In this new data set there are indeed 2 events seen with characteristics consistent with those expected from WIMPs. However, there is also a chance that both events could be due to background particles. Scientists have a strict set of criteria for determining whether a new discovery has been made, in essence that the ratio of signal to background events must be large enough that there is no reasonable doubt. Typically there must be less than one chance in a thousand of the signal being due to background. In this case, a signal of about 5 events would have met those criteria. We estimate that there is about a one in four chance to have seen two backgrounds events, so we can make no claim to have discovered WIMPs. Instead we say that the rate of WIMP interactions with nuclei must be less than a particular value that depends on the mass of the WIMP. The numerical values obtained for these interaction rates from this data set are more stringent than those obtained from previous data for most WIMP masses predicted by theories. Such upper limits are still quite valuable in eliminating a number of theories that might explain dark matter. (emphasis added)So, Bryan's prediction was correct! Now if only the scientists would tell us what "reasonable doubt" amounts to ...
Thursday, December 17, 2009
Dark Matter Rumors (cont.)
The results that prompted the rumors noted in an earlier post have now been unveiled. They involve the detection of Weakly Interacting Massive Particles (WIMPs) which are predicted by some theories of dark matter. The group has provided a helpful two-page summary, with the key paragraph: