1. Department of Physics, University of California, Berkeley, California 94720, USA
2. SLAC National Accelerator Laboratory/Kavli Institute for Particle Astrophysics and Cosmology, Menlo Park, California 94025, USA
3. Department of Physics, University of Colorado Denver, Denver, Colorado 80217, USA
4. Department of Electrical Engineering, University of Colorado Denver, Denver, Colorado 80217, USA
5. Fermi National Accelerator Laboratory, Batavia, Illinois 60510, USA
6. Kavli Institute for Cosmological Physics, University of Chicago, Chicago, Illinois 60637, USA
7. Department of Physics and Astronomy, and the Mitchell Institute for Fundamental Physics and Astronomy, Texas A&M University, College Station, Texas 77843, USA