Silicon detector results from the first five-tower run of CDMS II

We report results of a search for weakly interacting massive particles (WIMPs) with the Si detectors of the CDMS II experiment. This report describes a blind analysis of the first data taken with CDMS II's full complement of detectors in 2006--2007; results from this exposure using the Ge detectors have already been presented. We observed no candidate WIMP-scattering events in an exposure of 55.9 kg-days before analysis cuts, with an expected background of $\ensuremath{\sim}1.1$ events. The exposure of this analysis is equivalent to 10.3 kg-days over a recoil energy range of 7--100 keV for an ideal Si detector and a WIMP mass of $10\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$. These data set an upper limit of $1.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}41}\text{ }\text{ }{\mathrm{cm}}^{2}$ on the WIMP-nucleon spin-independent cross section of a $10\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$ WIMP. These data exclude parameter space for spin-independent WIMP-nucleon elastic scattering that is relevant to recent searches for low-mass WIMPs.