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Q & A: Higgs boson and Higgs field

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Most recent answer: 02/18/2013
Q:
1. If Higgs field exists everywhere and it interacts with matter to give mass, why do we need high energy collision (LHC) to produce Higgs Boson? 2. And if Higgs boson decays to other particles, how can it interact with other matters to keep producing mass?
- waiming au (age 55)
Portland, OR
A:
The key here is to distinguish between the Higgs boson and the Higgs field. The Higgs field is a background field with which many particles interact. The interaction has some energy, which is equivalent to the rest mass of the particle. There would be big problems for particle theory if no form of the Higgs field existed. 

Particle theory doesn't need the Higgs boson directly, but it comes along as an inevitable consequence of the Higgs field. You can think of it as a sort of propagating ripple in the field. Even when it decays to other types of particle waves, the background field persists.

Mike W.

(published on 07/09/2012)

Follow-Up #1: gravity's boson

Q:
Higg's field is what causes fermions to have rest mass and the Higg's boson is the medium of that interaction between fermions and the Higg's field. So far so good, all is well. Well, how in the world a fermion interacting with the Higg's field results in fermion distorting space-time. In other words, how to you connect Higg's field with GR. Is there an undiscovered boson that causes particles with rest mass to distort space-time?
- Anonymous
A:
Yes, the name of the as yet unobserved boson connecting gravity (space-time distortion) with mass is the graviton. Don't expect them to be detected as quantized particles anytime soon.

It's important to realize that rest mass is not required for spacetime distortion. Anything with an energy-momentum 4-vector will do it, e.g rest-mass-less photons,


Mike W.

(published on 07/17/2012)

Follow-Up #2: Higgs field and boson: which came first?

Q:
What existed first, the Higgs Field or the boson? What is the relationship between the two, does the field interact with itself to create the boson (is this the only way that the boson came into existence), or does the boson somehow exert a field?
- Emma (age 19)
Australia
A:
The answer will be that the Higgs boson is a sort of wave in the Higgs field. You could have the field without having any of the bosons around (in fact, it's hard to get them) but the field sets up the possibility of their existence.

Let me try to explain this with a story about something that's easier to picture.

Look at a warm piece of iron. There are little magnetic fluctuations throughout it, but no organized magnetic structure. When it cools down enough (below what's called its Curie temperature), the little electron magnets pick some accidental direction and mostly line up pointing the same way. Ideally, at zero temperature, they all line up as much as their quantum nature allows. At any rate, once they start to line up there's a systematic magnetic field which wasn't there before, in one direction. In the plane at right angles to that, there's no systematic field.  That's like the Higgs field, something that forms from a more complicated field when the universe cools down. Just as one direction of magnetic field becomes different from the others, one "direction" of field in an abstract space, not ordinary directional space, becomes a special field, the Higgs.

You can picture the lined up magnetic field as a collection of magnetic field lines, like strings under tension. One of the things they can do is stretch a little to the side, like strings, with waves propagating along them, like sound down a string. These waves are called magnons. So the magnons are wiggles away from the ideal lined-up state. You can't get magnons until some sort of lined-up state is there to begin with. There are different types of magnons traveling along the field and at right angles to it.

The Higgs particle  is a sort of wiggle in the more abstract space, a type of wiggle that can't be there until the Higgs field forms. There are other types, (called W and Z) in other abstract "directions", like magnons not along the field direction. Back in the day, before the Higgs field formed, all these W, Z, and Higgs effects were jumbled together in one sort of fluctuation, like all the little magnetic fluctuations in all directions in iron above its Curie temperature.

Mike W.

(published on 02/18/2013)

Follow-up on this answer.