The Tevatron's detectors, CDF and DZero, were only sensitive to a Higgs decaying into a bottom quark and bottom antiquark, which are "messier" to interpret, Strassler says. That mess prevents the detector from finding sharp signals of a Higgs at one specific mass, but it does allow researchers to see excesses over a range of masses.
Both saw signals that could be from a Higgs between 115 and 135 GeV at a level of 2.2 sigma, which is consistent with the LHC's results. "But until we get to at least 3 sigma, we don't use the word 'evidence'," says CDF spokesperson Rob Roser at Fermilab.
The LHC should have enough data to confirm or rule out the existence of the Higgs boson by the end of this year. But these searches are only for the most basic type of Higgs that the standard model allows. If the elusive particle never shows up, it could open the door to more exotic kinds of physics, including extra particles, extra forces and maybe even extra Higgs bosons.
Some physicists are hoping that's the case, if only because it would make things more interesting. "One Higgs would be very sad," says Nobel laureate Steven Weinberg, a key architect of the standard model in the 1960s.
Physicists have been writing theories based on the assumption that there is only one Higgs boson for decades, he says. But the standard model is already incomplete: it doesn't account for gravity or dark matter, for instance. "We've been living in a world with a Higgs in our theories for a long time, and we've gotten stuck. We don't see clearly what the road ahead is," he says. "If all we see at the LHC is one Higgs, it's not going to help us. We'll still be stuck."
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