Thursday, July 31, 2008

Tevatron favors light Higgs and MSSM

This is the very latest graph showing the top-quark mass (x-axis) and the W-boson mass (y-axis). The blue ellipse comes from the Fermilab:



You see that LEP I (CERN) and LEP II/SLD (CERN and SLAC) were undecided but the Tevatron (FNAL) seems to prefer supersymmetry: the blue Fermilab ellipse (68% confidence level) sits inside the green (MSSM) strip. That's surely not a reason to be 100% confident but it might be a hint. ;-)
See Pete Renton's PowerPoint presentation
Note that it is primarily the W mass that determines the expected Higgs mass and with the known data, the Higgs looks extremely light. The central value is below 100 GeV and at the 95% confidence level, the God particle sits below 154 GeV. When the direct searches are included in the calculation, the 1-sigma interval for the Higgs mass is 115-135 GeV. LEP could have discovered it if they could stop it later than they did.

95% percent of the Tevatron data are still waiting and it is expected that the precision of the W-mass (and other things) will be improved by a factor of three once all the data are processed. To make it clearer for some readers, using 20 times more data doesn't change their qualitative character: it only increases the accuracy by "reducing the noise", if you wish.




Incidentally, today, D0 at the Fermilab announced - in a press release - the discovery of three ZZ events extracted from 200 trillion events. ZZ events are very rare and somewhat similar to processes including a Higgs boson.

Via Tommaso Dorigo

5 comments:

  1. Sorry for posting out of subject, but I read a presentation you made at CEP 2007, where you said:

    "Water vapor is therefore not a “primary driver” of these changes but rather an
    immediate effect of changes in other “drivers”. "

    Is it really inconceivable that something, e.g. suns emissions, would be able to affect the precipitation efficiency and thus water vapour concentrations over prolonged periods of time? It seemed so plausible to me that I wanted to know why we can rule this out (if, in fact we can).

    Best,

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  2. Do we have a (preferably, string based) model able to explain why the yukawa coupling of the top is exactly 1 at low energy? AFAIK, no. This is the big failure of hep-ph in the last decade.

    True that Ibanez and other groups got to justify why it should be of "order unity", this is between 0.1 and 10. But we the current certainty of the value, the justification becomes too poor.

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  3. Absolutely, and I didn't mean that such things contradict my statements.

    In your case, the primary driver is the Sun, not water vapor. What I meant is that "water emissions" that people would add wouldn't play a role because water could be abruptly absorbed by the system, to reach the equilibrium value determined by the real drivers such as the solar parameters.

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  4. Arivero, sure. The top quark mass was predicted from string theory (free fermionic heterotic models) to be 175-180 GeV in 1991, years before the discovery. See Faraggi 1991. (Further corrections in his particular models, originally neglected by the author, would actually lead to a higher value, somewhat below 190 GeV.)

    But the value is natural from many other viewpoints. It is much harder to get hierarchically lighter 1st and 2nd generations but even this factor appears naturally in various stringy models.

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  5. Ah yep, indeed Faraggi and their corrections also do a good example of the same argument: that running down from GUT you can expect exact integers to happen within the order of magnitude, no within 1%.

    Really, the more I look into all this string stuff, the more it seems to be pure standard model at relatively low energy scale (1 TeV). Look at these web of dualities, bouncing between dimension 11, 9 and 6... the minimal dimensions of spaces supporting KK actions of SU(3)xSU(2)xU(1), SU(3)xU(1) and SU(2), respectively.

    ReplyDelete