The CDMS experiment today reported the observation of two events, with an expected background of .8 events (I gather this is a 1.5 sigma result, but there is no arXiv preprint yet). Based on this, the Guardian reports that “Hunt may well be over for mysterious and invisible substance that accounts for three-quarters of mass of universe” and Science News has Experiment Detects Particles of Dark Matter, Maybe. Science News quotes Craig Hogan as saying the results are “potentially very exciting”, and the Guardian has “If they have a real signal, it’s a seriously big deal.” Unfortunately they don’t have a real signal, so it’s not a seriously big deal.
I just noticed that the New York Times is also covering this, but more soberly, describing the results as “faint hints”. They do quote Gordy Kane, who describes the mood at the KITP in Santa Barbara as “a high level of serious hysteria”, which he then embodies by claiming “It seems likely it is dark matter detection, but no proof.”
For those unfamiliar with the terminology experimentalists use to characterize signals of various statistical significance, here’s a summary:
5 sigma: discovery
3 sigma: observation
1.5 sigma: noise
Update: Scientific American gets it right here.
Update: The paper is here. It includes the information that “Reducing the revised expected surface-event background to 0.4 events would remove both candidates.” There really literally is no signal here.
Update: Ethan Siegel’s blog posting about this explains the appropriate scientific response to the news that two events were observed when .8 were expected:
Well, La-dee Frickin’ Dah!
Adrian Cho at Science has an excellent piece about the story: Wimpy Evidence for Dark Matter Particles. He quotes two experimentalists who explain the significance of this (Richard Gaitskell: “Nobody should be attempting to say that this is evidence” for dark matter, and Edward Thorndike: “Absolutely not” an observation of dark matter). There’s also this comment from theorist Joseph Lykken:
Even so, Joseph Lykken, a theorist at Fermilab, says he’s relieved that CDMS has finally seen something. WIMPs are predicted to exist by theories involving a principle called supersymmetry, which posits a heavy partner for every particle currently known. Had CDMS continued to see nothing, the results would have undermined those theories. So seeing something is better than seeing nothing, Lykken says.
Lykken seems to be ignoring the fact that the new CDMS results, two events and all, rule out yet more of the supersymmetry parameter space. For an explanation of this, written when the last CDMS results came out, already causing problems for supersymmetry, see Tommaso Dorigo’s posting SUSY more unlikely by the new CDMS II results.
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