[1] Katholieke Univ Leuven, Leuven Grav Inst, Dept Mech Engn, Celestijnenlaan 200D Box 2415, B-3001 Leuven, Belgium
[2] Katholieke Univ Leuven, Dept Phys & Astron, Lab Semicond Phys, B-3001 Leuven, Belgium
[3] Univ Pisa, Dipartimento Fis E Fermi, I-56127 Pisa, Italy
[4] Chinese Univ Hong Kong, Dept Phys, Shatin, Hong Kong, New Territories, Peoples R China
[5] Katholieke Univ Leuven, STADIUS Ctr Dynam Syst Signal Proc & Data Analyt, Dept Elect Engn ESAT, B-3001 Leuven, Belgium
[6] Nikhef, Sci Pk 105, NL-1098 XG Amsterdam, Netherlands
[7] Univ Utrecht, Inst Gravitat & Subatom Phys GRASP, Princetonpl 1, NL-3584 CC Utrecht, Netherlands
[8] INFN, Sez Pisa, I-56127 Pisa, Italy