, DF, Mexico