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Thread: On hadron colliders, dark matter and black holes

  1. #171
    Community Leader Facebook Connected torstan's Avatar
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    Oh dear, and here was me trying to keep this thread clean...


  2. #172

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    Pfft, it's still clean. If you don't need a translation to tell you why it's funny, than clearly you don't need to have it censored from you.

  3. #173
    Community Leader Facebook Connected torstan's Avatar
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    Okay, a small update. Unusually for this field there have been some dramatic developments. Firstly, there is news on the LHC.

    The bad news is that the LHC suffered an unfortunate incident in which a ton of liquid helium escaped after an electrical fault. In the technical report it mentioned some damage to 25 magnets (that's a lot, each full magnet using it the length of an articulated lorry) but CERN has assured everyone it has enough spare parts to repair them all. The safety systems worked, but the damage will take at least until the spring to repair. The LHC was scheduled to be off over winter anyway so this isn't too much of an issue. Unfortunately it means that the scheduled work for the winter - getting the LHC ready for its first full energy run - will have fewer people working on it. That means the LHC probably won't start at full energy, bt will instead (hopefully) make it to full energy some time in the summer of next year. So its a set back but not a catastrophic one.

    At the same time there have been new developments in space! A satellite experiment called PAMELA has reported that it has found a lot more antimatter than we ever expected to be up there. They've also found that the anti-matter has a distinctive energy. One theory (and the leading one at the moment) is that dark matter is annihilating in the galaxy and producing electrons and their anti-particle positrons with lots of energy. Those then fly through the galaxy and some of them hit the satellite. If this is true then we have just seen the first experimental signal of dark matter annihilations and we have a lower limit on the dark matter mass. That has, unfortunately, ruled out a couple of my predictions, but has opened up some interesting possibilities. So its interesting times for dark matter.

    Obviously happy to answer questions if anyone wants to know more.

  4. #174
    Community Leader RPMiller's Avatar
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    So I assume that means that the LHC still hasn't destroyed the world?

    Are there any suspicions of sabotage? We have seen a lot of crack pots and their worries, I'm wondering if they could have done something by working on the inside.

    Can you explain more about the "dark matter annihilating"? I'm not sure if that is a typo or I'm just not following it. Does that mean that dark matter is "less strong" and more likely to be destroyed rather than destroy something else?
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  5. #175
    Community Leader Facebook Connected torstan's Avatar
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    Its not sabotage thankfully. There was a pressure control valve that was faulty. It slowly opened when it should have remained shut and let liquid helium out. They found another couple that had the same fault so its manufacturing rather than sabotage. They'll replace them over the winter as well as cleaning up the damage from the problem.

    The dark matter can annihilate with itself. In particle physics we see that a particle and an anti-particle can annihilate. So if an electron and a positron (its antiparticle) hit each other then they annihilate to energy. Now we believe that whatever particle dark matter is made of has the bizarre property of being its own antiparticle. This means that if two particles of dark matter hit each other then they can annihilate to energy. This energy then produces two particles - in this case an electron and a positron.

    Now when two particles annihilate, their mass turns into energy. The amount of energy is given by E=mc^2. Now c^2 is a large number so you get a lot of energy for your mass. When that energy is turned back into matter - ie when the electron and positron are produced - you use some of that energy to create the mass - again through E=mc^2 - and the rest is kinetic energy. So by measuring the kinetic energy of the produced particle, you can find out information on the mass of the particles that annihilated to produce them.

    Now the issue here is that they've found positrons with energy that would require the annihilation of a particle with at least a hundred thousand times more mass than an electron, and about a hundred times the mass of a proton, and this gives us our first hint about the mass of dark matter. It means that the dark matter must be at least has heavy as an iron atom for example. Now an iron atom is a large object made of all sorts of substructure whereas we currently believe that the dark matter particles are fundamental objects - so that's pretty heavy.

    The fact that dark matter can annihilate is nothing too remarkable. If it hits normal matter it won't disappear - it has to hit another dark matter particle. In the same way, if an electron hits a proton it won't disappear, it has to hit a positron.

  6. #176
    Community Leader RPMiller's Avatar
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    Science is cool...
    Bill Stickers is innocent! It isn't Bill's fault that he was hanging out in the wrong place.

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    Community Leader jfrazierjr's Avatar
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    Does it scare the hell out of anyone else that they went "opps, mechnical failure caused something we did not anticipate in a project dealing with hugh amounts of energy in an attempt to create/detect theoretical particles that we really don't understand".

    You know it's a bad sign when the scientist says uh-oh, and and then runs from the room.
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    Doesn't bother me at all, it just gives me something new to map
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  10. #180
    Community Leader RPMiller's Avatar
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    Quote Originally Posted by Ascension View Post
    Doesn't bother me at all, it just gives me something new to map
    Would that be post-apocalyptic Europe?
    Bill Stickers is innocent! It isn't Bill's fault that he was hanging out in the wrong place.

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