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Experimental verification of QFT?

  1. Mar 22, 2008 #1
    What are the important experimental verifications of QFT that someone studying QFT should be familiar with?

    The wikipedia QED article mentions the anomalous magnetic moment of the electron and the Lamb shift.

    The Higgs Mechanism article states "Although the evidence for the Higgs mechanism is overwhelming, accelerators have yet to produce a Higgs boson". The evidence is overwhelming? Ok, what is that evidence? From what I can tell by the description in the article, it just seems that, given our understanding of how QFT's work, the existence of short range forces with massive quanta requires there to be a Higgs mechanism within the theory. So the "evidence" might simply be that it is logically necessary within the theory, e.g., there exist massive force carriers --> there must be a Higgs mechanism.

    Anyway, the Higgs question is somewhat secondary. If you know of experiments that strongly support it, please include them here.

    Even better, if you can give the name of scientists who performed the experiment, that would be great. And if you know of any textbooks which summarize such experiments, that would be supercalifragilisticexpialidocious.
  2. jcsd
  3. Mar 22, 2008 #2
    Two more come to mind, spontaneous emission of atoms in excited states is a prediction of QED not of ordinary QM, and the Casmir effect has been experimentally verified several times.
  4. Mar 23, 2008 #3
    Casimir effect, yes. Good one. Emission though I would say is the sort of thing which any QED candidate would have to incorporate. It is the very thing which the theory was developed to explain, so of course it has to do that much.
  5. Mar 23, 2008 #4


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    The reason we say that the usual Standard Model of Particle Physics with a single, real scalar field (a.k.a. "Higgs boson") is very well-supported by the evidence comes from precision measurements. People have calculated (to at least one loop, sometimes two) the contributions such a particle would make to various physical quantities such as the left-right asymmetries of electroweak gauge boson decays, g-2 of the electron/muon, etc. This list is quite extensive. The measurements that have been made to date agree remarkably well with the predictions that follow from a Higgs boson being there with a mass right around 114 GeV. Of course, this evidence must be taken with a grain of salt, and it typically is in the particle physics community, since just because it's "consistent" doesn't mean it must be that way. But that is what people mean.

    There are many (very large) experiments that have carried out these measurements. The most famous is the LEP-I experiment at CERN in the 1980's and early 90's. The many experiments at Fermilab and SLAC have also contributed significantly, as well as smaller experiments at BNL, JLab, DESY, KEK, etc. For a great summary of all of this, you can look up "Electroweak Precision" on the Particle Data Group's website (www-pdg.lbl.gov)
  6. Mar 23, 2008 #5
    Well, I was just saying that spontaneous emission is a feature of QFT (QED) that is experimentally known to happen of course, and is a feature exclusive to QFT and not ordinary QM.
  7. Mar 23, 2008 #6
    I know. And thanks for replying.
  8. Mar 23, 2008 #7
    Thanks, Blechman.
  9. Mar 24, 2008 #8
    As a historical note, the first drive towards QED was made by Bethe as an explanation of the Lamb shift.
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