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Signs of Dark Matter From Minnesota Mine
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.)"
some of us live in the southern hemisphere, you insensitive clods!
"If still these truths be held to be
Self evident."
-Edna St. Vincent Millay
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.
http://en.wikipedia.org/wiki/Milky_Way
"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
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
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)
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.
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.
australia is known for arnold schwarzenegger, amadeus mozart, sigmund freud, franz ferdinand, the house of hapsburg, and "the sound of music"
please get a geography education
intellectual property law is philosophically incoherent. it is your moral duty to ignore it or sabotage it
Well, if it is a coal mine, wouldn't you expect it to be full of dark matter? ;)
This is especially interesting to me because another experiment failed to detect any evidence of dark matter, 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 of the websites for the mine. Is it part of MINOS or CDMS, or is it something separate?
Regardless, I have been really excited about these detectors for the last couple years (even more so than the LHC), and it is great to start seeing data.
http://wattsupwiththat.com/2009/06/13/results-lab-experiment-regarding-co2-snow-in-antarctica-at-113%C2%B0f-80-5%C2%B0c-not-possible/
I googled a bit.
-- perl -e'print pack"H*","6e656d6f406d38792e6f7267"'
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.
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.
Simon's Rock College
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.)
"Convictions are more dangerous enemies of truth than lies."