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First Definitive Higgs Result In 7 Years
PhysicsDavid writes "In a suite of new results about the Higgs boson, Fermilab presents the first new definitive evidence on the (lack of) existence of the Higgs boson since the Large Electron Positron collider shut down in 2000. Fermilab hasn't found the Higgs, but can rule out a certain range of masses for the particle that is believed to create mass for all the other particles of nature. Other Higgs news suggests a new likeliest mass range of 115 to 135 GeV for the Higgs. These results were among those presented at the ICHEP 2008 conference currently wrapping up in Philadelphia."
Don't joke about that, I'm sure I read about a paper last year which predicted a minimum Higgs mass just outside of the LHC's range. It must keep those involved awake at night.
No kidding!!! What do you say at this point?
It sounds like you're thinking about the Higgs giving mass to particles by being a constituent of them. (That is a perfectly reasonable linguistic interpretation of ``give mass to'', but it doesn't reflect the physics.)
In these theories, mass arises of interactions with the Higgs boson. Thus, the Higgs being massive doesn't exclude less massive particles.
actually when I first heard about it, I thought it was a fermilab discovery. Theres been a lot of rumors flying around that CDF had something big. If this was it, I'm disappointed. Also for the record, fermilab is still very relevent. The most likely place for the Higgs given current experimental evidence is in the second easiest place for the Tevatron experiments to see it (115 GeV) but the hardest place for the LHC experiments to see it. So the Tevatron could well scoop the LHC, its not over.
Incidently, why is 115 GeV so hard for the LHC to see. Well at this point the Higgs is too light to decay to WW or ZZ (the W has mass of 80 GeV, Z 91GeV so needs Higgs mass of 160-180 GeV to open those channels). This means that a light Higgs of 115 GeV will decay into the heaviest particle availible to it (remember the more massive the particle, the strong the Higgs coupling) which is the bottom quark. At the Tevatron, the backgrounds to two bottom quarks isnt soo bad and the experimenters are all very experienced at tagging b quarks using their detectors. At the LHC you might as well give up so you have to go through the very rare vector boson fusion channel using a top quark loop to get two photons which itself has a bit of nasty background. Hence you will need 10 fb-1 of data which is *atleast* a years running at the LHC.
At the Tevatron, the backgrounds to two bottom quarks isnt soo bad and the experimenters are all very experienced at tagging b quarks using their detectors.
Actually the background for b quarks at the Tevatron is ENORMOUS. b-quarks are produced by the strong interaction at rates far higher than they are produced from any possible Higgs decay. Identifying them is only half the problem: determining what produced them is the other half! The only way that we can see anything is via associated production of a Higgs and a W or Z boson (which are a lot easier to spot). This is a far rarer process than simple Higgs production.
At the LHC you might as well give up so you have to go through the very rare vector boson fusion channel using a top quark loop to get two photons which itself has a bit of nasty background.
You are actually a little out of date here. While the vector boson fusion channel is still used the decay is actually Higgs to two taus or VBF Higgs production with the two associated quarks being top quarks. At least in ATLAS we think that both of these channels will have a higher significance than the photon channel which was the original choice for a low mass Higgs.