What's the deal with God/Ghost particles?
September 17, 2008 2:25 PM   Subscribe

Will someone please explain to this non-physicist what the "ghost particle" is, and what the "god particle" is? Are they the same thing? How would one go about finding them (through LHC or other process,) and why are they so sought after?

Wikipedia isn't helping, and I'm getting a bit lost.

I'm also interested in any philosophical or religious questions/metaphors that might arise from searching for and/or finding these particles. I have a romantic notion of particle physics, please appeal to that side of the question and wow me with potentialities as well as explanations! In simple words, please-- I am a simple person.

Thank you!
posted by np312 to Science & Nature (5 answers total) 11 users marked this as a favorite
"The Higgs boson is infamous as the only particle predicted by the standard model of physics that remains undetected. In theory, every other particle in the universe gets its mass by interacting with an all-pervading field created by Higgs bosons. If the Higgs is discovered, the standard model could justifiably claim to be the theory that unifies everything except gravity."
From this good article at New Scientist magazine.
posted by lockle at 2:56 PM on September 17, 2008

Best answer: Excellent crash course at NYT
posted by mshrike at 3:04 PM on September 17, 2008 [2 favorites]

martinrebas, that is just absolutely excellent. I haven't got time to try to read the other suggestions right now, but I will later. Thank you lockle and mshrike for offering them.
posted by jamjam at 3:42 PM on September 17, 2008

Usually when people talk about "ghost particles" or "ghostly particles" they mean neutrinos. But that's just a name. Let's come up with some operational definitions.

Particle: if you can spray them, they're particles. Electrons are the classic example. You can spray electrons from a wire just by making it hot enough; if your hot wire is in a strong electric field, all the electrons get sprayed one way. This is how the big heavy cathode-ray tube TVs work: they spray electrons at the screen, and steer them with magnets. For fun sometime, wave a refrigerator magnet near a blue-screened CRT display. The extra magnetic field will steer the electron beam from the blue to the red and green pixels.

Electrons interact "electromagnetically." If you have a beam of electrons and you put some stuff in the way, after some thickness of stuff all your electrons have stopped.

There are other sorts of particles --- protons, neutrons, alphas, nuclei --- that interact "more strongly" than electrons. If you have a beam of alphas and you put some stuff in the way, all the alphas have stopped after a tiny thickness of your stuff. It turns out that this "strong interaction" is the same force that holds the nucleus together. Makes sense if you remember that nuclei are full of positively charged protons, which repel each other electrically; something stronger than their repulsion has to hold them together. But the strong interaction is short-ranged. This is why the periodic table ends with a group of marginally stable nuclei. In, say, a uranium nucleus, the protons on one side are electrically repelled from the protons on the other, but they are too far apart to be strongly attracted, so it doesn't take much of a push to break a uranium nucleus apart.

It turns out there is another short-range force that is weaker than electromagnetism, called "the weak nuclear force." The weak force can change a proton into a neutron, or an electron into a neutrino; this is beta decay. But if you had a beam of neutrinos and you put some stuff in the way, the neutrinos will only stop if they can change a neutron in the stuff into a proton. The odds of this happening are terribly small, and so neutrinos pass unimpeded through enormous thicknesses of stuff. The first neutrino detector used a roomful of detector material (it was dry-cleaning fluid, in a giant tank) and saw one neutrino a day, from the sun. But something like 2% of the sun's energy comes out in neutrinos. Nearly all neutrinos pass through the entire earth without stopping: only recently have solar neutrino detectors gotten big enough to tell the difference between day and night.

Open question: are there particles besides neutrinos that only interact weakly? There may be, and they have silly hypothetical names, like "neutralino" and "axion." So there may be other "ghost particles" besides the neutrino. How you tell one species of particle you can hardly interact with from another would take another long answer.

I don't care for the names "ghost particle" (or "God particle," though I didn't talk about the Higgs.) They're good names for selling books, and good overall publicity for high-energy physics, but they don't actually carry more information than any other name.

If you want to know more, ask; there are several folks with expertise in nuclear/particle physics reading.
posted by fantabulous timewaster at 5:03 PM on September 17, 2008

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