The news media are full of stories about the observation at the Tevatron of “single top” production, at a rate consistent with that expected from the Standard Model. There are talks at Fermilab going on about this today, and the papers are here and here. For an expository account, you can’t possibly do better than this one from Tommaso Dorigo.
While these results represent an experimental tour de force, they just confirm what is expected based on the standard model. Much more exciting would be if the Tevatron experiments can tell us something new about the Higgs and the Standard Model, and it looks like that may be coming this Friday afternoon, when a joint talk by the two experiments entitled “Higgs Results from CDF and D0” is scheduled at Fermilab. The two experiments have each collected about 5 fb-1 and started announcing limits on the Higgs based on analysis of up to 4 fb-1, but this is not quite enough for either experiment to be able to on its own exclude at 95% confidence level the Higgs at any particular mass. For this, one needs to combine the data from the two experiments. This was done last year, with results announced last August based on 3 fb-1 per experiment of data. This analysis allowed exclusion of the Higgs at 95% confidence level only in an extremely narrow range, basically just at exactly 170 GeV.
I’m guessing that what will be announced on Friday is exclusion of a Higgs over a much larger mass range. For a preview of this, see page 24 of the slides of a recent talk, where a graph shows what things would look like if you took twice CDF’s data set. This would come very close to excluding a range from 160-165 GeV, and perhaps within reach of excluding a region as large as 155-175 GeV, if not now, with only a moderate amount of more data and effort. It will be very interesting to see what they have…
For more evidence that this is what we’ll be hearing, Newsweek reports that:
This week scientists at Fermilab in Batavia, Illinois, will announce new data that not only narrows the gap between them and the coveted God Particle, but also suggests that the LHC may not be particularly well placed to make the discovery at all. The finding is a public-relations blow to the LHC and tarnishes Europe’s newly burnished image as a leader in Big Science….
The Higgs, the new Fermilab data show, does not exist for a portion of the upper range, putting it in the Tevatron’s cross hairs and suggesting that the LHC may be more peripheral to the search than previously thought. “We’ve made their jobs a little bit harder,” says Fermilab physicist Dmitry Denisov, “because we’ve excluded the region they’re good at.”
As the Tevatron shows that it can exclude the Higgs in the higher end of the expected mass region, where the LHC has a huge advantage, that means that either there is no Higgs (and presumably something else more interesting to find), or it exists in the lower part of the expected mass range (above the LEP limit of 114 GeV), where it is hard to find, but the Tevatron is not at such a disadvantage to the LHC. In any case, even if things work out as currently planned, the LHC will not start accumulating the kind of luminosity needed to compete with the Tevatron in this game until their 2011 run. It now appears highly likely that the Tevatron will be running at least through FY 2011 and possibly longer(for more about this, see here).