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Space Science

Dark Matter Hinted at Again at Cresst Experiment 80

Posted by samzenpus
from the look-what-we-found dept.
physburn writes "The BBC is reporting recent results from the Cresst dark matter search in Italy. Between 2009 and 2011, Cresst have seen 67 events, a 4 sigma detection of dark matter particles with a mass of either around 15 GeV or 25 GeV. The results are near those previous results from DAMA and Cogent. So has dark matter finally been found, and if so what is it?"
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Dark Matter Hinted at Again at Cresst Experiment

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  • Not yet. (Score:4, Informative)

    by Claws Of Doom (721684) on Wednesday September 07, 2011 @05:49PM (#37334010)
    4 sigma detection != (officially) found. You need 5 sigma for "discovery" status. The BBC have a good explanatory piece: http://www.bbc.co.uk/news/science-environment-14811580 [bbc.co.uk]
  • by AnonGCB (1398517) <7spams AT gmail DOT com> on Wednesday September 07, 2011 @05:51PM (#37334022)

    Dark matter always seemed like a convenient hand wave, but I'm thrilled if there's some concrete evidence of it. I do love being wrong!

    • by chill (34294) on Wednesday September 07, 2011 @05:59PM (#37334098) Journal

      I do love being wrong!

      You're married, aren't you? Sounds like for some time, too.

    • by Jello B. (950817)
      It's not a cop out. [wikipedia.org]

      The correspondence of the two gravitational lens techniques to other dark matter measurements has convinced almost all astrophysicists that dark matter actually exists as a major component of the universe's composition.

    • by lgw (121541)

      Dark matter was a convenient hand wave for the galaxy rotation problem, and just one of many hypotheses. But the the CMBR measurements also showed dark matter in the early universe, and in the same proportion predicted. That was as solid a confirmation as you ever get in cosmology.

      What's interesting now is what it's made of - all we know is there's no interaction with photons, and no frictional clumping as you'd see in normal matter (or at least not in the wide range of energies involved in galaxy formati

      • by Chris Burke (6130)

        What's interesting now is what it's made of - all we know is there's no interaction with photons, and no frictional clumping as you'd see in normal matter (or at least not in the wide range of energies involved in galaxy formation).

        Like neutrinos, only heavier. Perhaps the hypothetical neutralino. They only interact via the weak force and gravity, which would explain the apparent behavior. Or maybe something completely different, but then these detectors would probably not be able to find it at all, which would be a bummer.

        Man, it's so painful waiting for sufficient data to show up in real-time. These tantalizing but inconclusive hints are like torture! I can only imagine what it must be like for those actually doing the work --

      • by ynotds (318243)

        no interaction with photons, and no frictional clumping

        AFAIK this is one point not two as frictional clumping is mediated by photons, as at some point are all our observations. Not that I don't fully accept the evidence for dark matter, nor have any sympathy with DM deniers. From a history of science perspective, their kind have always been wrong.

        • by lgw (121541)

          AFAIK this is one point not two as frictional clumping is mediated by photons,

          Frictional clumping in normal matter is about photons. There could be 17 additional fundamental forces that only interact with dark matter for all we know - but none of them can produce friction (exept perhaps at very low energy levels).

      • What's interesting now is what it's made of - all we know is there's no interaction with photons, and no frictional clumping as you'd see in normal matter (or at least not in the wide range of energies involved in galaxy formation).

        It's 4 space dimension matter rather than 3 space dimension. Since 'our' 3 space dimension matter has nil (0.0) 4d space volume, there is basically zero % chance of interaction*. Likewise with other lower or higher dimensional matter.

        Additionally 4d photons don't interact directly with 3d matter, etc.etc.

        The interesting thing is that spacetime curvature still occurs... which explains the gravitational effects of different dimensional matter.

        * I can't recall

        • by mug funky (910186)

          i like to think of it as looking at a game of pool if you're sitting with your eye level aligned with the side of the table, and a whisky in your hand (that part is very important). the table is essentially reduced to 1 dimension instead of the 2 that are necessary to model it (excluding corner cases such as spin, and balls becoming airborne).

          when a shot is taken, balls appear to either collide and bounce, or pass through each other. far more pass through each other than collide, and it's nigh on impossib

        • by lgw (121541)

          That doesn't hold up. If dark matter had friction (regardless of why), the dark matter in galaxies would tend to form disks - it doesn't. Also, in a 4-spatial-diminsion universe, there are no stable orbits, and no large scale structures like galaxies could form if gravity fell off as R^3.

        • by Chris Burke (6130)

          Dark matter does not appear to interact with itself any more than it does with normal matter. That's why in galactic collisions the dark matter of one galaxy will pass right through not just the dust clouds of the other galaxy, but its dark matter as well.

    • by DrJimbo (594231)

      Dark matter always seemed like a convenient hand wave, [...]

      It might well seem that way, but I don't think it really is. In fact, it would be kind of strange if there was no dark matter because that would mean everything in the Universe glows. When you think about it a bit, you realize there's got to be a least some dark matter so the only question is: how much is there?

      ISTM the dark matter hypothesis is completely reasonable. If anything, it is more humble than arrogant because it's not assuming that the only things that exist are the things we can directly s

  • by Xerxes314 (585536) <clebsch_gordan@yahoo.com> on Wednesday September 07, 2011 @06:04PM (#37334132)
    It's consistent with DAMA and Cogent in the sense that it's ruled out by those experiments at only a few sigma. It's "near" Cogent in the sense that 8 is "near" 25, and it's "near" DAMA in the sense that 35 is "near" 10; that is, it's not near at all. It's ruled out by Xenon by many orders of magnitude. My favorite theoretical model to explain these results is IDM (Italian Dark Matter) [blogspot.com], which consists of dark matter that only exists in Italy. Presumably similar particles are responsible for whatever makes Guinness taste better in Ireland [wiley.com].
    • If I had mod points..... IDM will be my acronym of the week.
    • (paraphrasing here, this was almost 20 years ago)

      Friend: "Look at this! It's Guiness! Real. Live. Irish. Guiness! And I got it.... at the [insert early 90's supermarket chain here]."

      Me: "Oh I've heard of that stuff. Is it really all that special?"

      Friend: "What? Philistine! Look at this stuff. It's blacker than your soul. You could eat this for lunch. Many Irish do. It takes your girly American lager out back and beats it with a 2x4. Look, even the can has this automagical thingy inside it to reproduce the l

    • by JamesP (688957)

      So do you think Cogent should move to New Jersey??

    • Italian Dark Matter. Do you mean Espresso?
    • by Anonymous Coward

      From your own link, Cresst's 'M2' preferred mass region ranges from 9 to about 13 GeV, which is indeed 'near' both Cogent's 8 and Dama's 10.
      At first glance it may look like this is ruled out by Xenon, but there is a lot of debate about the validity of Xenon's results in this low mass region, and just a small shift would make Cresst's results perfectly consistent with Xenon's.
      Of course the Cresst signal could still disappear, but with three independent experiments claiming evidence in such a small region, th

  • by overshoot (39700) on Wednesday September 07, 2011 @06:23PM (#37334268)
    Starts with a Bang [scienceblogs.com] is an astrophysics professor's coverage of dark matter and what we know about it (including why we believe it makes up most of the matter in the universe.)
  • by bcrowell (177657) on Wednesday September 07, 2011 @06:54PM (#37334544) Homepage

    There are lots of experiments of this type running right now. This team, CRESST-II, has announced that they have more events than can be explained by their background. However, that's not really the most convincing evidence you could ask for, since the background could have been underestimated. A more convincing thing to see is that some of the experiments are reporting signals that are modulated by the expected amount on a yearly basis by the earth's motion relative to the frame of the cosmic microwave background. Here [arxiv.org] is a paper that includes a survey of the the results as of June. There are some apparent contradictions between some groups' positive results and others' negative results.

    • Most the the dark matter experiments are looking for WIMPs, not Axions, those, no my knowledge have been left behind by low energy detectors. I could very likely be wrong, I extrapolate far too much from documentaries, hehe. However, a yearly rotation will have no effect in comparison to the CMB, which comes from all directions at more or less the same direction; it's VERY uniform. So I highly doubt a 30km/s rotation around our sun will impact our interaction with the CMB when our relative motion to it a
      • by bcrowell (177657)

        So I highly doubt a 30km/s rotation around our sun will impact our interaction with the CMB when our relative motion to it around the center of the milky way seams to be 390 KM/s.

        You're right, it isn't the velocity relative to the CMB that's relevant, it's basically the velocity relative to the galactic halo. The dark matter particles they claim to be detecting would be gravitationally bound to the galaxy. I think the rest of what I wrote is correct. Check out the link I gave in the GP post, and also this paper http://arxiv.org/abs/1011.3076 [arxiv.org] , where they predicted the yearly modulation before they started the experiment. They measure a yearly modulation of about 16%, and that is app

  • I consistently see it every night after a drinking binge.

  • The abstract talks about "730 kg days". Huh?

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