This award will provide support for operations on two experimental initiatives in particle astrophysics: solar neutrinos with the Borexino liquid scintillator detector and dark matter with the DarkSide-50 liquid argon Time Projection Chamber (TPC). The nascent dark matter project will take advantage of the expertise in and facilities for low background methods accumulated by the Borexino collaboration in over two decades of research. DarkSide-50 will take advantage of the Borexino Counting Test Facility (CTF) and of the scintillator and water purification equipment built at the underground lab at Gran Sasso, Italy by the Borexino collaboration. While the Borexino and DarkSide collaborations remain two separate entities, almost all of the Borexino groups have joined the DarkSide Collaboration, and will work on both activities.
Borexino is a detector designed to observe low-energy solar neutrinos. It is the most recent large-scale, real-time solar neutrino detector to become operational and has been in operation for a little more than three years, during which time it has acquired solar and terrestrial neutrino data. The solar neutrino goal is to improve the measurement of Beryllium-7 neutrinos to an uncertainty less than 5%, and to make the first real time measurements of other neutrino branches, especially the pep, and possibly also the pp and CNO neutrinos. DarkSide-50 is a 50-kg dual-phase argon detector under development for the direct detection of dark matter particles. It is designed to test innovative low background methods to ensure background-free operation. It will initiate the use of underground argon for dark matter applications. It will be deployed, enclosed in a liquid scintillator neutron veto, within the CTF water tank. The scintillator-water combined shield provides background-free operation for ton-year exposures.
For Broader Impacts, the proposed activity will advance the scientific and educational mission in a variety of ways: (1) it will offer an excellent opportunity for the training of students, who will have a chance to contribute to the success of a cutting edge project in fundamental science and advanced engineering; (2) it will benefit society by developing techniques that could find application in areas ranging from national security to medical imaging; and (3) it will support continued development of successful E&O programs such as the Princeton-Abruzzo-South Dakota summer school for high school students.
