[1] Max Planck Inst Kernphys, D-69029 Heidelberg, Germany
[2] Max Planck Inst Phys & Astrophys, D-80805 Munich, Germany
[3] Univ Complutense, Fac Ciencias Fis, E-28040 Madrid, Spain
[4] Univ Hamburg, Inst Expt Phys, D-22761 Hamburg, Germany
[5] Univ Kiel, Inst Expt & Angew Phys, D-24118 Kiel, Germany
[6] Univ Wuppetal, Fachbereich Phys, D-42097 Wuppertal, Germany
[7] Yerevan Phys Inst, Yerevan 375036, Armenia
[8] Altai State Univ, Barnaul 656099, Russia