Dark Rumors

Cosmic VarianceBy Sean CarrollDec 9, 2009 11:10 PM


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All the physics blogosphere is abuzz about rumors that the CDMS experiment might have collected evidence for the direct detection of dark matter, and is going to announce their results on December 18. The original source was Resonaances, where you can read the basic story; see also New Scientist. It's to the point where it's more suspicious if we don't mention it than if we do, so here you are. Not too much point in speculating -- we'll find out next week! There was some misplaced excitement about a Nature paper, but it is true that CDMS has scheduled simultaneous talks at CERN, Fermilab, SLAC, and elsewhere. Steinn did the citizen-journalist detective work and dug up the abstract for Priscilla Cushman's talk at CERN:

I will present new results from the recent blind analysis of 612-kg days (before cuts) of data using the CDMS germanium detectors at Soudan. CDMS uses ionization and athermal phonon signals to discriminate between candidate (nuclear recoil) and background (electron recoil) events in Ge crystals cooled to ~ 50 mK. Timing, yield and position information allows us to tune our expected background leakage into the signal region to 0.5 events. I will report on what we saw when we "opened the box", whether we have seen WIMPs or not, and implications for future dark matter direct experiments.

It would seem unlikely to me that CDMS would be able to announce a cut-and-dried discovery of dark matter; that would require collecting an awful lot of data. (But what do I know?) It's more plausible that they would see some kind of provocative signal, but without quite enough significance to be definitive. With many different competing experiments, several of which have been working for quite some time now, it seems like the kind of result that you would gradually sneak up on, rather than dramatically capture in one fell swoop. Or maybe they're just updating us on their best limits, and some rumor-mongering has spiraled a bit out of control. We'll see.

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