Slashdot Mirror
Higgs Boson Detected?
Travis McGee writes "A scientist says one of the most sought after particles in physics - the Higgs boson - may have been found, but the evidence is still relatively weak. The Higgs boson explains why all other particles have mass and is fundamental to a complete understanding of matter. The report was published in Nature magazine and the BBC has an article." The last time the elusive particle was in the news was 2001.
According to this March 10 story at the Above Top Secret News Network, it is not actually news:
Posted by: Throwaway
On: Wed March, 10 2004 @ 20:33 GMT
This is old news, folks. Just signed up to tell you that BBC is recycling news stories to fill column-inches. I'm sitting on site a few hundred yards from the beamline. LEP shut down a couple of years ago, and there's been no real news since then.
My group works exclusively on Higgs searches and more or less leads the effort here on experimental analysis in that direction. Sorry.
9% is nowhere near close enough. And the BBC story is wrong - Higgs doesn't really explain where the mass of all particles comes from. And "the God particle" is a stupid marketing ploy for funding agencies. There's a lot more to go. Higgs has been the fundamental theory hole, not pivot. If we get one, it'll round things off nicely.
Stay tuned for 2007-2008 (9?)
In 1930 or so, Wolfgang Pauli noticed that in all interactions, this strange combination of variables (what we now call spin) stayed constant through those interactions. But he couldn't fully explain beta-decay, or when the nucleus of an atom spits out an electron ... this 'spin' wasn't conserved.
So, Pauli invents an incredible particle: it has little or no mass, hardly ever interacts with anything, but carries spin. It helped his equations balance.
Naturally, most of the scientific world scoffed at his idea at the time: it implied that hundreds of trillions of these things would be flying through space every second. AND they were undetectable?!? Quite a stretch.
But history bore him out, and neutrinos exist. You can see a history of the neutrino here, for more info, including current discrepancies with our understanding of neutrinos.
Quantum mechanics kinda developed the same way ... crazy math with weird conclusions went AHEAD of experiments, and those experiments bore out the math 5 or 10 years later. I believe the same approach is being taken for the matter in the universe (WMAP predicitons), as well as the higgs boson.
Just my 0.02 euro.
"Diplomacy is something you do until you find a rock." --Richard Pound
Here's a recent overview article on the status of Higgs in the LEP data (refinement and rehashing of stuff that's not really new anymore). Go to http://arxiv.org/PS_cache/hep-ph/pdf/0402/0402231. pdf
The total LEP experiment sigma comes out as less than two for a 115 GeV SM Higgs. That's not compelling. However, some VERY nice "gold-plated" 4-jet events were seen in the ALEPH detector, and it seems like there's a good chance that 115 GeV will be a good place to look in LHC.
Speaking of LHC, here's a webcam that lets you look at the ATLAS detector being built. :)
http://atlaseye-webpub.web.cern.ch/atlaseye-webpub /web-sites/pages/UX15_webcams.htm
If anyone (like me) needs a refresher on what the Higgs Boson entails from the perspective of physics, there's a nice collection of one-page explanations at http://www.phy.uct.ac.za/courses/phy400w/particle/ higgs.htm.
Again, these are two completely separate concepts. One makes things fly apart, the other helps keep things together.
Since the 1930's, it has been known that stars in galaxies orbit the center of the galaxy more quickly than they should, based on the visible matter. This requires extra "dark matter" to provide enough gravitational force to result in the observed rotational speed.That's not quite fair ... as a low energy effective theory, the SM is spectacularly successful, and is not in demonstrable conflict with any experiment to date. This success is underpinned by a reliance on a Higgs-like mechanism. The SM one-doublet model may be economical and incomplete, but because the rest of the model holds up so well to tests, it is hard to see how the correct model wouldn't necessarily have a SM Higgs-like excitation in the low energy limit. Which isn't to say that it will be exactly like the SM Higgs, just that it won't look too different at low energy, or we already would have seen its impact in precision eletroweak measurements, for instance.
it uses a scalar field ... of which there are no other examples in nature
That isn't quite a fair argument, of course ... we have no experimentally confirmed examples of fundamental tensor fields, either, but most of us think gravitons exist :-)
And there isn't a compelling reason to expect light scalar fields, in fact quite the opposite. You are no doubt aware of the quadratic renormalization of scalar masses, whereby their masses are "pulled up" by any interactions they have. So you probably wouldn't expect massless or even light scalars, unless they don't have any interactions (in which case we wouldn't know about them). In SUSY, for instance, you would generically expect scalars to end up with masses near the SUSY breaking scale, something like a few hundred GeV ... well, except for the lightest Higgs, which has to have a mass somewhere in the neighborhood of 100-200 GeV to stabilize the electroweak symmetry breaking transition.
This would allow much more complicated Higgs interactions...
There are plenty of examples of non-fundamental scalar Higgs mechanisms, and even mechanisms that employ fundamental scalars that must be heavier than we've seen. SUSY, dynamical symmetry breaking, extra-dimensions, deconstruction, etc. But they all have their own challenges, usually conflict with existing data. That, of course, is the cardinal sin in physics. No matter how lovely your theory, Nature is always right, and if you don't agree with Her, you lose. :-)
To nitpick, the "N=3" discovery is only valid in the energy range of interest.
To pick nits with your nitpick (how's that for a turn of phrase?), N=3 is the statement that there are no more SM like light neutrinoes, and hence there are only three generations of SM fermions. The precision Z boson line shapes from the four LEP experiments provide exceedingly severe constraints on weakly interacting fermions, and those line shapes are inconsistent with the presence of fermions that we haven't yet seen which are lighter than half the Z mass. In particular, the invisible line shape is consistent with more than 2.something and fewer than 3.somethingelse neutrinos, and since we already know that there are at least three, we conclude that there are only three.
It would have to have odd mixing angles, sure, but a fourth family isn't out of the question.
It would have to have VERY odd interactions with the SM gauge fields, to the point where it wouldn't look much at all like the rest of the SM families. There just isn't room in the precision electroweak data for much else that looks anything like the known SM fermions. In this sense, you probably wouldn't call this "fourth family" a family at all. Additionally, SM like interactions with heavy neutrinos are probably ruled out by cosmological over-closure arguments and astrophysical stellar models, although those arguments are somewhat more tentative.
There might, of course, be non-standard model like heav
Which isn't to say that it will be exactly like the SM Higgs, just that it won't look too different at low energy, or we already would have seen its impact in precision eletroweak measurements, for instance.
:-)
:)
:) I really need to create a new webpage...
:) And also, it's not like I have a better idea - I'm just skeptical. Lots of people can give me good reasons why a proton needs to decay, after all - and I'll still point to the >10^33 years measurement and say "Prove it."
Is that true? I didn't think the precision electroweak stuff depended too much on the pure Higgs interactions, but just on the symmetry-broken 'residual interactions' - i.e. the ones that gave the particles mass. I always find it hard to tell, though, as most books completely gloss over the Higgs physics sections because it hasn't been seen.
we have no experimentally confirmed examples of fundamental tensor fields, either, but most of us think gravitons exist
Well, we do have an experimentally confirmed example of a tensor field - gravity. That's what linearized gravity says - if you did have a spin-2 field, it'd generate gravity in the linearized limit. The important part is that the argument is reversible - you can say "what spin particle would cause these effects?" So we don't have experimental evidence of the particle, but we do have experimental evidence of the field.
The same isn't true for the Higgs field - you can't "reverse course" like you can with gravity, and take the interactions and work backwards to the dynamics of the particle. The easiest counterexample is technicolor, which would just as easily explain the Higgs interaction (ignore for the moment it also suggests other junk which is unobserved - it's unimportant to the argument). The point is that the scalar Higgs interaction does not uniquely predict anything. (As far as I know, no one's worked backwards from the fact that particles have mass and we see the interactions we do and said "only a fundamental scalar can cause this")
those line shapes are inconsistent with the presence of fermions that we haven't yet seen which are lighter than half the Z mass.
Yah, but I thought that restricted the heavier of the lepton family only (i.e. the electron-type) and not the lighter. Hrm, should go off and read the PDB section on that again.
But they all have their own challenges, usually conflict with existing data.
Ah, but doesn't a purely scalar Higgs conflict with existing data as well? We don't see one, after all. The excuse of saying "we haven't looked at high enough energies" seems to be exactly that - an excuse. I'll give the Higgs mechanism credit for being a "well-constructed theory" - a theory with enough flexibility in its parameters to avoid being disproven for quite some time. Like SUSY, for example (which I also don't believe is real).
The main reason that a simple scalar Higgs theory dominates now is because of the simplicity argument (and because it was first...), but I don't agree that having one fundamental scalar, and then everything else being more complex, is simple.
By the way, the link on your homepage to your research appears broken....
It is - that isn't my homepage anymore (I don't have a current one...), though my current research is here, if that web server's running.
Anyway, the funny thing is that I know all of the complications about the Higgs's existence - I mean, I've done the toy problem as to why it has to have the isospin that it does, etc. - but I still just don't believe that any particle that conveniently avoids discovery, and is the only one of its kind, has to be real. Note that I don't necessarily believe in a fundamental graviton, either.