The Cryogenic Dark Matter Search Experiment, results from the 2004 campaign and status of the current update

Abstract

The CDMS II experiment uses Z-dependent Ionization Phonon (ZIP) detectors made of Germanium and Silicon to identify nuclear recoils from Weakly Interacting Massive Particles (WIMPs) with near complete event-by-event rejection of various radioactive backgrounds. In 2004 CDMS II operated 6 Ge ZIPs and 6 Si ZIPs. The 74.5 live days of operation gave after cuts 34 kg*d exposure for the Ge ZIPs and 15 kg*d exposure for Si ZIPs. All criteria for identifying a signal from nuclear recoil due to WIMPs were developed blind with respect to the WIMP search data. The new 90% C.L. upper limit on the spin-independent WIMP-nucleon cross section is 1.6e-43 cm2 from Si, for a WIMP mass of 60 GeV/c2. The experiment has recently upgraded to 19 Ge ZIPs totaling 4.8 kg, and 11 Si ZIPs totaling 1.9 kg. The goal is to increase sensitivity with running in 2006 and 2007 by one order of magnitude.