1. Max-Planck-Institute for Nuclear Physics, Saupfercheckweg 1, 69117 Heidelberg, Baden-Württemberg, Germany
2. Paul Scherrer Institut, Forschungsstrasse 111, 5232 Villigen, Switzerland
3. Department of Physics and Astronomy, Ruprecht-Karls University, 69120 Heidelberg, Baden-Württemberg, Germany