Dark matter not (yet) detected

Having written about the speculation, I suppose I should finish the story.  In a few talks yesterday, the CDMS dark matter detection experiment announced its latest results.  I didn’t hear the talks (at least one was streamed on the web, but I was in bed by then.)

They saw two events in their detector which look like what you’d expect from dark matter particle interactions, but two isn’t enough to conclude anything.  The group has elaborate procedures for calculating how many background events (i.e., events that look like dark matter but aren’t) might be seen.  Two is more than the expected number, but not by all that much: they estimate there’s a 23% chance of getting two background events.  To say they’d seen dark matter, that probability would’ve needed to be a tiny number.

Of course, it’s possible that these were dark matter events.  If so, I guess it means that the experiment is right at the edge of having sufficient sensitivity to detect dark matter particles.  This’d be great, because then future experiments would presumably be able to provide a real detection.

The group said they were planning to post a paper on the arXiv, but it’s not up yet.  Maybe they meant they’d submit it yesterday, and it’d appear today, or maybe they just didn’t get everything finished when they said they would.  I imagine it’ll be up soon.  In the mean time, there’s a brief summary of the result on their web site.  For those who want a bit more detail and can’t wait for the paper, JoAnne Hewett from Cosmic Variance was liveblogging one of the talks.

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