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Science

Signs of Dark Matter From Minnesota Mine 158

Posted by Soulskill from the revenge-of-the-wimps dept.
thomst writes "Juan Collar, team leader of COGENT, an experimental effort to detect WIMPs (Weakly Interacting Massive Particles), recently presented a paper detailing 15 months of data collected via a pure germanium detector located deep in a Minnesota mine which seems to confirm similar results reported by a European effort called DAMA/LIBRA. The results are particularly intriguing, because they appear to show a seasonal variation in the density of WIMPs that accords with models which predict Earth should encounter more WIMPs in Summer (when its path around the Sun moves in the same direction as the Milky Way revolves) than in Winter (when it goes the opposite direction). The most interesting thing about the COGENT experiment is that the mass of the WIMP candidates it records is significantly less than most particle physicists had predicted, according to popular models. (Ron Cowen wrote an earlier article about COGENT last year that goes into a lot more detail about how COGENT works, what its team expects it to find, and why.)"
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Signs of Dark Matter From Minnesota Mine More

Signs of Dark Matter From Minnesota Mine

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  • winter? summer? (Score:3, Insightful)

    by conspirator57 ( 1123519 ) on Friday May 06, 2011 @10:21AM (#36047300)

    some of us live in the southern hemisphere, you insensitive clods!

    • And the experiment should be duplicated there.

      • Re: (Score:1)

        by Anonymous Coward

        It is being duplicated there: DM-Ice [fnal.gov]

        • Good link, but its just a proposal and a test at the ice cube cosmic ray experiment so far. But yes it should be duplicated there. That will take some time though, DAMA took 13 years to get a decent signal (8 sigma I believe). So by 2020, we'll have a confirmation, maybe. And even then we'll still not really know what dark matter is.

          ---

          Dark Matter [feeddistiller.com] Feed @ Feed Distiller [feeddistiller.com]

    • i would be angry at the sleight as well, except for the fact that, as an antipodean, you would instead feel pleasure at being overlooked

      and my apologies for not writing this upside down and backwards and inside out in meaning, as is antipodean custom

    • Re: (Score:3)

      by rossdee ( 243626 )

      For those of you that live in the southern hemisphere and don't have such seasons, winter is when it is cold. In Minnesota it can cool down to below 240K

      (Yes I am aware that Antarctica has winter, but nobody lives there apart from penguins)

    • Re: (Score:1)

      by Anonymous Coward

      some of us live in the southern hemisphere, you insensitive clods!

      Yes, but statistically speaking, not very many of us do, and since Slashdot is a USA-based site, and even the summary mentions that the researchers were in the Northern hemisphere (Minnesota and Europe) it's pretty easy to figure out what they mean, even for someone who lives in a topsy-turvy land where up is down and presumably left is right and you have to wear magnetic boots to avoid falling off the Earth.

    • Still have summer and winter don'tcha?

    • And what seasons do you have there.

      Most of the populated area just has summer year around.
      Or if you are at the south pole you have a full year of winter.

      For the rest of us who live in the correct Hemisphere (North) we have areas with seasons. Where when we say winter we mean it. and not just a cool summer day.

  • Science is good (Score:4, Insightful)

    by Tsingi ( 870990 ) <[graham.rick] [at] [gmail.com]> on Friday May 06, 2011 @10:26AM (#36047362)
    Nice to see that we are still supporting science for the sake of science, not just science that turns into profits for some private corporation.
    • Yeah, the stuff, despite these results, is still hypothetical but there's probably already sufficiently vague patents on it's commercial use. They'll proably get a cease and desist letter from a lawyer now. It's the way the world works.

    • Re: (Score:2)

      by khallow ( 566160 )
      Unfortunately, information about the existence of dark matter is useful knowledge in improving our understanding of the universe and focusing the efforts of thousands of physicists and their support personnel. So it's not science for the sake of science.

      • Re: (Score:1)

        by Anonymous Coward

        Why do you use the word "unfortunately" and what is your point in response to Tsingi? You make a valid statement, but your post comes off as argumentative to the one you are replying to. I don't see what point you are trying to argue.

        I think maybe you're just a dumbfuck. Or you're just disagreeing for the sake of disagreeing with his choice of words.

        • Re: (Score:1)

          by khallow ( 566160 )

          Why do you use the word "unfortunately" and what is your point in response to Tsingi? You make a valid statement, but your post comes off as argumentative to the one you are replying to. I don't see what point you are trying to argue.

          Let's look at two phrases from Tsingi's post:

          science for the sake of science

          and

          profits for some private corporation

          Why should I consider the former as somehow being "nicer" than the latter? As I see it, "science for the sake of science" is merely being unaccountable with Other Peoples' Money (OPM). There's no interest in the usefulness of the science. It's a comfortable myth for OPM-fueled researchers to embrace.

          At least with science for the sake of profits for some private corporation, you are doing something useful (and usually doing it with your own money not OPM).

      • knowledge in improving our understanding of the universe ... So it's not science for the sake of science.

        Ummm, methinks you should look up the definition of science

        • Re: (Score:2)

          by khallow ( 566160 )

          Ummm, methinks you should look up the definition of science

          And why would that help? I already know the common definitions of science. But to indulge your wishes, I went ahead and looked. Didn't see any insights there. Science isn't understanding of the universe, it's an activity which can improve understanding of the universe or it can generate "knowledge" for which there is no and never will be practical application.

        • I challenge you to give a definition of science that isn't immediately disputed by about 15 people. I'm pretty sure I can't.

          I'm not trying to be sarcastic or argumentative, I'm sincere. It is really hard to define but most people act as if it is obvious what it is.

    • This is especially interesting to me because another experiment failed to detect any evidence of dark matter [nature.com], which seemed to contradict the (not quite statistically significant) hints that CDMS may have detected dark matter last year.

      I'm also confused about which experiment this is. It says it is in the Soudan mine in Minnesota, but it isn't mentioned on either [umn.edu] of the websites [umn.edu] for the mine. Is it part of MINOS or CDMS, or is it something separate?

      Regardless, I have been really excited about these detectors

      • Re: (Score:3)

        by habig ( 12787 )

        It is indeed at the Soudan Mine. Our website doesn't do a good job at explaining the smaller experiments which operate there, although we are working on fixing that.

    • I'm on to you! Real Americans(TM) on the radio warned me about your plot to confiscate all our Bibles and guns! Yer obviously onna them people whut believes Obama was barn in Amurka! [/silly]

  • Wait.... (Score:1)

    by Anonymous Coward

    Why are the nerds trying to detect the wimps?

  • Science keeps amazing me!

  • http://en.wikipedia.org/wiki/Milky_Way [wikipedia.org]

    "The Sun orbits around the center of the galaxy in a galactic year—once every 225-250 million Earth years."

    has there ever been any research into odd or bad events in our geological record that occur with 237 million year frequency?

    because right now, at this moment, we are plowing through space we haven't plowed through in 237 million years. what the hell are we hitting? everything from asteroids to comets to various kinds of background radiation to fundamental particles could potentially vary periodically, according to this 237 million year loop

    yes, i take solace that most stuff around us is orbiting right along with us

    but not all of it

    • Re: (Score:1)

      by Anonymous Coward
      Just google "what happened 250 Million years ago" from Science Daily Nov 28, 2006 - http://www.sciencedaily.com/releases/2006/11/061126121112.htm [sciencedaily.com] The earth experienced its biggest mass extinction about 250 million years ago, an event that wiped out an estimated 95% of marine species and 70% of land species. New research shows that this mass extinction did more than eliminate species: it fundamentally changed the basic ecology of the world's oceans.

    • Re:that always bothered me (Score:5, Informative)

      by Framboise ( 521772 ) on Friday May 06, 2011 @11:21AM (#36047972)

      Note that the solar system co-rotates with the Milky Way matter around it, so the 225-250 Myr period with respect to an inertial frame is not relevant for dramatic effects. The sometimes discussed effect linked with massive extinction is the periodic crossing of the Milky Way plane, which occurs about every 35 Myr. The last great extinction ocurred 65 Myr ago, so one should have seen at least one or two of these plane crossing.

      Another possibility is the solar system crossing spiral arms, with period of order of 150 Myr, but this is debated.

       

      • Note that the solar system co-rotates with the Milky Way matter around it, so the 225-250 Myr period with respect to an inertial frame is not relevant for dramatic effects.

        Not so. The movement of stars is not similar. The rotation of the Milky way is far from homogeneous. It is thought that some stars are passing much faster than others -- kind of like a traffic model -- which creates the spiral arms, although that isn't fully understood too. There are stars bouncing up far from the plane, through the plane down and up again. There are all kind of weird distortions, also caused by Supernovae pressure, new stars, etc. It is like a boiling soup in 3D, the model of a stationary

    • The Permian-Triassic Extinction [wikipedia.org], "the Earth's most severe extinction event", occurred ~250Mya.

      However, you have to ask what danger could be fixed in space, relative to the Milky Way's position relative to the position of background galaxies. Everything is moving relative to everything else, why would a line between the centre of our galaxy and an arbitrary deep space object be a permanent danger?

    • Re: (Score:3)

      by kasperd ( 592156 )

      right now, at this moment, we are plowing through space we haven't plowed through in 237 million years. what the hell are we hitting?

      There couldn't possibly be anything static lurking around in that part of space, the gravity would pull it towards the centre of the galaxy. so, whatever was there would have to be moving around the galaxy at the same pace. It is of course not entirely impossible that there are objects in a non-circular orbit, but if there was we wouldn't be meeting it at the same spot every t

      • Well, there could be an object counterrotating. Same rotation period, opposite direction. Two encounters per period.
        However, I somehow doubt that it could maintain that counterrotation for too long.

    • http://en.wikipedia.org/wiki/Milky_Way [wikipedia.org]

      "The Sun orbits around the center of the galaxy in a galactic year—once every 225-250 million Earth years."

      has there ever been any research into odd or bad events in our geological record that occur with 237 million year frequency?

      because right now, at this moment, we are plowing through space we haven't plowed through in 237 million years. what the hell are we hitting? everything from asteroids to comets to various kinds of background radiation to fundamental particles could potentially vary periodically, according to this 237 million year loop

      yes, i take solace that most stuff around us is orbiting right along with us

      but not all of it

      It's not just the sun that orbits the center of the galaxy, but the entire solar system, including all of the rest of the solar systems. So assuming they are all rotating at the same rate in relationship to each other, then there isn't any new space to be plowing through.

      Put differently, whatever was in the space we currently occupy 237 million years ago has also moved away and is occupying different space. Now if your concern is some rogue comet or something that passes through this spot every 237 millio

      • my supposition is also absurd because the milky way itself is "moving" (orbitting?), in relation to other galaxies. there is no fixed point we are moving against

        however, it is a slightly intriguing possibility, no? that say, some fundamental constant we take for granted as constant actually might vary slightly across a 250 million year period... for some reason. wouldn't that be interesting? yes, this is wild conjecture, but you could certainly sit around and construct a few "what ifs" that would suggest su

        • Don't feel bad, it's occurred to me too.
          Improbable, yes, quite, but not absolutely totally impossible- after all, there is much to the universe still not understood.. like dark matter. (Personally I blame anti-dark matter ;-D )
          Seriously though, if there is something in the galaxy that caused the mass extinction, and it's location at any given time is randomized by the effects of gravity, it's not totally comforting to know we could still come across it at some point, and never even know when it's com

        • my supposition is also absurd because the milky way itself is "moving" (orbitting?), in relation to other galaxies. there is no fixed point we are moving against

          however, it is a slightly intriguing possibility, no? that say, some fundamental constant we take for granted as constant actually might vary slightly across a 250 million year period... for some reason. wouldn't that be interesting? yes, this is wild conjecture, but you could certainly sit around and construct a few "what ifs" that would suggest such a possibility. even though we aren't remotely able to ask serious science questions about such a hypothetical periodicity to... something, right now in our scientific maturity

          at least the thought is the basis for some perhaps compelling speculative science fiction, if not real science

          Definitely would work for science fiction, but the possibility is so remote as to be virtually 0. It is not just our solar system that is revolving in our galaxy which is revolving in our universe. All the other galaxies are also revolving, plus the distance between the galaxies is changing which would make the angles between the galaxies different today than they were 237 million years ago. Even the stars we see in the night sky are in different positions than they were 2000 years ago (and not just beca

      • Re: (Score:2)

        by Bengie ( 1121981 )

        Being that the Earth is on the outer edge of the galaxy, I could see the Milky Way plowing into some intergalactic radiation and us getting pushed to the front of it could cause issues. Or anything else like that.

        But more than likely, something that happened 237mil years ago was just a one time thing and just so happens to align with another number.

    • because right now, at this moment, we are plowing through space we haven't plowed through in 237 million years.

      More accurately, we're plowing through space we've never plowed through before, in the context of the universe. The Milky Way is *also* moving through space at about 2.1 million km/hr or 600 km/s [astrosociety.org]. I suppose it all depends on your reference frame.

    • If it's not orbiting it would just fall into the galactic center, so there would be no periodicity for hitting those particles.

  • Signs of Dark Matter From Minnesota Mine

    Coal?

  • The Soudan Mine can be toured (Score:5, Interesting)

    by swb ( 14022 ) on Friday May 06, 2011 @10:52AM (#36047662)

    The lab is located in a lower (the lowest?) level of the Soudan Mine. This mine is also a state park and you can tour the mine.

    The tour (when I took it, about 9 years ago) took you down to the same level as the lab, which I think is the lowest level of the mine or within a level or two of the lowest level.

    You ride a mine cart to a room where extraction of iron ore took place, hear some details about early mining, including a lights-out experience where they show you what it was like with nothing more than old-fashioned arc lamps on the miner's helmets.

    Before you leave this level, you get to go into the lab area and get a look around. I don't think you go much past the entry way, but it's neat anyway.

    The mine had a fire recently and I don't know if the tours are back in operation, but I believe they have every intention of continuing with them once they fix whatever happened.

    • Re:The Soudan Mine can be toured (Score:4, Interesting)

      by unimacs ( 597299 ) on Friday May 06, 2011 @11:18AM (#36047942)
      My family took the tour a couple of summers ago. Interesting history. They used to keep mules down there for months at a stretch. They were often in complete darkness. When brought back up to the surface they had to have their eyes covered until they were acclimated to light. The original miners used candles and the mining company made them pay for each one so they wouldn't be wasted (and to recoup some of the already paltry wages they were paying). If you are ever in that area it's definitely worth seeing, but frankly there's not too many reasons to visit that part of the state.

      • Charging for candles had nothing to do with wasting candles, it had to do with ensuring that the miners could never make enough to pay their debts. Same as it was for coal miners. Each pay check would dig them deeper in debt.

      • Re:The Soudan Mine can be toured (Score:5, Interesting)

        by Zenaku ( 821866 ) on Friday May 06, 2011 @12:09PM (#36048592)

        They charged the miners for candles, dynamite, and pretty much every other supply. See, (if I recall correctly from when I took the tour several years ago) the miners were not actually employees -- they were independent contractors. The company sold them supplies, let them into the mine, and then bought whatever ore they hauled out. This was mostly done to screw them. They could spend 18 hours a day hauling iron out of the mine for the company and yet not turn a profit.

        Also, incidentally, my group also took a full tour of the lab while we were down there -- I think they are happy to give tours, they just aren't regularly scheduled. We had called a few days before and one of the grad students working there met us and showed us around. Sadly, I was not struck by any super-power-granting science beams.

        • Yeah, that happens. My present job is helping make lightning detectors. When I applied for the job, I was heartbroken to learn there was not a cage somewhere in the building with a giant tesla coil set up for testing.

          I've had a number of disappointments like that. The dye laser I worked with in college looked like a fuel injector hooked to a paint bucket. The pump laser was an anemic old argon ion device that maybe put out 0.75 W on a good day. My senior project carbon 60 experiments used tiny glass am

    • Re: (Score:3)

      by habig ( 12787 )

      Work to fix the parts of the entry shaft which were damaged by the fire will stop public tours for the next few months, but we hope things will be back to normal at that point.

      Yes, "normal" includes regularly scheduled lab tours as well as historical mine tours. If you're up in this part of the world for touristy reasons (most of which involve fishing and canoeing) definitely look up the Soudan Underground Mine State Park.

  • Dark matter is more of a medium charcoal color.

  • When I first saw the title of the thread, my initial reaction was "How the hell is there dark matter in Minnesota? Did they find Nibbler's litter box or something?"

  • The problem with seasonal variation... (Score:5, Interesting)

    by Troggie87 ( 1579051 ) on Friday May 06, 2011 @11:20AM (#36047962)

    I did my physics undergrad at the University of Minnesota Duluth, and they graciously let me play around in the mine on occasion. I don't do much particle physics anymore so I'm not particularily equipped to judge their results, but I can say that all kinds of seasonal errors can be introduced in these experiments. Cosmic rays have a seasonal variation for example. Another that happens at Soudan for sure and possibly in Italy is seasonal variation in background radiation. The air circulation at Soudan is largely passive, and there is lots of radon gas seeping from the rocks. In the cold winter the exchange is excellent, but in the summer the circulation is terrible and you get anywhere from 5 to 10 times the radon background in the cave (air in the cave is warmer than outside in the winter and cooler in the summer, you can do the math).

    I'm not saying either of those are the cause of this, but there is good reason to squint hard at anything claiming "seasonal evidence" when the claim is extrordainary (in the sense that it is way off from any model). Scientists should be skeptical of this, especially since they are claiming a result before theory suggests a result should even be possible.

    • Radon experts are on site to deal with it. Even background Radon on the Earth's surface, .25 pCi/L is far, far too high to do dark matter experiments, nevermind 100 pCi/L underground. Radon has to be completely eliminated in these labs in the mines, and a 5-10 fold increase would be picked up by monitors.

  • I'm also glad to see that /. is working on the fortune generator. Too bad it blurts all fortunes in ROT-13. Hint for the curious:

    < uglymess.txt tr '[A-Za-z]' '[N-ZA-Mn-za-m]' | sed 's/%/\n\n/g' > clean.txt

    • Re: (Score:2, Troll)

      by arielCo ( 995647 )

      Corrected:

      < uglymess.txt tr '[A-Za-z]' '[N-ZA-Mn-za-m]' | sed 's/ % /\n\n/g' > clean.txt

  • Not so clear cut (Score:5, Interesting)

    by thegreatemu ( 1457577 ) on Friday May 06, 2011 @01:09PM (#36049304)

    There's a huge controversy right now in the field. The DAMA/Libra experiment has been claiming an 8-sigma excess for years which they say is consistent with dark matter, but they keep getting excluded by other experiments, most notably CDMS and Xenon. Every time their favored region is excluded, they come up with a new way to reanalyze their data to make it consistent again. But they have not ever released any of their data to the community (and hold patents on the type of crystal they use for their detector) so it's impossible to directly verify.

    CoGeNT first released hints of a low-energy excess which could be consistent with DAMA-type dark matter about a year ago. I was at the APS conference earlier this week where Collar released the seasonal modulation results which make it seem even more likely that they see the same thing as DAMA. However, just the next day, CDMS presented an analysis of their low energy data which is below their normal dark matter threshold (because the rate of background events in that region is quite high and poorly understood). They showed that, even if they didn't account for the known sources of background, the rate in their detector is inconsistent with CoGeNT's. As many people rightly point out, CoGeNT is seeing an exponential signal near threshold, which is what you'd expect to see in just about any detector with or without dark matter present.

    The whole situation is muddled even further by politics and personalities. Collar is respected as a scientist, but is also generally agreed to be an asshole. When he announced the annular modulation result, he spent 25 minutes of his talk attacking xenon on mostly pointless grounds, then had only a single slide showing the important result of the modulation. He finds tiny holes in other's analyses, but doesn't often present a very convincing picture of his own.

    tl;dr: The community is far from agreeing that what he and DAMA have seen are in fact WIMPs. CDMS and Xenon tend to have better established analysis programs and pay more attention to their systematics, and they still rule out both DAMA and CoGeNT. However, I think everyone at this point agrees they are seeing something interesting, just likely not WIMPs.

    • If not WIMPs, then what? Are there any other candidates, or did you mean entirely new particle that hasn't been thought of?

  • Is excreted by three eyed alien monkeys and is used to power space ships.

  • Of course the matter is dark, it's at the bottom of a mine shaft!

  • On April 27, I posted this comment [slashdot.org] on another story about an entirely different topic. Eventually, it got modded to +3 Insightful. Then, this morning, I discovered it had been modded all the way down to -1 Overrated.

    There's only one reason why a single moderator would spend that many mod points on down-modding a single post: to put it below the browsing threshold of virtually all /. readers. The question is, "Why?" And I suspect the only credible answer to that question is, "Because he is so consumed by ded

    • Re: (Score:2)

      by osu-neko ( 2604 )

      There's only one reason why a single moderator would spend that many mod points on down-modding a single post

      No single moderator did, since no single moderator possibly could. It takes at minimum four moderators to move a post from +3 to -1.

      In the interest of fairness, I urge you to read my comment [slashdot.org]. Whether or not the down-mod is undone, it deserves at least that much consideration.

      I doubt it. Posting off-topic about it just makes you sound like a complete idiot. It's not worth the time to read. (And this coming from someone who thinks both communists and libertarians are obviously morons.)

      • Re: (Score:2)

        by thomst ( 1640045 )

        There's only one reason why a single moderator would spend that many mod points on down-modding a single post

        No single moderator did, since no single moderator possibly could. It takes at minimum four moderators to move a post from +3 to -1.

        Your naivete is charming.

        Single users with multiple accounts? On /.? Inconceivable!

  • COGENT (Score:3)

    by students ( 763488 ) on Friday May 06, 2011 @02:35PM (#36050414) Journal

    This experiment is outside my field of expertise, but I know several people who worked on this experiment and have met Juan Collar several times. It seems like an excellent experiment, but there is a funny side to their results:- Juan Collar has been talking for a long time about how he has been very close to showing the DAMA claim of dark matter detection is incorrect, and now he has confirmed it. I often got the feeling that the COGENT team didn't really believe dark matter existed.

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