DUSEL Research and Development on subKelvin germanium for ton scale dark matter search

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PROPOSAL NUMBER: 0705078INSTITUTION: University of California ? Berkeley NSF PROGRAM: PHY - PARTICLE ASTROPHYSICSPRINCIPAL INVESTIGATOR: Sadoulet, BernardTITLE: DUSEL Research and Development on subKelvin germanium for ton scale dark matter search ABSTRACTDeciphering the nature of dark matter in the universe is one of the most urgent tasks in cosmology and particle physics today, and a successful program to detect Weakly Interactive Massive Particles (WIMPs) critically depends on the performance of the instrumentation available. This proposal requests support to enable improved future experiments for the Deep Underground Science and Engineering Laboratory (DUSEL). This effort is directed at improving the position resolution and rejection capability of the phonon-mediated plus ionization detector technology, which currently reaches the best WIMP sensitivity, and therefore is likely to open new scientific opportunities for a ton scale dark matter experiment. The UC Berkeley group is a member of the SuperCDMS collaboration which will operate 25 kg of germanium sub-Kelvin detectors at the SNOLAB underground laboratory, aiming to reach a sensitivity approaching 10^(−45) cm^2 for spin independent cross sections and WIMP masses near 60 GeV. Such a sensitivity reach is scientifically very important and explores much of the same parameter space as the Large Hadron Collider for supersymmetric dark matter in the form of the lightest supersymmetric particle. The DUSEL facility may be ready for experiments as early as 2012 or 2013 and it will be scientifically important to build at least one ton-scale dark matter experiment to improve further the sensitivity for WIMPs. It is natural to select the best one or two technologies around 2009-2010, most likely the sub-Kelvin and noble liquid strategies. For the sub-Kelvin technology, there is a need to improve background rejection and to develop mass production techniques to reduce costs and increase fabrication yields. In this three-year proposal, support is requested for one postdoctoral fellow and one undergraduate. This modest level of support will allow the group to fabricate and test several detector designs. The CDMS team has been at the forefront of phonon-mediated and superconductor detector development, which already has broad impacts, in particular in the fields of Cosmic Microwave Background and of X-ray astrophysics. The proposed effort is likely to broaden this impact.