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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."
Knowing the mass of the higgs is important because it tells us which of our theories is on the right track. For example, a very large higgs would rule out huge branches of string theory, almost killing it. Not finding it at all would rule super symmetry would destroy the standard model, with nothing left to stand it in place.
The 'worst' case is that we find the higgs exactly where we expect it to be, confirming what we pretty much knew already, without adding any new real information.
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?
The electron volt is a measure of energy. It is the energy gained by an electron accelerating through an electric field potential of one volt. And since energy and mass are equivalent, this miniscule measure of energy also makes for a useful miniscule measure of mass.
If you mod me Overrated, you are admitting that you have no penis.
It's a unit of energy that particle physicists use instead of mass. One eV is an electron-volt which is equal to the energy gained by an electron after being sent through a one volt potential. You can use E = m c^2 to convert between energies and masses.
Not to diminish the importance of the work done at Fermilab, but the headline is very misleading.
eV is a measure of "energy", the E in E=mc^2
1 GeV = 1.783Ã--10^â'27 kg
When you're dealing with things that are really tiny, it's easier to use GeVs than 10^-27 kgs.
Okay, I only have a 4 year degree in Physics so maybe someone can help me out on this. If this particle gives the property of mass then shouldn't it have a mass less than that of the lightest particles? According to a quick Google calculation this thing out-masses an electron by 5 orders of magnitude.
WTF?
And 1 GeV = 1.783×1027 kg
Slashdot ate your formatting it looks like. I'll write it as 1.783E-27 kg to get around it.
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Cryptozoologists have narrowed down the possible habitat range of the Abominable Snowman. Spokesman for the research team, Dr. Justin Wanker, said "We've got him pinned down now!"
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That would be 10^-27 kg, a very small number, not 1027 kg.
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.
The SSC in Texas was 40 TeV, and the LHC at CERN will be 14 TeV when fully operational. They're about to turn on now, but will make their first run at the lower 10 TeV. Fermilab runs at 2 TeV.
Yes, we would have had the answers to all these questions and more 10 years ago, if the SSC hadn't been scrapped.
<soapbox>
The US is at a significant disadvantage when it comes to "big science". Every year, every project must come back to congress and beg for funding, justify their existence, rather than spend that time doing science. As a consequence, funding in the US is extremely volatile. Look at the budget crisis of DOE in December, the zeroing of the ITER budget, and the canceling of the SSC in 1993 for a few examples. Big science is worthwhile. We should figure out how to give scientists some measure of job security, so they can concentrate on science. This is a miniscule portion of the budget.
</soapbox>
1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.
GeV for mass seems odd. Why not use something more practical like percentage of mass of Library of Congress?
rewriting history since 2109
Actually is it not. Mass is correctly expressed in units of GeV/c^2. Einstein showed that energy and mass are equivalent with his famous E=mc^2 relationship. Hence mass, m=E/c^2. Thus we can use units of energy/c^2 to measure mass. This is particularly useful in fields like particle physics because we often convert mass into energy, or vice versa, and so it is useful to know how much energy it takes to create a particle (or is released in a particle decay).
Using units of 'GeV' for mass is actually very sloppy and technically wrong because energy and mass do not have the same dimensions and so cannot have the same physical units. The usual excuse is the use of natural units where c=1. However that '1' has dimensions associated with it and so to ensure that those dimensions are preserved you need to include it in the units. Hence mass is actually measured in 'GeV/c2' and not 'GeV'. Similarly momentum can me measured in units of 'GeV/c'.
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.
Occam's Razor would indeed say that, if it wasn't the case that the Standard Model is a very well tested model for particle physics.
The Higgs mechanism is part of the Standard Model. One of the predictions of this Model is that the quantum of the Higgs field, the Higgs boson, exists. Unfortunately, if it doesn't, it means something has gone seriously wrong with the model, because it's been successful in explaining a great many things.
While religious nuts are an easy scapegoat, that's not the problem. As I understand it, it comes down to the fact that no congress can bind any future congress. So no congress can set budget policy in any future year. They can make recommendations (and do), but this isn't guaranteed.
I don't think this problem is insurmountable. I would think that the creation of a certain kind of "scientific trust fund" could enable the use of a pot of money over a long time span.
1^2=1; (-1)^2=1; 1^2=(-1)^2; 1=-1; 1=0.
FAIL.
Try again.
They filled it with a ton of European magnets (that worked), Japanese detectors (that worked), and US final focus magnets (that failed).
Sorry to burst your patriotic bubble.
There's a great analogy for this which will probably help, http://www.hep.ucl.ac.uk/~djm/higgsa.html .
IIRC this was the result of a competition by Physics World (the magazine of the Inst. of Phys.).
> Am I the only one who sees a problem with the circular logic
Apparently, yes.
For one thing, it's "extra mass", not "mass". The mass of the electron is fully accounted for by it's self-energy. If you integrate the EM field energy over the electron's field, then apply E=mc^2 to that result, you get the right answer.
Higgs is only needed for particles that do not follow this rule, like quarks. Quarks are heavier than their otherwise obvious self-energy can explain. So we postulate another form of "charge" (sort-of) that these particles interact with. "Charges" are transmitted by mediator particles, so if we postulate a new charge, we postulate a new particle to go with it. And since that guy was Higgs, we have the Higgs particle.
The fact that the Higgs itself would have mass is not at all interesting, any more than saying it's circular to suggest that electrons are effected by electric fields.
Maury