Physics Stack Exchange is a question and answer site for active researchers, academics and students of physics. Join them; it only takes a minute:

Sign up
Here's how it works:
  1. Anybody can ask a question
  2. Anybody can answer
  3. The best answers are voted up and rise to the top

LEP II eliminated the Higgs up to 114.5GeV. If it had been run for longer could it have detected a Higgs at 125GeV?

I Googled for this without any luck, though I did find a comment that LEP II topped out at 209GeV collision energy, so it seems as though production of a 125GeV Higgs would have been possible. If so, how much longer would it have had to run?

share|cite|improve this question
As I recall both LEP and the Tevatron would have had to run a long time to extend their reach very far. I'm not making this an answer as I don't want to take the time to find a reference. – dmckee Feb 13 '12 at 18:05
I'll have to look up some info about LEP II but I'll try to take a crack at answering this soon... can't guarantee anything though since it is a busy week. – David Z Feb 14 '12 at 9:16
Thanks David, though it's not a burning issue so don't waste too much time on it. Obviously I'm wondering if there is some irony here and whether if they'd delayed decommissioning LEP by a year we'd have found the Higgs a decade ago. – John Rennie Feb 14 '12 at 10:41
up vote 19 down vote accepted

The LEP experiment's limits on the Higgs mass were set by looking for a process where the experiment would have produced a Higgs boson together with a Z boson. The highest energy they achieved for the electron-positron pair which annihilated to make Z,Higgs was 209 GeV, and that was only achieved in the last months of the experiment. Since the Z boson mass is 91 GeV, the highest energy Higgs boson which could be produced this way would have a mass of 209-91=118 GeV. Some of the energy is always lost to getting the Z and Higgs to move apart from each other, so in practice the limit they could achieve was a little lower than this, 114 GeV. By running much longer and accumulating statistics they could have extended their reach a little bit, perhaps to 116 GeV; but not to 124 GeV. That could only have been achieved by significantly increasing the energy of the beams -- which I believe they had already pushed as far as they could.

share|cite|improve this answer
A look at the "ALEPH HIGGS" which was published in "physics letters" shows how the analysis was done, as far as numbers go – anna v Feb 21 '12 at 18:58
Ah, thanks Guy and Anna, that's very clear. – John Rennie Feb 22 '12 at 6:38

Your Answer


By posting your answer, you agree to the privacy policy and terms of service.

Not the answer you're looking for? Browse other questions tagged or ask your own question.