[1] Ist Nazl Fis Nucl, Sez Bologna, Bologna, Italy
[2] Inst Theoret & Expt Phys, Moscow 117259, Russia
[3] Joint Inst Nucl Res, Theoret Phys Lab, Dubna 141980, Moscow Reg, Russia
[4] Moscow Inst Phys & Technol, Dolgoprudnyi 141700, Moscow Reg, Russia
[5] CNRS, Lab Phys Theor LAPTH, F-74941 Annecy Le Vieux, France
[6] Univ Savoie, F-74941 Annecy Le Vieux, France