Wednesday, March 02, 2011

Higgs By End of 2012, Or Else.....

In my blog entry on the issue surrounding the missing SUSY particles at the LHC, I mentioned a news article regarding the same looming "deadline" facing the search for the Higgs.

If the collider does not detect the Higgs within two years, researchers say they will know that it does not exist - at least in the form required by the Standard Model, the framework which was devised to explain the behaviour of fundamental particles.

"The Higgs is one model of many," according to Professor LeCompte
"If we don't see it after this two year run it means that something is perhaps not the way that we think it is, either the Higgs search itself had to be amended in some way or some of its indirect evidence may be pointing us in the wrong direction," said Professor LeCompte.

After I read that, I had a slight puzzle in my head. The LHC will be running at 7 TeV till the end of 2012 when it will undergo a long shut down to make the necessary electrical repairs. It will then go back online at the nominal design energy of 14 TeV. Presumably, at the higher energy, one expects that it should be easier to spot the Higgs signature. So I was wondering if Tom LeCompte might be a bit premature in expecting the Higgs to show up before the energy upgrade. So I asked him! This is the reply I got back, which I'm posting here with his permission:

The LHC will be at 7 TeV this year, and 7 or 8 TeV next year. Since protons are not elementary particles, we get a broad-spectrum beam of quark energies, so are sensitive to many different masses at once.
(Unlike an e+e- machine where you often have to scan energies)

The Higgs has to be above about 110 GeV, otherwise it would have been discovered earlier and below about 1 TeV, beyond which it is too heavy to have a role in EWSB (which is why it was postulated in the first place). Precision electroweak fits suggest that it's on the low end of this range. The LHC in 2012 can discover/rule out a Higgs on the low side. If we don't see it at 7 TeV, and do see it at 14 TeV, we have a problem with the precision electroweak data.

Well, there you have it.


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