The Race for the Higgs

By Sean Carroll | February 17, 2009 4:42 pm

The Large Hadron Collider should be lurching back to life this year, but the Tevatron at Fermilab might yet have a last hurrah. While the LHC is still fixing itself after last fall’s explosions, the Tevatron has been collecting data like mad, and hopes to continue for another couple of years. At the American Association for the Advancement of Science meeting in Chicago, Fermilab scientists said they have quite a good shot at collecting “evidence for” (although not quite “discovery of”) the Higgs boson before all is said and done.

Adam Yurkewicz at US/LHC Blogs has the scoop, and you should go there for more info. But this graph tells the basic story. It’s the probability that Fermilab will be able to find “three-sigma” evidence for the Higgs, depending on what its mass is, if the Tevatron gets to run through 2011.


Due to complicated background events, finding a particle like the Higgs isn’t just a matter of smacking together protons and antiprotons at higher and higher energies. Some possible values of the Higgs mass make it easier to find than others, since the reactions that produce it aren’t as swamped by boring known events. That’s why the Tevatron has a shot, even if LHC opens with substantially larger energies later this year. The BBC story portrays the whole thing as a race, which is fine, but to the rest of the world it’s more important to just find the darn thing than which continent gets there first. (Given that the Higgs is a boson, the smart money would seem to be on Europe.)

  • TimG

    The webcomic Abstruse Goose has a message for the Higgs boson.

  • TimG

    By the way, is it possible to create this sort of plot for the probability of the LHC finding the Higgs over some specific time frame? (I know everyone expects the Higgs will show up sooner or later.) If so, has anyone done it?

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  • erik

    I don’t quite get how the probabilities are calculated… How do you get a 70% probability of textit{evidence} inside the LEP textit{exclusion} zone?

  • Sean

    erik, that’s just the chance they would have had of doing that well, if LEP hadn’t already excluded that region.

  • Brian Mingus

    A person that wanted to win a race would skip $latex 120-150 GeV/^2$ and come back to it later if necessary, no?

  • Martin

    Brian: the x-axis of that plot does not show what energy they are working at, but rather what the (unknown) mass of the Higgs is. Assuming we are restricted to only one Higgs and only one universe, they don’t have an option to skip parts of the plot…

  • per

    Hi Sean,

    So 3sigma is considered evidence for? What is considered as a discovery?

    Thanks for the blog, P


    Oh, silly me for not recognizing that gigaelectron volts over the speed of light squared is equal to kilograms!^2

  • graviton383

    For a discovery, 5 sigma is the usual requirement.

  • Count Iblis

    If Fermilab and the LHC both have 4 sigma evidence then combined they’ll have more than 5 sigma evidence which would count as a discovery.

  • existential mime

    Count Iblis Says:
    “If Fermilab and the LHC both have 4 sigma evidence then combined they’ll have more than 5 sigma evidence which would count as a discovery.”

    Even with the most optimistic assumptions, the combined CDF/DO data set has projected a no more than 50% chance of seeing even a THREE sigma anomaly in the region most favoured by the electroweak radiative correction fits (ie. not much above the direct LEP limit, and where LEP itself has already seen an “indication” at just under 3 sigma). When ATLAS and CMS have between them a solid five sigma discovery to announce, then the papers will come out [I’m willing to bet that you can count on CERN management to enforce this much self-discipline}, and then we’ll know.

    Is it really worth spending many tens of millions of dollars to add the Tevatron to LEP on the list of “indication but not able to really say anything definite” accelerators that were unable to either discover or definitively rule out the Higgs, or would that money be better spent planning and preparing a future for Fermilab that lasts longer than the next two years? I see this recent round of Fermilab publicity as more an admission of real concern about the prospects for “Project X”, than as useful information concerning prospects for an actual Higgs discovery.

    P.S. There are a hell of a lot of americans working on ATLAS and CMS. In fact there are more american CERN users than there are of any other nationality. So the Higgs discovery will in a very real sense be an “american discovery” (shared with other nations), even though it will almost certainly actually occur at CERN.

  • Reginald Selkirk

    I’ll bet if everyone on the planet checked under their sofa cushions today, the Higgs would turn up somewhere.

  • John
  • MedallionOfFerrit

    Reginald! It was there, under the left-most cushion! How do you want to be credited in the paper? You theoreticians are so useful to us experimentalists. See you in Oslo!

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  • changcho

    Doesn’t matter who finds it first (but do find it!): but please, stop calling this thing the ‘god’ particle – what a stupid nickname.

  • Sili

    Yeah – it’s the Goddamn particle. Get it right.

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About Sean Carroll

Sean Carroll is a Senior Research Associate in the Department of Physics at the California Institute of Technology. His research interests include theoretical aspects of cosmology, field theory, and gravitation. His most recent book is The Particle at the End of the Universe, about the Large Hadron Collider and the search for the Higgs boson. Here are some of his favorite blog posts, home page, and email: carroll [at] .


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