Talk:Baryon
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My references say that baryons are elementary particles, they consist of quarks and cannot be broken down. Mesons also fit this description.
Two web sources for you to examine - [1] (http://www.infoplease.com/ce6/sci/A0857949.html) and [2] (http://www.infoplease.com/ce6/sci/A0806361.html)
Also my dictionary says:
Hadron Pronunciation: (had'ron), [key] —n. Physics.
any elementary particle that is subject to the strong interaction. Hadrons are subdivided into baryons and mesons. Cf. quark.
All the sources I've seen don't call baryons as elementary particles, because they are composites, even if they can't be physically ripped apart. I would guess the usage varies, and so suggest that they not be called elementary.
Give some citations - I'm sure we can sort it out. I've given three, but I acknowledge that they are all quoting generalist literature. By the way, the link to boson simply redirects to particle physics... surely they deserve their own article. - MMGB
- Elementary refers to any particle which is not composed of smaller particles. "Broken down" is not meant in a physical sense. There are exactly 16 elementary particles known to date: 6 quarks, 6 leptons, and 4 gauge bosons (not including antiparticles or gluon flavors). The jury is still out on the Higgs boson and the graviton. See http://www.neutron.anl.gov/hyper-physics/Particles.html for a good diagram -- Xaonon
Well I guess this is a case where infoplease got it wrong - some other sources I have checked confirm this position. If/When we have an article on elementary particles this confusion should be addressed directly.
Someone mentioned that mesons may be a superposition of quark-antiquark pairs, but I think it would be less confusing and more accurate to describe them as a pair where each of the quark and antiquarks may be in a superposition of states (colors and generations). Does this sound fair?
Does anyone know the mass of a baryon? Is it just the mass of a proton? or neutron? --PY
- It varies between different types of baryon. If a specific baryon is a proton, then it has the mass of a proton; if a neutron, then it has the mass of a neutron; and so on. -- Paul A
PY, I believe that you are assuming that the baryon is a particle when it is actually a classification of particles. There are dozens of different baryons, each with its own mass.
Keep in mind that there was not a general consensus that hadrons were made of quarks until the mid-1970s. Older references could well describe them as elementary particles simply because their constituents were undiscovered or not generally accepted; even today they are sometimes called elementary particles because of a kind of language inertia. But we probably shouldn't call them that. --Matt McIrvin 00:29, 1 Oct 2004 (UTC)
Include table?
This article lacks a table summarising the properties of the mentioned baryons. Obviously a comprehensive table of known baryons would be a bit too large for the article. :) But something like this might be nice: http://hyperphysics.phy-astr.gsu.edu/hbase/particles/baryon.html
A mention of the quantum numbers associated with baryons would be nice as well. (Baryon number, strangeness etc.)
Here's a first attempt, perhaps someone can check that there are no errors in it? (Either of fact or of format :) ). It includes all of the baryons mentioned in the article, in the order mentioned.
| Particle | Symbol | Makeup | Rest mass MeV/c2 | B | S | C | Mean lifetime s |
|---|---|---|---|---|---|---|---|
| Proton | p | uud | 938.3 | +1 | 0 | 0 | Stable1 |
| Neutron | n | ddu | 939.6 | +1 | 0 | 0 | 920 |
| Delta | Δ++ | uuu | 1232 | +1 | 0 | 0 | .6×10-23 |
| Delta | Δ+ | uud | 1232 | +1 | 0 | 0 | .6×10-23 |
| Delta | Δ0 | udd | 1232 | +1 | 0 | 0 | .6×10-23 |
| Delta | Δ- | ddd | 1232 | +1 | 0 | 0 | .6×10-23 |
| Lambda | Λ0 | uds | 1115.7 | +1 | -1 | 0 | 2.60×10-10 |
| Lambda | Λ+c | udc | 2285 | +1 | 0 | 1 | 2.0×10-13 |
| Sigma | Σ+ | uus | 1189.4 | +1 | -1 | 0 | 0.8×10-10 |
| Sigma | Σ0 | uds | 1192.5 | +1 | -1 | 0 | 6×10-20 |
| Sigma | Σ- | dds | 1197.4 | +1 | -1 | 0 | 1.5×10-10 |
| Xi | Ξ0 | uss | 1315 | +1 | -2 | 0 | 2.9×10-10 |
| Xi | Ξ- | dss | 1321 | +1 | -2 | 0 | 1.6×10-10 |
| Omega | Ω- | sss | 1672 | +1 | -3 | 0 | 0.82×10-10 |
1at least 1030
It looks fine to me, except that some numbers aren't being written in proper scientific notation. Instead of 0.6×10-23, for example, it should be 6x10-24. I would edit it myself, but I haven't quite had the time to thoroughly look through the editing system.
- The numbers are written that way so you can more easily compare the decay times of related particles. Tho in the case you cited (the Deltas), none of the related particles seem to have made the table, so there's no reason that one should be in a funny format. -- Xerxes 14:52, 2005 Mar 10 (UTC)
After reading your post, I edited the scientific notation of the Deltas.
Are you sure that the neutron has a half-life of nine hundred and twenty seconds? That seems awfully short. Didn't someone have to build a really, really big detector to try to determine the half-life, because it was extremely long? [...] Okay, I looked it up, and neutrons do decay that quickly, but only when not bound inside nuclei. Should this be mentioned? I was led to the impression that we should all be big masses of Hydrogen-1 by now. grendel|khan 23:23, 2005 Mar 11 (UTC)