The identification of dark matter is one of the major scientific challenges of our time. Weakly Interacting Massive Particles (WIMPs) are possible candidates. It is expected that the discovery and understanding of WIMP dark matter will require very large target masses. This award will support work on the MiniCLEAN detector, a single-phase detector designed to scale to large detector masses. MiniCLEAN follows the example of neutrino experiments where a monolithic target volume is surrounded by photomuliplier tubes, and the primary rejection of external backgrounds comes from the self-shielding made possible by the sheer size of the detector. This approach detects recoiling nuclei from WIMP interactions in liquid argon using only scintillation light. The simplicity of the single-phase technique allows for the construction of very large mass detectors at relatively low cost. The MiniCLEAN detector is presently under construction at SNOLAB. MIT has been involved in multiple aspects of the MiniCLEAN experiment, including the design and fabrication of muon veto system, the design and fabrication of the neutron calibration system, simulation and verification of the neutron background model, and preparation for data analysis. This award will support the MIT group's involvement in commissioning and operation of MiniCLEAN, and the subsequent data analysis.
Broader Impact: The MiniCLEAN experiment will provide training for students and postdocs. The MIT group actively participates in the MIT-sponsored Undergraduate Research Opportunities Program (UROP), which provides a forum for undergraduates to participate in experimental research.
The identification of dark matter constitutes one of the major scientific challenges of our time, a compelling explanation of which is the existence of Weakly Interacting Massive Particles (WIMPs). A number of experimental techniques have been developed to directly detect WIMPs by measuring combinations of scintillation light, ionization, or heat, using multiple handles to discriminate a WIMP signal from radioactive backgrounds. It is likely that the discovery and understanding of WIMP dark matter will ultimately require very large target masses, and the vision is therefore the eventual construction of a very large scale detector. To get to such large scales at reasonable cost, the collaboration follows the example of great neutrino experiments like KamLAND, SNO, and Super-Kamiokande, in which a monolithic target volume is surrounded by photomuliplier tubes (PMTs). The primary rejection of external backgrounds thus comes from the self-shielding made possible by the sheer size of the detector. The MiniCLEAN detector, presently under construction at SNOLAB, will serve as the technical demonstration of this approach and provide the first direct search for WIMP dark matter with this technology MIT has been involved in multiple aspects of the MiniCLEAN experiment, including the design and fabrication of muon veto system, the design and fabrication of the neutron calibration system, simulation and verification of the neutron background model, and preparation for data analysis. As a result of the support from this grant (and the previous grant cycle), MIT was able to provide on-site operations support for the commissioning of the experiment, as well as delivery of the muon veto system. MIT was able to participate in the initial data taking of the experiment (vacuum and argon gas phase) and provide a measurement of the alpha contamination of the vessel (an important background measurement needed for the final liquid argon run). This grant also allowed support of graduate and undergraduate student participation in experimental physics. We thank the NSF for their support in this important cutting edge research.
