Combined limits on WIMPs from the CDMS and EDELWEISS experiments

The CDMS and EDELWEISS collaborations have combined the results of their direct searches for dark matter using cryogenic germanium detectors. The total data set represents $614\text{ }\text{ }\mathrm{kg}\ifmmode\cdot\else\textperiodcentered\fi{}\mathrm{days}$ equivalent exposure. A straightforward method of combination was chosen for its simplicity before data were exchanged between experiments. The results are interpreted in terms of limits on spin-independent weakly interacting, massive particle (WIMP)-nucleon cross section. For a WIMP mass of $90\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$, where this analysis is most sensitive, a cross section of $3.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}44}\text{ }\text{ }{\mathrm{cm}}^{2}$ is excluded at 90% C.L. At higher WIMP masses, the combination improves the individual limits, by a factor 1.6 above $700\text{ }\text{ }\mathrm{GeV}/{\mathrm{c}}^{2}$. Alternative methods of combining the data provide stronger constraints for some ranges of WIMP masses and weaker constraints for others.