Tuesday, March 01, 2011

CMS: Higgs not between 144 and 207 GeV if...

...a heavy fourth generation of fermions exists

The subtitle obviously makes the finding much less spectacular - because the fourth generation of fermions is unlikely to exist - and because the Higgs mass is probably below 144 GeV, anyway.

Nevertheless, it is impressive to watch how strong conclusions the LHC is suddenly able to produce. Based on 36/pb of the CMS data, the collaboration has published this preprint:
Measurement of W+W- Production and Search for the Higgs Boson in pp Collisions at √(s) = 7 TeV (plus press release)
They have studied the pair-production of charged electroweak gauge bosons and measured the cross section with the 40% relative accuracy or so.

That was enough to conclude that the Higgs boson mass can't be between 144 and 207 GeV in models with a fourth, heavy generation of fermions. This conclusion is possible to be made because with a heavy fourth generation, one increases the probability of the Higgs production via gluon fusion.

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