back to article US sets up underground dark matter detector

US researchers* moved a step closer to establishing a new ‘dark matter’ detection experiment on July 13, moving several tons of kit into a former goldmine in South Dakota. The three-ton Large Underground Xenon (LUX) detector was installed into what was once the Homestake gold mine in the town of Lead, South Dakota. Due to go …

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  1. Anonymous Coward
    Facepalm

    self contradictory

    "The underground location protects the detector against both surface noise and solar radiation."

    Except solar neutrinos apparently.

    1. Trevor_Pott Gold badge

      Re: self contradictory

      Neutrinos aren't considered radiation. A neutrino smacking into something can cause Cherenkov radiation, but neutrinos themselves are not considered a form of radiation.

      Please go here: https://en.wikipedia.org/wiki/Radiation

      Catch up on the different types of particles (Photons, Neutrons, Electrons, relativistic Protons and relativistic Helium) that we consider to be radiation.

      These particles are radiation, and can all be considered ionising radiation under the right circumstances. Some can pass through quite a bit of material - especially the gasses that make up out atmosphere - and will cause Cherenkov radiation when they impact the detector.

      We need to bury detectors so far underground that that the chances of an accidental Cherenkov event are functionally eliminated. (As it is through Cherenkov radiation that we detect things like neutrinos.) WIMP interactions are no different than the standard rules for neutrino detectors. WIMPs basically don't interact with anything. Except on the *very* rare occasions that they do. When they do so, they ought to produce something very similar to Cherenkov radiation.

      Now, we have a good handle on the frequency of Cherenkov events due to neutrinos, and we can filter the background noise of such events due to radioactivity from things like the materials used to make the detector. But is we plopped the thing on the surface the potential sources of noise would be so high - overwhelmed by actual radiation - that we couldn't take useful measurements.

      In an ideal world, you'd filter out even neutrinos, but that is simply impossible. So the best we can do in the search for WIMPs is to build our detectors as far away from radiation as possible, and crank the sensitivity on the sensors up as high as our manufacturing processes will allow.

      Then the only things we have to filter are neutrinos and virtual particle collisions. Relatively simple…where simple is building a widget to detect particles that don’t interact with anything excepting through gravitational force.

      But no, the statement isn’t a contradiction…

      1. frank ly Silver badge
        Happy

        Re: self contradictory

        When I use a word, .....

      2. Destroy All Monsters Silver badge
        Devil

        Re: self contradictory

        Neutrinos are not dangerous .... yet! MUAHAHA!

        http://arxiv.org/abs/physics/9908017

        "High energy muon colliders, such as the TeV-scale conceptual designs now being considered, are found to produce enough high energy neutrinos to constitute a potentially serious off-site radiation hazard in the neighbourhood of the accelerator site. A general characterization of this radiation hazard is given, followed by an order-of-magnitude calculation for the off-site annual radiation dose and a discussion of accelerator design and site selection strategies to minimize the radiation hazard. "

        1. VinceH Silver badge

          Neutrinos are not dangerous

          Really? Have you ever run into a gang of them in a dark alley after they've had far too much to drink?

          1. TeeCee Gold badge
            Coat

            Re: Neutrinos are not dangerous

            It doesn't matter how much they've had to drink, it just goes straight through 'em you know.......

      3. Anonymous Coward
        Anonymous Coward

        Re: self contradictory

        I looked at your https://en.wikipedia.org/wiki/Radiation and only found 1 mention of neutrino and even that is about the anti-neutrino, nothing about whether or not it is radiation.

        Looked here - https://en.wikipedia.org/wiki/Neutrino and found that they 'emanate' from the sun, or they are 'emissions' .

        It looks like they'll do anything to avoid the word radiation, very suss imho.

        If they radiate from a source they're a radiation, see walk, quack, duck.

        1. John Brookes

          Re: self contradictory

          I can't see any particular reason for neutrino beams not being radiation, but the rest of his point still stands. I guess that if it is not considered radiation, it could only be because of its vanishingly small interaction cross-section....

          Sticking the experiment in a mine is required to (hopefully) keep the SNR manageable. On the surface, you would just have a really rubbish cosmic ray air shower detector.

        2. Annihilator
          WTF?

          Re: self contradictory

          "It looks like they'll do anything to avoid the word radiation, very suss imho."

          You think the world is that much out to get you that they've redefined what radiation means? That's a very special view of the universe you have...

      4. BristolBachelor Gold badge

        Re: self contradictory

        I'm a bit lost here. This detector would seem to operate using similar principles to the nuetrino detectors that already operate (Except possibly the ice cube). As such, it surely will react to neutrino events? If we wish to subtract the expected neutrino events based on measurements previously taken with neutrio detectors, how sure are we that those nuetrino events previously recorded were not in fact WIMPs as well?

        (I won't even get into the whole Dark matter is only needed to satisfy some models that assume "redshift" == "Dopler shift" and could not be caused by variances in the fine structure constant or photons losing energy in collisions with electrons in plasma clouds)

        1. Destroy All Monsters Silver badge
          Holmes

          Re: self contradictory

          > how sure are we that those neutrino events previously recorded were not in fact WIMPs as well?

          Good statistics and good calculation, I would think. Have a gander: http://arxiv.org/abs/1107.1295

          > I won't even get into

          This is good because...

          1) Dark matter is needed to explain Galaxy cluster clumping and Galactic rotations

          2) Doppler shift is written Doppler shift

          3) Cosmological redshift is not technically Doppler shift

          4) Variances in the fine structure constant would be clear as f*ck. Indeed, the possibility of very small variances caused a ruckus back in 2000 or so, but nothing conclusive was seen.

          5) Tired light theory was tired when the Hubble Telescope wasn't even up

          Any questions?

        2. Trevor_Pott Gold badge

          Re: self contradictory

          Cherenkov radiation is a photon. WIMPs barf up a photon AND an electron; which causes another Cherenkov event. Thus the pattern and frequency of the events can tell you one from the other.

          That, and a god-awful amount of maths.

          1. Mallorn
            Boffin

            Re: self contradictory

            " A neutrino smacking into something can cause Cherenkov radiation"

            Not quite. A neutrino with sufficient energy which hits something and interacts (the latter is very unlikely) can either convert into the same flavour of charged lepton (electron, muon or tau) or can kick an electron out of matter.

            It is this high energy charged particle which causes the Cherenkov radiation, not the neutrino itself because you have to have a charge to generate Cherenkov light. Also Cherenkov radiation is not one photon but a whole series emitted in a cone similar to the sonic boom of a supersonic plane but with light, not sound. The frequency of the radiation is determined by the refractive index of the material.

            1. Trevor_Pott Gold badge

              Re: self contradictory

              @Mallorn; you are correct. But I was trying to stay a little high level here. It is the difference between trying to explain that a matter/anti-matter reaction doesn't provide 2(MC^2) energy "beacuse half the mass is lost as neutrinos" and explaining that "half the mass is lost as neutrinos after first going through a series of intermediary decay states, all of which occur so rapidly that we cannot possibly capture and make any use of."

              To say "the neutrino causes Cherenkov radiation" may not be 100% correct (it omits steps,) but the result is the same: a neutrino impact causes Cherenkov radiation, which is what we measure. a WIMP impact should cause a different Cherenkov distribution (with aditional non-Cherenkov photon events.)

              So a WIMP detector and a neutrino detector are remarkably similar; so much so that the WIMP detector could never have been built without the technologies we created for neutrino detection. Indeed, data we pull from this detector will probably be mined by the teams not only for WIMP detection, but additional information on neutrinos.

              Either way; there's a balance between spelling out the total sequence in such events and "trying to simplify the science enough that people are likely to retain the important bits."

              The important bit about how this detector works is "when a Neutrino or WIMP hits something, we see a flash of light (photons.) Based on the pattern, frequency and intensity, we can tell if this was caused by a neutrino, a WIMP or background radiation. However, we can only do that if the damned thing is buried so far underground that background radiation is as close to null as possible."

              After all, the original comment was regarding "radiation," and why neutrinos aren't. (Thier lack of interaction.)

              That said, I do have to go plunder the ArXiv for information about this supposed TeV neutrino "radiation" concern. It hurts my science a little. Neutrinos don't have charge, and are already just-barely-subliminal in speed...exactly how does one impart more energy to a neutrino such that it is suddenly a radiative concern? Something doesn't parse there...

  2. whatthe
    Stop

    really?

    idk what they are doing messing around with dark matter but it is obviously anti-matter for a reason. i dont wanna detect it because best case scenario?? a matter and dark matter atom cancel each other out, where do they go? well obviously somewhere else... einsteinrosenbridge? lol singularity. take us all with them. they should just leave that stuff alone...

    1. Destroy All Monsters Silver badge
      Stop

      Re: really?

      Your medication, sir!

    2. John Brookes

      Re: really?

      This *is* satire, isn't it?

    3. Z-Eden
      FAIL

      Re: really?

      Tinfoil hat, sir?

  3. Destroy All Monsters Silver badge
    Holmes

    Also, Reg, if you have time

    I suppose this is "Stanford", not "Sanford"

    And using Xenon is a well-established practice:

    http://en.wikipedia.org/wiki/XENON_Dark_Matter_Search_Experiment

    1. Kirbini
      Thumb Down

      Re: Also, Reg, if you have time

      And you would be incorrect.

      You are correct in noticing that there is no such thing as Sanford University (el Reg, please note) but there is also no single University attached to the lab. The Independant lab is named after its primary backer T. Denny Sanford who donated $70 million to create it. The principle researcher is from Berkley and the second researcher in command is from the South Dakota School of Mines and Technology.

      As an aside, T. Denny made his money in the credit card business selling 79% interest rate credit cards to those in need (South Dakota is notorious for lax laws regarding credit). Just about everything in SD has had his name attached to it in the last decade as he likes to give his money away in startlingly large sums. $400 million to local medical/hospital group (which promptly renamed to Sanford Health and instantly became the big kid on the block in local clinics, hospitals and the like), $45 million for a health facility/arena, $50 million to build clinics in South America, $20 million to expand hospitals in Aberdeen, SD population 26,000 (approximately $10,000 per person within a 100 miles). You get the picture.

      1. SYNTAX__ERROR
        Holmes

        "there is no such thing as Sanford University"

        The people who made this web site at least, would disagree with you:

        http://www.lsu.edu-group.org/

      2. Anonymous Coward
        Anonymous Coward

        @ Kirbini

        There is no such word as "Independant". Spelling check functionality is available in popular browsers.

        ADJECTIVE Dependent - relying on something

        NOUN Dependant - a person who depends on something, e.g. your children

        1. illiad

          Re: @ Kirbini (AC 16th July 2012 15:38)

          ..but the IS such a thing as "grammer nazi"

          watch out for the trap.... :P :)

  4. Andrew Beresford
    Thumb Up

    In the UK too

    We're doing this kind of work in the UK too: http://www.hep.shef.ac.uk/research/dm/drift.php. Boulby Mine has been involved in this kind of work for quite some time.

    Disclaimer: I work for the University of Sheffield.

  5. amanfromMars 1 Silver badge

    Getting Down to the Nitty Gritty .....

    US sets up underground dark matter detector ...... Wow, whoever would have thought that bullshit travelled so far and so deep in the US.

  6. andy k O'Croydon
    Coat

    i keep reading...

    ...the LUX detector as the LUX capacitor.

    The one with the shiny glasses in the pocket.

    1. darkmage0707077
      Joke

      Re: i keep reading...

      88 particles per hour? Great Scott!

  7. Sceptic Tank
    Paris Hilton

    Forget the WIMPs

    Can a nice looking girl in a bathtub please demonstrate this LUX for us?

    On that note. This sounds like "alternative universe" stuff to me. I hope those scientists aren't going to peep into somebody's bathroom on the "other side". There could be consequences.

  8. Ugotta B. Kiddingme
    Joke

    collisions? wimps?!?

    I'd expect any wimp colliding with Xena to have the crap beaten out of it. Lucy Lawless probably doesn't take guff from anyone, let alone wimps...

    1. Anonymous Coward
      Anonymous Coward

      Re: collisions? wimps?!?

      I would rather collide with Renee O'Connor...

  9. asdf Silver badge
    FAIL

    not to be a dick

    But I guess this experiment will succeed in setting a baseline of knowing how not to find WIMPS. My prediction is they find nothing. It will be the gravity wave detector all over.

    1. Orv Silver badge

      Re: not to be a dick

      Of course, that's useful information in itself, just doesn't make for headlines that are as interesting.

  10. Mallorn
    Boffin

    Correction

    "That detector helped 2002 Nobel Laureate the late Dr Ray Davis detect “flavor (sic) changes” in solar neutrinos"

    Ray Davis did not detector flavour changes in solar neutrinos! He detected a shortfall in the number of electron neutrinos predicted by solar models but did not make any measurement which showed why there was such a shortfall. This lead to what was called the "solar neutrino problem" where multiple experiments confirmed that the electron neutrino flux was only ~33-50% of what was expected.

    If was the Sudbury Neutrino Observatory (SNO) [http://www.sno.phy.queensu.ca/] which showed that solar neutrinos changed flavour by measuring the total flux of all flavours vs. the flux of just the electron flavour.

    Not convinced? Check the Nobel prize citation for Davis: "for pioneering contributions to astrophysics, in particular for the detection of cosmic neutrinos" [http://www.nobelprize.org/nobel_prizes/physics/laureates/2002/] - no mention of flavour oscillations!

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