Re:How do they calculate the upper bound? (Score 5, Informative)

Looking for higher mass Higgs is easier than for this 120-ish GeV mass. E.g. if Higgs would be 150-200 GeV it would (via heavy vector bosons, which are 80-90 GeV) decay a lot into electrons and muons which are very easy to detect and see that they come from decay of Higgs. For 120-ish GeV Higgs, it decays mostly into two quarks and this is difficult to see because there are a *lot* of quarks flying around in proton-proton machine. So they have to use decays into two photons, which don't happen so often. Thus they need more time to discover Higgs of 125 GeV, than they would need for the one of 200 GeV.