particles. Scientists have a strict set of criteria for determining whether a newdiscovery has been made, in essence that the ratio of signal to background events must be largeenough that there is no reasonable doubt. Typically there must be less than one chance in athousand of the signal being due to background. In this case, a signal of about 5 events wouldhave met those criteria. We estimate that there is about a one in four chance to have seen twobackgrounds events, so we can make no claim to have discovered WIMPs. Instead we say thatthe rate of WIMP interactions with nuclei must be less than a particular value that depends on themass of the WIMP. The numerical values obtained for these interaction rates from this data setare more stringent than those obtained from previous data for most WIMP masses predicted bytheories. Such upper limits are still quite valuable in eliminating a number of theories that mightexplain dark matter. What comes next? While the same set of detectors could be operated at Soudan for many moreyears to see if more WIMP events appear, this would not take advantage of new detectordevelopments and would try the patience of even the most stalwart experimenters (not tomention theorists). A better way to increase our sensitivity to WIMPs is to increase the number(or mass) of detectors that might see them, while still maintaining our ability to keepbackgrounds under control. This is precisely what CDMS experimenters (and many othercollaborations worldwide) are now in the process of doing. By summer of 2010, we hope to haveabout three times more Germanium nuclei sitting near absolute zero at Soudan, patiently waitingfor WIMPs to come along and provide the perfect billiard ball shots that will offer compellingevidence for the direct detection of dark matter in the laboratory.
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