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.

Comments

The boson kludge

[Curunir_wolf]

So, the standard model defines 16 particles. But if there are only those 16, then none of them have mass, so there must be another one, that magically provides mass for the others. Weird. You can't make this stuff up, folks... err... oh, wait.

Reminds me of the "dark energy" idea: "Well, we can only find 1/3 of the matter that we know should exist, so the rest is.. well, it's just the dark energy that we can't detect!"

Re:The boson kludge

[RobertB-DC]

The funny thing is this article in the "related links" section: 'God particle may not exist'

In that December 2001 article, we have statements like this: "Their conclusion is that there was nothing in the data at all to suggest the Higgs is out there - certainly not at energy masses of up to 115 Gigaelectronvolts (GeV), way past the level of 80 GeV where the boson was expected to show itself."

Contrast with March 2004: "Dr Renton cites indirect evidence taken from observations of the behaviour of other particles in colliders that agrees with the figure of 115 gigaelectronvolts for the mass of the Higgs boson."

The great thing, though, is how science done right is self-correcting. As soon as this boson was declared unlikely, researchers apparently began to attempt to prove that it did exist. Now that there's a theory that it exists, more researchers will begin trying to prove them wrong. Eventually, with all the facts out in the open, science will discover something approaching the ideal theory, which will likely be something unexpected.

It's like Microsoft vs. open source... find a bug in Windows, and it takes 9 months to patch it. Find a bug in Linux, and someone will patch it the same day...

(Obligatory disclaimer: I'm no physicist, and talk of "energy masses" and "gigaelectronvolts" makes my head spin. May as well be talking about Vitamegavegamin.)

Re:The boson kludge

[thermopile]

It's like the 'hunt' for the neutrino, and scientists have been following that methodology ever since.

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.

Re:The boson kludge

[Bootsy Collins]

So, the standard model defines 16 particles. But if there are only those 16, then none of them have mass, so there must be another one, that magically provides mass for the others. Weird. You can't make this stuff up, folks... err... oh, wait.

Nice try. Apart from the fact that the article's description of the role of the Higgs in generating masses isn't quite correct, there's your implication that this is some what frivolous. Well, if you evaluate scientific theories by the accuracy of their predictions, an argument can be made that the standard model of elementary particle physics is the most successful scientific theory of all time -- ranging from making correct predictions of electrodynamic phenomena out to absolutely absurdly large numbers of significant digits, to making predictions about the numbers of certain types of particles that will exist ("there will be one more light neutrino species, but no more after that") -- subsequently confirmed.

There are a lot of things you can fairly criticize particle physicists about; but suggesting that the standard model is removed from reality isn't one of them.

Reminds me of the "dark energy" idea: "Well, we can only find 1/3 of the matter that we know should exist, so the rest is.. well, it's just the dark energy that we can't detect!"

Like many people, you've got "dark matter" and "dark energy" confused (I personally hate the "dark energy" term, and wish Michael Turner (I think it was him) hadn't coined it; but we're stuck with it now). And while either of them may someday turn out to have been a wrong turn in the history of cosmology, neither is an unfounded concept.

Re:The boson kludge

[mph]

Reminds me of the "dark energy" idea: "Well, we can only find 1/3 of the matter that we know should exist, so the rest is.. well, it's just the dark energy that we can't detect!"

This statement is wrong in several ways.

First of all, "dark energy" has nothing to do with the missing mass problem. You meant to say "dark matter." Dark energy is another term for the cosmological constant, a parameter tied to the observed acceleration of the universe. There are completely independent measurements that require this parameter, including supernova acceleration studies and incredibly precise cosmic microwave background measurements.

Regarding dark matter, you seriously trivialize the situation. It's not a case of astronomers being unable to find the matter, like it's a lost set of keys. We see that galaxies and clusters of galaxies experience more gravitation attraction than they should, based on the visible mass. Hence "dark matter." But it's not just that we can't see it; big bang nucleosynthesis tells us that only a small fraction of the matter in the universe is baryonic. Baryons are the normal particles that "stuff" is made of, like you, me, stars, dust, and gas. That means that the missing mass is not simply something we're not seeing (because it doesn't glow, for example), but is something utterly different.

We're not missing mass because we're not good at finding stars, or dust, or whatever. We're missing it because it's something completely, fundamentally different from all of that stuff.

Re:The boson kludge

[JAPrufrock]

Hm. Go learn some of the math involved, and come back when you understand that there really are some compelling reasons for Higgs to come into the picture. Or are you aware of something that's been overlooked? You have a good reason that photons are massless and W/Z bosons aren't? Can you tell me why electrons weigh less than taus? Can you tell me how "mass" comes about? That plus the fact that the possibilities include standard model Higgs and SUSY Higgs, light Higgs, heavy Higgs, MSSM doublet Higgs, all in different variations... We didn't ask for all these particles to show up. We're just trying to figure out what we're seeing in nature.

Re:The boson kludge

[Curunir_wolf]

Ok, I'm confused (which you already pointed out!). "Dark Energy" (or the cosmological constant) is thought to explain the accelleration of the expansion of the univers, as you pointed out, since measurements of the microwave background radition indicate that there is no curvature to space. Since space is flat, that is, light travels in a straight line, there must be this mysterious force ("Dark Matter") driving the expansion.

Why is this completely unrelated to dark matter, though? What are the observations of "more gravitational attraction" that you refer to?

I thought the dark matter was required because the total mass of the universe (total amount of baryonic matter) was too small by about 2/3?

Re:The boson kludge

[njchick]

Regarding dark matter, you seriously trivialize the situation. It's not a case of astronomers being unable to find the matter, like it's a lost set of keys. We see that galaxies and clusters of galaxies experience more gravitation attraction than they should, based on the visible mass. Hence "dark matter."

You are contradicting yourself. It is a case of astronomers being unable to find the matter.

But it's not just that we can't see it; big bang nucleosynthesis tells us that only a small fraction of the matter in the universe is baryonic.

We know too little about "big bang nucleosynthesis" to make any conclusions, especially those predicting undiscovered forms of matter. We don't even know why we have more matter than antimatter.

Re:The boson kludge

[mph]

You are contradicting yourself. It is a case of astronomers being unable to find the matter.

No, I'm not contradicting myself. I was indicating that it's not simply being able to find something "normal," like a lost set of keys. The stuff we can't find is fundamentally different from normal "stuff."

We know too little about "big bang nucleosynthesis" to make any conclusions

Not true. The theoretical predictions of BBN, from particle physics, are in good agreement with observations of deuterium abundance, and the CMB power spectrum. You might not say it's rock-solid, but BBN appears to be generally sound.

Re:The boson kludge

[mph]

Since space is flat, that is, light travels in a straight line, there must be this mysterious force ("Dark Matter") driving the expansion.

No, this is the so-called "dark energy" that's driving the expansion. "Dark matter" acts through the gravitational force, to help keep galaxies and clusters bound. You were on the right track, until you suddenly wrote "dark matter" instead of "dark energy."

Again, these are two completely separate concepts. One makes things fly apart, the other helps keep things together.

What are the observations of "more gravitational attraction" that you refer to?

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.

Re:The boson kludge

[barawn]

there's your implication that this is some what frivolous.

I'd love to agree with you, but the Standard Model's Higgs mechanism has absolutely no authority to avoid the term "frivolous." In a lot of ways, it is.

The Higgs mechanism is done in the simplest way possible to generate masses - it uses a scalar field, which is the simplest field you can use, and, curiously, of which there are no other examples in nature - leptons and quarks are spinors (fermions of spin-1/2), photons/gluons are vectors, and even gravitons, if they exist, would probably be tensors.

There's no reason to desparately cling to the Higgs mechanism, other than we have no other way of generating mass that theorists 'like'. And, to be perfectly honest, this 'detection' does raise eyebrows - it's at the edge of LEP's detection, and it's only a 3 sigma (or so) detection. Now, that's not saying that Nature can't have been cruel to us and put the Higgs right at the edge of LEP's detection range, sure - worse things have happened. But it's a little suspicious.

Also, the Higgs "boson" has predicted nothing - anything that does symmetry breaking in a similar way would predict exactly the same thing.

(Sorry - I hate the fervent adherence to the Higgs, especially when we've looked, looked, and keep having to shove the mass up 'just a little higher' to the next accelerator range. I also hate the fact that no one else thinks that maybe a fundamental scalar just isn't possible for some subtle reason we don't understand. This would allow much more complicated Higgs interactions which people have typically ignored based on simplicity arguments. People said "if LEP doesn't find the Higgs..." and now people are saying "if LHC doesn't find the Higgs..." - what's next?)

("there will be one more light neutrino species, but no more after that")

To nitpick, the "N=3" discovery is only valid in the energy range of interest. You have to generate the lepton partner as well, so while the neutrino species could still be light, the lepton partner could be ungodly heavy, and thus outside of the detection field.

It would have to have odd mixing angles, sure, but a fourth family isn't out of the question.

Re:The boson kludge

[krlynch]

...the Standard Model's Higgs mechanism has absolutely no authority to avoid the term "frivolous."

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

Re:The boson kludge

[Alsee]

Vitamegavegamin

The correct spelling is Vitameatavegemin.

Vitameatavegemin contains vitamins, meat, vegetables and minerals. That's Vita-Meata-Vegemin.

Drumroll please, as we find out how old the moderators are.

-

Re:The boson kludge

[barawn]

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.

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. :) I really need to create a new webpage...

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. :) 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."

Different Name

[falzer]

They should have called it the bogon.

Re:Different Name

[SlowMovingTarget]

Actually I prefer weak grin bozon.

Well, OK, this particle is already named in the "Theory of Extra Special Relativity":

We start from the foundation of the dopeler effect: Stupid ideas that come at you rapidly seem smarter than they actually are.

Through our observations of individuals exposed to prolonged dopeler-shifted emanations, we can see that emission of dumb ideas tends to attract other dumb ideas, which in turn leads to a chain reaction of idiocy. All minds in the vicinity of high energy dolt fields are warped, consequently all conversations seem to take an infinitely long time.

Experimental evidence suggests that there is a limit to the density of weak grin bozon sources that any given region of space may sustain. Once this limit is passed, all thought in the region collapses in on itself to become a Quantum Imbecilic Singularity, from which no good idea may escape. QIS formations may be detected by searching for accretion disks of broken dreams, and massive jets of anticluons coming from a vector perpendicular to the back end of the accretion disk.

Nothing new here....

[menscher]

"May have been seen" and "evidence for" is a long shot from "discovered". Here's how it goes:

• less than 3 sigma deviation from background: ignored
• 3-5 sigma deviation: evidence for
• 5+ sigma deviation: discovery

At 9% chance he's wrong, it sounds like he's at around 2 sigma. Which is pretty much ignored by the scientific community. Which is why the LEP was shut down to make way for the LHC.

Not News

[Nynaeve]

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?)

but the evidence is still relatively weak.

[dpilot]

Groan!

Was the pun intentional?

The particle explains nothing.

[Anonymous Coward]

The Higgs boson explains why all other particles have mass

More correctly, the existence of the Higgs boson validates an assumption in a theory and theory is what claims to explain why all other particles have mass. The important thing to remember is that these are theories that are explaining things; real world particles explain nothing.

The real stuff

[JAPrufrock]

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

Re:The real stuff

[barakn]

Your links didn't work until I removed the extra spaces. Higgs Atlas

Useful resource

[omarius]

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.

Speaking of dark energy

[Maimun]

Speaking of dark energy, I wonder whether [suppose it exists indeed] dark energy does not break the law of conservation of energy. Once I attended a public talk by someont from Fermi Lab [sorry, cannot recall the name] who said that dark energy is a constant quantity [a very small number in standard units] per volume of space. So, given that the Universe is expanding and is being pushed more and more this way by the dark energy, the quantity of dark energy goes up and up, right? So, if it has indeed the meaning of energy, there is more and more energy in the Universe, contrary to the law of conservation...

Sadly, after the mention public talk only very few questions were allowed and I missed the opportunity to ask the expert in person.