Higgs Boson discovered?

[groza528]

So I know this is a big deal, but to be honest I'm not entirely certain why. I admit I haven't done as much research as I should before posting this thread and the news articles tend to be more more geared toward the general public... I have a science background, I just don't usually go smaller than electrons.

One thing that I've heard in the articles is that the Higgs Boson is supposed to explain why we have mass. I didn't actually know that mass was something we were confused about. Can some of you subatomic nerds *coughLepton* explain what's going on here?

http://www.bbc.co.uk/news/world-18702455

[MNOWAX]

best part of the articel was this:

[Trojan Horse]

groza: What IS mass?

[Jack_Ian]

I'm speaking from a layman's point of view, but here's how I understand it.
I'll presume you know the difference between mass and weight.
So the question becomes, what prevents things moving at the speed of light everywhere?
Imagine dropping a stone into water. The water provides resistance that prevents the stone from accelerating so that it eventually reaches something called terminal velocity.
In the same way, various particles encounter resistance to their movement and it is the Higgs field that was proposed to provide this resistance.
The Higgs boson is the particle that makes up the Higgs field in much the same way that water molecules make up the ocean.
Different particles react differently with this Higgs field and on the macro scale this appears to us as mass.

Also came across this, which you might find instructive.

[groza528]

Alright, but the ocean is full of water. And all matter has mass, so it would seem the Higgs boson would have to be pretty ubiquitous as well. And they say it "weighs" 133 times more than a proton (doesn't seem to be conventional weight, though? The point is it seems like it should be easier to detect than a proton.) So maybe I'm misunderstanding something here, but it seems like these things are pretty much everywhere and give off a reasonably strong signal... So why is it easier to create it in a lab rather than just find one somewhere?

Am I making a faulty assumption here? Are standard detection methods kind of a crapshoot for something so small, and they just made a whole mess of them so that they'd have a better shot at pinning one down and/or the signals would stack?

[raekuul]

In a clean lab environment, you can filter out everything but the HB and the filter (and you can logically filter out a uniform filter)

[Jack_Ian]

OK, this is where I'm bound to put my foot in it and display my ignorance, but that never stopped me giving my opinion before, so…

At a quantum level, not all matter has mass.
That's what was so confusing. Particles that resemble each other in many ways differ greatly in that one major respect.
And energy and mass are more readily interchangeable.

To get the mass of some non-elementary particle, such as a proton or neutron, you add the mass and energies of its constituent particles.

Saying that some particles had mass and others not, allowed a model of how everything interacts to be built that matched findings at that time.
When the Higgs field was proposed to confer mass to particles, various predictions were made that were since borne out by experimentation, and so there was great confidence that such a field existed and there was also a good understanding of the energy levels it might have.

The energy level predicted was expected to be large, and it would require a great deal of energy to produce.
Higgs bosons are being produced all around us by high-energy particles streaming in from the cosmos and colliding with our atmosphere, but since the Higgs field is ubiquitous, they are difficult to detect.

To explain what I mean, imagine you are a water-living creature at the bottom of the ocean. How would you you weigh water?

[Thok]

[Lepton*]

Good stuff from everyone. Let me give a bit of an orthogonal viewpoint. It is a bit too mathy for the NYTimes, but quite suitable for the GL.

In quantum field theory (that is THE theory) you write your model as the Lagrangian of a system. Each term in the Lagrangian (L) indicates how particles interact. Consider:

L = kLUU + mUU

This describes a theory with a particle U, which has a mass m (from the second term), and it interacts with another particle L with a interaction strength of k. L is massless, since there is no mLL term. If you've seen Feynman diagrams, the first term represents a vertex with two straight legs and one wiggly leg.

Of course, this is enormously simplified. The U and L are actually matrix-vector-functions, and the terms usually involve some strange version of multiplication, but hopefully you get the picture. Here is an example of a Lagrangian that (sort of) describes the Standard Model - [url] http://web2py.com/fermiqcd/static/images/sm.jpg[/url]

Now, the neat thing about the Higgs mechanism is that it allows you to get rid of all the terms like mUU in the Lagrangian and replace them with additional terms like HUU, where H is the Higgs Boston. The aesthetic appeal here is that the Lagrangian now describes only interactions between particles - all the properties of the universe (except gravity, so far!) can be derived from the strengths of interactions of the different fields, ie. the coefficients in the Lagrangian.

Visually, this is like a particle is traveling along, and then it emits and reabsorbs a Higgs Boson. Since we have to consider the sum of all possibilities in quantum physics, that means every particle is slowed down by emitting/reabsorbing, constantly. The Higgs itself is no exception, as it can emit/reabsorb itself; hence, it can have a 'mass' too.

It is hard to think of immediate practical applications. This experiment is important because of role the Higgs mechanism plays in the Standard Model Lagrangian. On the other hand, I am surprised there hasn't been much hullabaloo over the philosophical aspects of this (or maybe I should say psychological?), as it seems that mass -- that one tangible thing in life -- is no more real than energy or magnetic fields.

[Deception]

Forgive my amateur knowledge Lepton, but could you tell me if it is possible for a particle to absorb a Higgs Boson which has absorbed another Higgs Boson? That is, between the instant of one HB abosrbing another and that same HB emitting the second HB, could the first HB be absorbed by a particle - effectively placing two (or more, if we were to accept this) HB in the first mentioned particle?

Would the first HB be able to release another HB while in an absorbed state from another particle?

Again, thank you for your patience.

[Lepton*]

Yeah, all these things are possible. Any reaction you can imagine happening needs to be included in the calculations, unless it is impossible. Figuring out how to add up these infinite regressions was one of the biggest challenges faced by physicists when they developed the theory... but it seems they got it right, so far.

Impossible things: you cannot have an enter action that violates the conservation laws (momentum, charge, etc). Related to this, you can only have the interactions specified in the Lagrangian. Since the Standard Model doesn't have any terms like L = ... + UUUU + ... it is impossible for one particle to decay into three products simultaneously, for example.

[Zag]