Grant: Subatomic Physics Envelope - Project

It is well-established that most of the matter in our universe is dark; more than three quarters of all mattercurrently evades direct observation. The origin and nature of this dark matter is currently one of the mostimportant questions in particle astrophysics, evidenced by the active global research effort aimed at dark matter detection. A favored hypothesis is that the dark matter consists of WIMPs, weakly interacting massiveparticles, which could be detected by observing their elastic scattering from nuclei. This proposal will enablethe completion and first analysis of the DEAP-3600 experiment at SNOLAB for a very sensitive dark mattersearch. Unique to DEAP-3600 is the novel technique of discriminating background events using the timeevolution of the scintillation pulse, which leads to a simple detector design that can be scaled to a very largetarget mass. Operation at the deep underground SNOLAB facility allows extremely low backgrounds whichwould otherwise mask dark matter signals. DEAP-3600 will increase sensitivity to dark matter particles by afactor of 50, allowing tests of theoretical models that predict dark matter detection is possible. Theproject is currently being installed in the SNOLAB Cube Hall. The central detector consists of a large (85 cm radius) acrylic vessel which contains the 3600 kg cryogenic liquid argon and is viewed by 255 photomultiplier tubes to detect argon scintillation light pulses from nuclear recoils. The experiment will be housed in an 8 meter diameter water shielding tank and supported by a deck structure, both of which have been completed at SNOLAB. Installation of the detector subsystems (acrylic vessel, argon purification equipment, readout electronics and trigger, and associated infrastructure) is expected to continue until the end of 2013, after which the detector will be filled and prepared for data collection. This proposal will lead to further training of highly qualified personnel in Canada. In addition to attracting students and international highly qualified researchers, it is anticipated that the post-doctoral fellows, RAs, and students supported by this request will have the opportunity to take part in this leading-edge science.