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Brookhaven Probing Unknown Form of Matter (Maybe)

Posted by michael on from the animal-vegetable-mineral dept.

boowax writes "The New York Times (free registration required) reports that there may be a new type of matter according to researchers at Brookhaven National Laboratory on Long Island. This apparently has come from interpretation of data gathered from work with muons and discrepancies between predicted wobble and the actual affect. Their are doubters though, who claim that the difference comes from problems with the calculations used for prediction and not a separate form of matter."

4 of 30 comments (clear)

  1. More informative article by mcelrath · · Score: 5, Informative
    Here is a far more informative article, straight from the horse's mouth. (I hate it when lay journalists "distill" the actual information down to nothingness and don't provide a reference to the original source...anyway) And Here is the experiment's home page, with a nice plot of the measurement.

    This is simply a fantastic experiment. The level of precision they have acheived is phenomenal, and they should all be commended for their efforts. The fact that the experiment was cancelled is a great tragedy. These kinds of experiments are a cheap way to look for new forms of matter. They won't tell you what the new matter is, but they will tell you it's there. They do this by very accurately measuring things that are easy to measure (like the muon's magnetic moment, or "g-2"), which are changed very slightly by the presence of new matter. The complimentary experiments are The Tevatron and The Large Hadron Collider which may be able to directly produce the new kinds of matter (if the new matter isn't too heavy) and thus identify it and study its properties.

    From a theoretical point of view, it is very easy to "screw up" this measurement. That is to say, if you write down a new theory that has almost any kind of new matter, it gives a contribution to the muon's g-2. This is why there was so much excitement last year when they announced a deviation from the Standard Model. One must remember however that the community's accepted standard for a "discovery" is 5 standard deviations between the measurement and the prediction. The top quark discovery had more than 5 standard deviations signal over background. I cannot find numbers on their home page but it appears from their plot that their measurement is around 2 standard deviations.

    Practically speaking, 2-standard deviation measurements pop up and then disappear all the time in physics. This is why we require the stringent "5-sigma" rule.

    -- Bob

    --
    1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.
    1. Re:More informative article by FredGray · · Score: 4, Informative
      This is simply a fantastic experiment.

      Thanks! (I'm a grad student on this experiment.)

      I cannot find numbers on their home page but it appears from their plot that their measurement is around 2 standard deviations.

      We compared the "world average" result against three recent published standard model evaluations by different authors. The discrepancies between our experimental result and these calculations range from 1.6 to 2.6 standard deviations.

      We should have a preprint available very soon now, by the way; we finished debating the last few words at a teleconference a few hours ago.

    2. Re:More informative article by FredGray · · Score: 3, Informative
      Definitely just politics--our measurement is clearly still limited by statistical rather than systematic errors. In the 2000 data that was just published, the statistical uncertainty was 0.7 ppm compared to about 0.4 ppm of systematics. That 0.4 ppm will almost certainly be reduced even further in the analysis of the 2001 data set, and presumably in any future data taking.

      Additional running time for our experiment was endorsed last year by the BNL program advisory committee. The budget cut was at the Presidential level, and it affects all DOE-funded high-energy physics at the Brookhaven AGS. This includes not just our experiment but also one of the high-profile rare kaon decay search experiments.

  2. Re:You'd fail class if you tried this by FredGray · · Score: 3, Informative
    So why did they release it? I mean, the work isn't finished, so what gives?

    What happened yesterday is that our collaboration announced our experimental result based on the data that we took in the winter of 2000. We have spent about two years staring at that data, and we are confident that we have extracted the right number from it. Consequently, we announced it yesterday and we are preparing a paper to submit to a journal.

    However, there is another side to the story. Other groups do theoretical calculations of what the standard model predicts we should measure in the absence of any "new physics." The confusion at the moment is on their side.