So today the NYTimes says Fermilab has further evidence of possible evidence of the Higg’s Boson. Higgs Boson May Be Indicated in New Data - The New York Times Note that the proton is about a billion electron volts, and the “bump” is around 125 billion electron volts. Can anyone explain to us physics lay folks why a particle 125 times more massive than a proton has been so difficult to detect? Is a proton more stable by itself, and the Higg’s Boson so very unstable? What determines stability?
Or did I just ask for a graduate seminar lasting two semesters?
It’s hard to detect because it just doesn’t sit there and let you examine its properties. As you guessed, it’s not stable and decays. The decay products have to be detected. And before you can do that you have to produce it, which requires that you get some particles up to high enough energy so that they’re more energetic than the Higg’s. Then you slam them together and hope one of the collisions produces a Higg’s for you to detect.
Heavier particles decay into lighter particles if such a decay is allowed. The proton probably is (or perhaps we’re down to “may be” now) because there there is no lighter hadron that it can decay into, and “hadronness” probably has to be conserved. The electron is stable because there is no lighter negatively charged lepton for it to decay into and charge has to be conserved.
I’m probably going to regret poking my nose in here, but sometimes you learn a lot in the process of getting your virtual ass kicked. :eek:
+1 to OldGuy. I would just add that the Higgs doesn’t have to actually exist - outside of Fermilab anyway. I’m not sure if there is any consensus on that though.
What’s important is the Higgs field. Apparently that can exist with nary a boson in sight. As my imperfect understanding has it, each of the 4 forces - electro-magnetic, weak nuclear (responsible for radioactive decay), strong nuclear (binds protons and neutrons in the nucleus) and gravity - has it’s own gauge field which is responsible for the action of that force.
I’ll stop there since the slope is feeling slippery.
Please explain the Higgs boson to this layman. If of course, such a thing is possible. I read the Wikipedia page but it left me still a bit confused.
In particular:
How does it give other particles mass?
The wiki says it has something to do with the Higgs field. I would hazard to think the field is generated by Higgs bosons - but every particle has a consistent mass so…
Other fields seem to vary based on where their contributing particles are (electric, magnetic) but if the Higgs field is all pervading and uniform that implies some sort of universal matrix of uniformly spaced Higgs bosons. What gives?
How exactly does it interact with other particles?
It has it’s own mass. How does it interact with itself?
It’s greatly more massive than other particles. How does it impart a smaller mass than itself on other particles?
The Higgs boson isn’t just floating around space waiting for us to detect it. It is unstable, so none exist unless we create them in the lab. Its mass is the very reason it is so difficult to detect, because it makes it hard to create it. The way we create it is by colliding particles in a particle accelerator. Unfortunately, when you collide particles, you create lots and lots of particles, not just the Higgs boson. So for every few Higgs bosons you produce, you create millions of other particles, some of which look very similar. So finding the Higgs boson is like looking for a needle in a haystack. It can be done, but it takes a lot of work!
The proton is stable by itself, and the Higgs is very unstable. The proton is stable because it doesn’t have anything lighter than itself that it can easily decay to by following the laws of physics. The Higgs is unstable because there are a lot of lighter particles that it can easily decay into.
Think of it like this. Take a photon. It has no mass. Is there any way we can make a photon “look” like it has mass? Yes! Imagine every time the photon moves some tiny distance, something reflects it backwards, like a mirror. So the photon is bouncing back and forth, like it is surrounded by a tiny spherical mirror bubble. Now this photon “trapped in a bubble” is sitting still, with zero velocity, because it is just bouncing back and forth around the same location. Suppose you push on the bubble. What happens? As you push the bubble, the photon pushes harder against the wall of the bubble, making it difficult to move. But once you stop pushing, the bubble continues moving with a constant velocity. In other words, the bubble has inertia, and acts exactly like it has mass. The mirror/bubble in this example is the Higgs boson, which is constantly interacting with the photon, reflecting it back and forth, making it act like it has mass. In reality the photon doesn’t have mass, because it doesn’t interact with the Higgs boson. But this is the way the Higgs boson gives mass to particles like the photon.
No, this just implies a Higgs field pervading all of space, like you said. The Higgs field is different from the other fields you are used to, because it has what is called a non-zero vacuum expectation value. This basically means that you have a field filling all of space without needing Higgs particles everywhere acting as sources for the field.
Like I described above, it causes them to zig-zag back and forth at a microscopic level. The Feynman diagram looks like the letter Y, with two of the legs your particle, and one of the legs is the Higgs. So you have a particle moving along, and the Higgs particle is constantly giving it little “kicks”.
It gets its own mass by interacting with itself, no biggie! Again like the letter Y, where all three spokes are the Higgs boson. Again it is moving along, and a Higgs keeps coming along and giving it little “kicks”.
One thing to make clear is that “a Higgs particle” is not what gives particles mass, but technically the Higgs field. The Higgs field does this by exchanging virtual Higgs bosons, not real Higgs bosons (the same way that the electromagnetic field is mediated through the exchange of virtual photons). When I say “Higgs” above, I’m referring to virtual Higgs bosons that mediate the Higgs field.
Because the way it imparts mass doesn’t have to do with how massive it is. It has to do with how often the Higgs field interacts with a given particle. If a particle really likes to interact with the Higgs field, then it is more massive. If a particle doesn’t really like to interact with the Higgs field, then it is lighter.
Like you, I don’t really know what I’m talking about, but I think you slipped up here. The weak nuclear force binds protons and neutrons in the nucleus and is responsible for radioactive decay. The strong force binds quarks together into protons and neutrons.
To the OP, the more massive a particle is, the harder it is to make in the lab, not easier. It’s easy to smash rocks together and get powder. It’s not easy to get them to come out in big chunks. For that, you’d need bigger rocks to start with and therefore bigger cannons. Then you’d have to try for a long time while each pair of rocks keeps making, say, ten or twelve small chunks instead of the two big ones you really want. Eventually you’ll get your two big chunks, but the cannon wasn’t cheap and you needed a lot of gunpowder to get there.
Sure — right after the Big Bang. At that point, the Universe was much hotter and denser, so particles were moving around a lot faster and smashing into each other just like they do at the LHC, so there would have been Higgs bosons created in much the same way. Of course, they would have been unstable back then too, decaying away just as quickly as they do now. But back then there were always more being created, since all the particles had much more energy.
To add to this: experiments have been done that say that the half-life of a proton is greater than 10[sup]33[/sup] years. Note that this is hugely greater than the current age of the Universe (about 10[sup]10[/sup] years.)
We know, from the existence of high energy cosmic rays, that there must be some very powerful astronomical particle accelerators in nature, probably supermassive black holes. So nature may create a few Higgs bosons from time to time, but again, they are unstable, and decay in less than a nanosecond. So they wouldn’t “exist” for very long. They same is true for the W and Z bosons. Virtual W and Z bosons “exist” while mediating the weak interaction, just as virtual Higgses “exist” while mediating interactions with the Higgs field. But you need very high energy density to create real W, Z, or Higgs bosons, and then they decay immediately.
Certainly sometime during the first second of the big bang the energy density was high enough for there to be some Higgs bosons around.
I’d also imagine that more than a few cosmic rays have enough energy to toss off a higgs on occasion when they hit the atmosphere. Maybe some in accretion disks around around black holes, &c.
It’s the “Higgs boson,” not Higg’s boson. It was named after Peter Higgs. The apostrophe would indicate it belongs to some guy named Higg (which I think Patty was poking fun at in post #2).
The Higgs mechanism gives things *inertial *mass – i.e. resistance to changes in velocity due to application of force – it’s still not a theory of gravity.
At the risk of sounding like those guy in the other threads who resolutely don’t believe in relativity, or spherical earth, or Obama being American or whatever: I’m lost here.
I’m not following what the Higgs boson has to do with the Higgs field. Everyone is saying the boson (or is it the field?) that imparts mass. Everyone is saying the boson is very rare and very short-lived. But there are things all around me that seem to have mass, and they are very stable. And to mediate the field, it’s the virtual not the real bosons that are doing that.
So why the interest in a Higgs boson? Does it really serve any purpose of interest to physicists? Or is it just an occasional incidental artifact, the occasional appearance of which serves only to verify a prediction of the Theory? (Damn! It’s hard to even formulate an intelligible question, I know, when the subject is Quantum Anything and you’re a stark raving layman!) Is my question even remotely coherent?
ETA: I kinda liked this theory, which someone posted as a comment to a Yahoo news article last December:
My theory is that the Higgs boson in fact exists… but there is only one of them. (Note how the article consistently refers to it in the singular). It circulates unimpeded at random through all the particles in the universe, dispensing mass to each one. The probability that it will get caught up in someone’s particle accelerator and detected is vanishingly small. See: Yahoo's Teaming Millions weigh in on Higgs Boson! - Cafe Society - Straight Dope Message Board
Cure my ignorance, then- I thought the residual strong force was the weak nuclear force. I thought the strong force, mediated by W and Z bosons, bonded quarks to each other to create the protons and neutrons, while the residual force between bound protons and neutrons to each other to make nuclei. I thought this residual force was called the weak nuclear force.
The strong force is mediated by gluons, and binds quarks into hadrons. It also binds protons/neutrons into nuclei, but is “weaker” because it is a residual effect of the strong force (protons and neutrons are neutral under the strong force), just like the Van der Waals force in electromagnetism. Note that there “weak” is used as an adjective rather than the name of the force itself. The “weak force” is totally different. It is mediated by W/Z bosons, and its only major role in nuclei is in causing nuclear beta decay.