Slashdot Mirror
LHC Homes In On Possible Higgs Boson Around 126GeV
New submitter Ginger Unicorn writes "In a seminar held at CERN today, the ATLAS and CMS experiments presented the status of their searches for the Standard Model Higgs boson. Their results are based on the analysis of considerably more data than those presented at the summer conferences, sufficient to make significant progress in the search for the Higgs boson, but not enough to make any conclusive statement on the existence or non-existence of the elusive Higgs. The main conclusion is that the Standard Model Higgs boson, if it exists, is most likely to have a mass constrained to the range 116-130 GeV by the ATLAS experiment, and 115-127 GeV by CMS. Tantalising hints have been seen by both experiments in this mass region, but these are not yet strong enough to claim a discovery."
Unless things have changed since yesterday, the LHC cannot disprove the HB.
It can show that it isn't within certain energy ranges, but it does not have the capability of emphatically disproving it's existence over the entire predicted spectrum.
So far, so good, no one here calling it the God Particle yet. Lets keep it that way. Annoying as all hell.
http://en.wikipedia.org/wiki/Higgs_boson#.22The_God_particle.22
"Lederman initially wanted to call it the "goddamn particle," but his editor would not let him"
"Science flies us to the moon. Religion flies us into buildings." - Victor Stenger
The Higgs Boson is holding a press conference at midnight on Dec 24th. He's giving Christmas mass.
I was lucky enough to have a lunch hour where I could see the ATLAS results presentation.
The actual bump on the ATLAS graph was about 126 GeV, and the local sigma was 3.6 which is pretty good. The overall was only 2.4, which IIRC is about 95% certainty. I like the odds of finding it there.
I hate my flatmate
. . . all the way up . . .
Schroedinger's Brexit: The UK is both in and out of the EU at the same time!
the Standard Model become inconsistent with Higgs boson masses above 1.4 TeV, for example nonsensical total probabilities for certain scattering events greater than 100% appear (unitarity is violated)
As said at http://cms.web.cern.ch/news/cms-search-standard-model-higgs-boson-lhc-data-2010-and-2011, they have excluded 128 – 525 GeV at 99% confidence level. I am not sure they measure higher than 525 GeV with LHC for now. I would expect that existing theories for the Higgs put limits on its mass. Of course theories can be wrong, but if all theories about the Higgs are wrong, then there is no such particle.
One way to constrain the upper bound is with theory. The current Standard Model (without the Higgs) predicts that certain processes will start occurring more than 100% of the time at an energy of approximately 1TeV. The Higgs (or some other similar particle) fixes this problem but only if its mass is below a certain value.
The announcement today just narrows the mass. The /. summary is perfectly adequate, and is a complete summary of the situation!
There is also a small point, about a candidate mass just under 127GeV, with less than 3 sigma. The /. title is talking about that, but doesn't clarify it. Of course, some information with less than 3 sigma can change any time.
Rethinking email
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.
The fascinating thing about the energy they're talking about (125-126 GeV) is that it's too low. So low, in fact, that the equations predict vacuum instability at about that range.
What does vacuum instability mean? It means that vacuum might have a half-life, after which it decays into energy. This is a cool concept until you realize that the Universe is mostly made of vacuum. If the Universe were to spontaneously disintegrate, that would be Bad.
Of course since that doesn't happen, there must be new physics that keeps everything from fizzling out. That means that if the Higgs boson is found at 126 GeV then we're not done searching. There will be new questions to answer and possibly a new particle, the Higgsino, to look for.
Exciting stuff if you're a physics nerd. Or really for anyone who has a vested interest in the Universe continuing to exist.
Genocide Man -- Life is funny. Death is funnier. Mass murder can be hilarious.
The LHC is incapable of operating at the upper energies of the predicted spectrum of the higgs boson.....(this was known before construction even started)
Sorry but we certainly are capable of probing the ENTIRE allowed mass range for the Standard Model Higgs. The upper bound is ~1 TeV/c2 because at this level, without the Higgs boson, some Standard Model processes e.g. e+e--->W+W- "break unitarity" i.e. have a more than 100% chance of happening. Since this is clearly wrong it means that the Standard Model without a Higgs breaks down. Hence we only have to cover up to 1 TeV/c2 in allowed mass and either we find the Higgs or at least see a clear deviation from the SM and possibly see what causes that deviation.
There are ways to hide the Higgs, so-called "invisible Higgs" models, but these all require physics beyond the Standard Model. Also you can fit the existing SM parameters to find a prediction for the Higgs mass and this indicates that it should be below ~200GeV/c2 with a 95% confidence - although I'd take this with a pinch of salt. Now to get to the high mass range we will certainly need the full LHC energy i.e. 14 TeV. We currently have 7 TeV but this is NOT what the LHC was designed to run at - we are just limited to this energy due to the superconducting power bar problems. So to say that it was known that we cannot reach the upper energies before construction even started is simply wrong - the LHC was specifically designed to cover the entire energy range and, once we reach the design energy, we'll be able to do just that....although it is looking like the Higgs is there just at the low end of the mass range.
Can we have anti-grav vehicles, plasma swords and powered armor or not?