Tuesday, December 13, 2011

Dorigo: Firm Evidence Of A Higgs Boson At Last!

This post is designed partly to send to to Dorigo's blog for more information as I am quoting his post and because, unlike the "mainstream" media, he actually is a professional particle experimental physicist and so gives the story a little closer to the truth then you will find other places.

That said, it looks like the search for the Higgs Boson, undoubtedly one of the most promenant searches in physics of our generation, may be nearing an end.  Just some quotes:
 I believe this is firm evidence of the existence of a SM Higgs at 124-126 GeV. 
First of all, we expected it to be around there...
Second, three-point-six standard deviations above background expectations from one experiment would not be enough ... But the two experiments are providing a very coherent picture. 
Third, the evidence is coming from different search channels, and they all appear to be coherent with the Standard Model expected cross section. 
Fourth, I do not believe we need to worry anymore too much about the look-elsewhere effect.
As you know, I have always said "half of three-sigma results are false" since there is just so often an unknown systematic skewing your statistics.  However, in this case two different experiments using  different channels arrived at the same answer.  One at 3.6 sigma and the other at 2.4 sigma.   Now I would say the risk of something being off by an unknown systematic is pretty minimal and thus I think we have reason to believe there is a high probability we are finally uncovering the Higgs: A boson at 124-126 GeV.  (Though it isn't official yet I should remind you!)

But still: Congratulations particle physicists!


  1. Awesome! I wish I understood the full implications of what this would mean. Anyone care to enlighten me?

  2. There has been a mathematical model, called the standard model, that has been around for the last several decades that has explained with near perfection all physics we know that isn't gravitational.  (Recently some things like dark matter and dark energy are not explained well by the model and are thus considered some of the biggest mysteries in physics.)

    But other then a few recent issues, the standard model seems to explain * everything* with no experiments that do anything but confirm it's predictions.... Except one!  The standard model has always assumed there exists a Boson named the "Higgs" that is responsible for some symmetry breaking that leads to particles having mass.   The standard model, with all of it's perfection, predicts that unless the Higgs Boson exists, particles wouldn't have mass!

    And though this Higgs Boson has been predicted by the standard model for decades now, experiment after experiment has failed to find it.  (This was largely expected since for various reasons this is a very hard particle to detect... but still there were people who were, and still are, a little worried.)

    So if the Higgs Boson is real, the last of the great predictions of the standard model will have been verified and thus there will exist a complete mathematical theory that explains *all* known physics except for gravity and a few other things like dark energy and dark matter.  

    So once the Higgs is found definitively, it will be a big deal.  Probably there will be Nobel Prizes for sure.  But the discovery of the Higgs will to physicists will go down as one of the great discoveries of our generation.   

  3. I see. That's sort of the view of it I had, so I'm glad to hear it confirmed.

    A few questions:
    1. Gravity is accounted for in General Relativity, by spacetime curvature, right? So the reason gravity is so hard is because we don't know why spacetime curvature causes gravity, or because we don't know why there is spacetime curvature?
    2. If the Higgs Boson is discovered (and it appears it is), does that lend credence to the idea of gravitons as being part of the SM and hence also explained by it? Or is that a really stupid question?
    3. Why are people so fascinated with magic, and mysticism when there is so much freaky crap in physics that I suspect most people have no clue even exists?

  4. 1.  Because the standard model assumes all forces are mediated by particles and if that is true general relativity is only correct in the same way Newtonian Gravity is:  matches large scale experiments but isn't what is fundamentally happening.  Ie. you feel gravity not because spacetime is actually bending but because a graviton is mediating the gravitational force that on large scales behaves what you would expect if space and time were bending.

    This led the Nobel Prize winning physicist, Weinberg, to conclude in his textbook on General Relativity: "I believe that the geometrical approach has driven a wedge between general relativity and the theory of elementary particles. As long as
    it could be hoped, as Einstein did hope, that matter would eventually be understood in geometrical terms, it made sense to give Riemannian geometry a primary role in describing the theory of gravitation. But now the passage of time has taught us not to expect that the strong, weak and electromagnetic interactions can be understood in geometrical terms, and too great and emphasis on geometry can only obscure the deep connections between gravitation and the rest of physics." 

    2. So sort of as I hinted at in #1.  The standard model being correct is another win for people who think all of physics is the result of particle interactions.  If so the day will come when we hopefully detect the existence of the graviton and General Relativity will become the next "Newtonian-like" theory that works on large scales even though it isn't fundamentally what is going on.

    3.  That is hard to answer.  

  5. To add to Joe's point, using a geometrical description similar to using general relativity for gravity fails for the other fundamental forces while quantum descriptions have been wildly successful for every force except gravity.  General relativity, on the other hand, has really only two big triumphs - cosmology and black holes - and neither of those are terribly practical, so quantum theories are far more popular than geometrical ones.  Einstein and many others worked really hard on geometrical theories of electro-magnetism without much success in the 50's and 60's, and since then most of the efforts to unify gravity and the other fundamental forces have tried to make gravity a quantum theory rather than making E&M and the nuclear forces geometrical.  String theory is the most prominent of these efforts.

  6. "a few other things like dark energy and dark matter"

    Just a point to those celebrating the Standard Model (and well they should, as this was a blasted hard experiment to set up and run): Roughly 96% of the Universe are in these two 'few other things' so there's still tons of questions and thinking and hunting to do.  The Standard Model can't be the final word.  

  7. General relativity, on the other hand, has really only two big triumphs - cosmology and black holes - and neither of those are terribly practical, so quantum theories are far more popular than geometrical ones.

    I don't think "practical" applies. The fact is that cosmology deals with a whole heck of what we know.  So those are some huge triumphs.

    All this ultimately just points to the problem or reconciling gravity and quantum mechanics in a robust way. I think people are becoming discouraged with string theory being the solution (despite some of the recent hype).  If we need to come up with a whole other theory I think we should be cautious assuming it'll be either a geometric solution or a particle based solution.

    Say what will about GR but it offers an elegant and simple way of thinking about the problem.  As such it's much like classical Newtonian mechanics, Maxwell's Laws, and arguably even basic QM with the wave equation.  As such I'd argue it's more likely that we'll see a revision of GR than merely throwing it out entirely or treating it instrumentally.  But of course no one knows. I'd note that in many ways the standard model is an approach that really hearkens back more to Newton than anything in that one thinks in terms of interacting particles. Sure the math is much more complex but it's that basic way of thinking with the strong empirical bent. (i.e. throwing a lot of values in from measurement rather than from basic principles)

  8. Honestly I was getting more excited by the thought they might not find the Higgs.  When I heard a while ago that there were some preliminary reasons to think it was pretty close to where it was predicted I was actually fairly disappointed. 

    I think physics would have been pushed to more progress had it turned out the Standard Model was fundamentally wrong. 

  9. BREAKING NEWS: (AP) A news conference was held today at the Malibu mansion of billionaire and technocrat Tony Stark where he announced that he has duplicated the work done at CERN and verified the existence of the Higgs Boson using the collider he built in his living room. 

  10. Clark,

      I was also hoping they didn't find the Higgs either so that we could have some new theory to work on.  That said, if the LHC found nothing at all there would be no more money to work on anything.

    So it is good they may have finally found something!

  11. Higgs is not here as yet because the fat lady has not sung!  Usually, one would not report "may bes" as proof. 

    JS, just a perspective: two different experiments (and instrumentations) can have two different sources of systemic errors.

    I am a bit concerned about CERN's way of science: first they have faster than speed of light neutrinos, and "may be" Higgs which some how fails to be unequivocal.  In normal parlance, this is called interim results and first look analysis, promising possibly, but no cigar.

  12. By practical I meant that quantum theories have had a huge impact on society in the form of computers, microwaves, lasers, etc. while the only application of GR is a slight correction to GPS signals.

  13. You are right - this is a preliminary result - but the fact that both detectors are seeing the same thing at the same energy is a pretty good indication that it's not a systematic error.  The odds of both detectors having such an error are vanishingly small, but it won't really be time to start handing out Nobel Prizes until both detectors have a 5-sigma result.

  14. Ususally, detectors are not at issue but the knowledge of underlying phenomenologies and expectations that introduce consistent bias in two or many instrumentatios.  If I understand the findings correctly, it is statistical comparision from measurements by two detectors, not an event seen by bothedetector.


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