1. Department de Physique de la Matière Condensée, Université de Genève, Genève 1211, Switzerland
2. Swiss Light Source, Paul Scherrer Institute, CH-5232 Villigen, Switzerland
3. Canadian Light Source, Saskatoon, Saskatchewan S7N 2V3, Canada
4. Service de Physique de l’Etat Condensé (CNRS URA 2464), CEA Saclay, 91191 Gif-sur-Yvette, France
5. Centre de Physique Théorique (CPHT), École Polytechnique, Palaiseau, Cedex 91128, France
6. Department of Physics and Astronomy, University of British Columbia, Vancouver, British Columbia V6T 1Z1, Canada