1. SNOLAB, Lively, Ontario P3Y 1N2, Canada and Department of Physics, Laurentian University, Sudbury, Ontario P3E 2C6, Canada;
2. Department of Physics, Queen's University at Kingston, Kingston, Ontario K7L 3N6, Canada;
3. Department of Physics, Carleton University, Ottawa, Ontario K1S 5B6, Canada and TRIUMF, Vancouver, British Columbia V6T 2A3, Canada;