Before The Higgs - Text For The Trash Bin
    By Tommaso Dorigo | October 9th 2013 02:53 PM | 11 comments | Print | E-mail | Track Comments
    About Tommaso

    I am an experimental particle physicist working with the CMS experiment at CERN. In my spare time I play chess, abuse the piano, and aim my dobson...

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    Today I was in the mood of cleaning up some areas of my labyrintic hard drive, after having performed a periodic backup of its contents. I thus came across some pieces of text that had been sitting in a remote folder, waiting to be used for a project now obsolete. I was about to just dump these files in the trash bin, when it occurred to me that this was stuff that had taken me some good time to put together, and maybe there was a better use for it.

    Indeed, I have a blog ! This blog is in some sense a kind of "trash bin" of my thoughts, which I happily share with whomever is willing to read them. Now, the text I decided to save from oblivion is not particularly good, and it is obsolete because it talks of an era now gone - the pre-Higgs-discovery time when we could still speculate on whether the Higgs was actually a "fairy field", as a friend of mine would call it. However, it does transport us back to the pre-discovery time and it describes in simple terms the situation, in a way that might be of benefit to some of you.

    So I am offering it below, with the caveat emptor clause that of course things have changed ! Not everything, however: the statements about the standard model being incomplete, and the mysteries surrounding the fermion masses, are still all the rage today...


    Despite the continuing failure to find a Higgs boson, which the theory cannot do without, the standard model has been overwhelmingly successful in the last thirty years. It is maybe ironical that the Higgs boson, despite being the cornerstone of the whole theoretical construction, is affecting so little the observed phenomenology of sub-nuclear processes; if its influence were stronger, physicists might at least obtain an indirect evidence of its existence, but Nature has chosen otherwise. Even with no knowledge of the Higgs boson mass –a quantity that the model itself cannot predict- the standard model provides the tools to compute extremely accurate predictions for the observable features of electroweak processes. The availability of collider data probing the properties of weak bosons has allowed a verification of those predictions, and the result has always been a near-perfect match.

    The best example of the new discipline flourished in the late eighties, called “precision tests of electroweak theory”, is the corpus of results obtained by the four experiments at the LEP synchrotron of the CERN laboratories in Geneva, and by the one at the Stanford Linear Accelerator Center in California. By colliding 45-GeV electron and positron beams in the core of the Aleph, Delphi, L3, and Opal detectors at CERN, and the SLD detector at SLAC, several million Z bosons were produced through the picture-perfect production process of electron-positron resonant annihilation. The created Z particles immediately decayed into fermion-antifermion pairs with different rates which depend on the details of the theory: the simplest precision test was thus just comparing the observed and predicted rates of the different kind of events.

    With millions of Z decays, the LEP and SLD experiments could examine in exquisite detail the predictions of the standard model concerning not just the relative rates of decays of the Z boson into different final states, but also the angular distributions of the produced particles, the asymmetries resulting from the intrinsic properties of the particles involved in the reactions, etcetera. Literally thousands of man-years of studies and analysis have gone in that effort, such that the Particle Properties data book, the bible of experimental particle physicists and a compendium of all the human knowledge of the properties of sub-nuclear particles, contains a hundred pages of summarized results, none of which exhibits a significant deviation from the model predictions. No anomalies there: the model is successful.

    Using the mass of data acquired at LEP and SLAC, plus the additional information coming from several other particle physics experiments throughout the world, it is indeed possible to try and discern the elusive influence of Higgs particles in the studied reactions. Everything seems to consistently point to the existence of that new neutral boson, whose mass should not be far from that of its electroweak W and Z cousins. Few particle physicists doubt that a Higgs boson with a mass in the 100-200 GeV range will be discovered in the next year or two by the new experiments at the Large Hadron Collider at CERN. Otherwise, the surprise will be even bigger.

    And physicists would love to be surprised. Anything new and unexpected can be used as a tool with which to make way into new unexplored territory. In the case of the standard model, however, there is an additional bonus from anything not contained there: physicists know that regardless of its beauty and the precision of its predictions, the standard model is incomplete, and to some extent unsatisfactory. For sure, it cannot be the final word on the theory of matter and interactions. The model does not include gravity, it does not provide a straightforward means to unify the four forces together, and it presents at least one or two nagging technical issues. But these issues are complex, and they are out of scope here.

    Instead, even without looking at the big problems mentioned above, which are given no solution within the existing framework, for an experimentalist or for a bystander the most nagging issue making the standard model not totally satisfactory is probably of more down-to-earth nature. This is the observation that the theory contains over twenty parameters whose value is only known through experiment: there are no ways to calculate them from first principles. The presence of twenty-something numbers that have a unexplained value is annoying in a theory so beautiful and successful.

    Among the unexplained parameters of the standard model the ones we would love the most to explain are the fermion masses. It would be so nice if we could know just why the muon is two-hundred times heavier than the electron! We do not know why that is so. This leaves us to wonder what it is that is really being hidden from our view. To Rabi’s question “Who ordered the muon?”, we are compelled to add “and why the heck is it so heavy?”. Similar questions of course surround each of the fermions. Note that the Higgs boson, with its coupling to fermions proportional to the fermion mass, does not “explain” in any way the different values that these masses have. The explanation is deeper, if one exists; but we have not found it yet.

    We are thus led to believe that the standard model needs to be replaced by a deeper, more fundamental theory. And we can only hope that this new theory will give answers to all our questions, rather than answering just a few while adding new, more impenetrable ones.


    John Duffield
    LOL! I had a laugh at your intro, Tommaso.

    But this isn't trash. This is good stuff. This is the sort of stuff people should be thinking about. IMHO it's been badly overshadowed by the Higgs publicity and stuff like SUSY.
    Thanks John!
    Had you heard of feasibility of Bohr orbit quantization for multi-electron.
    I am Chinese ,would you help me ?

    No, if you are Chinese then no, no way.

    ... :) Sorry I could not resist - but it was highly called for: what does being
    Chinese have to do with it ?

    Anyway, the real answer is no, I have no news about that. Sorry...

    As to how to "… "explain" … the values that … the fermion … masses have …",
    consider the work of Armand Wyler in C. R. Acad. Sc. Paris 272 (1971) 186-188
    in which he calculated the fine structure constant and the proton/electron mass ratio
    based the geometry of complex domains related to group symmetry.
    Wyler's work was dismisssed in the 1970s by the physics establishment as mathematical numerological coincidence with no physical interpretation, so there was for many years no serious attempt to further develop and expand his approach,
    in 2005 Carlos Castro wrote "On the Coupling Constants, Geometric Probability and Shilov Boundaries" posted in 2007 at
    which describes physical interpretation, such as
    "… the correspondence between the Feynman fermion (electron) propagator in MInkowski spacetime
    and the Bergman kernel of the complex homogeneous domain after performing the Wyler map between an unbounded domain (the interior of the future lightcone of spacetime) to a bounded one …".
    Carlos Castro also discusses how the Wyler approach can be used for calculations relevant to weak force and color force strengths.

    Physicists who are now, in light of LHC results, looking for "… a deeper, more fundamental theory …[that]… will give answers …",
    might do well to take the effort to understand the Wyler approach and apply it to get a deeper understanding of particle masses and force strengths.

    Tony Smith

    Hello Tony,

    nice to read you. I think these attempts might well be offering correct indicia, but it is quite hard to distinguish them from background noise... It's going to take the longer route. With Balmer it was immediately self-evident, but things are harder nowadays.
    will you like to read the article " feasibility of Bohr orbit quantization for multi-electron"

    Amrit Sorli
    How Higgs boson acts that "innertial mass" and "gravitational mass" are equal ? Is Higgs boson generating only "gravitational mass" or also "inertial mass" ?
    What is giving mass to the Higs boson itself ? 
    Is Higgs boson generating its own mass or there is some other particle generating its mass ? 

    Before we fully accept this model that Higgs boson is generating mass of the particles the 4 questions abowe need to be answered fully. 
    Amrit Srecko Sorli
    These four questions have been answered long before the discovery.

    You just need to do a search and read.

    On the gravitation side, not much has been answered if you include quantum gravity energies (planck energies). But that's completely separate from the four questions above.

    Tommaso, I'm not sure where you stand compared to AdS/CFT stuff, but if you believe that it could be a representation of a realistic theory, then there is no hierarchy problem for particle masses there, since they all start with similar parameters that evolve through an energy running that is very sensitive to initial differences. In that scenario, that problem is reduced fewer parameters.

    Then there are other approaches involving cross generation mixings or rainbow diagrams, but I'd assume those are the ones you'd include in a (non conclusive yet) search for a more fundamental theory.

    Dear Dan,

    I agree that the hierarchy problem is a problem only within a very specific framework. I personally view it as a hint that we are not thinking in the correct terms at the whole issue, rather than a inconsistency of the SM by itself...