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![[parent]](https://images.physicslibrary.org/images/uparrow.png) Viewing Message
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| ``Re: Definition of "Fundamental particles"''
by hobo_physicist on 2007-05-23 03:02:57 |
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| Quarks have not been observed in isolation, because when you try to remove a quark from a bound state say in a proton (an example of a baryon), a new quark and anti-quark pair is formed from the energy that you put into it to remove the orginal quark. The new antiquark then forms a new bound state with the orginal quark which gives you a meson which is another composite particle. If I remember correctly, with sufficient energy, baryons can also be formed, but the main point is that new particles will always be created that will bind themselves to the isolated quarks before you get a chance to see them by themselves.
There's also the restriction of color neutrality. The strong force has three kinds of charges (as opposed to electromagnetism, which only has positive and negative). That's why the theory of the strong force, the 'force' that keeps nuclei stable and is the source of nuclear power, is called QCD(Quantum Chromodynamics). The C in the QCD is the reference to color charge. Color because the colors are red, blue and green (RBG). But you never observe a pure color particle on its own, which is the equivalent of seeing a particle with pure electric charge (plus or minus). They're always color charge neutral. An isolated quark will be a violation of this principle. But we know that there must be color to account for the only observed stable hardons which are baryons (qqq_bar)and mesons (qq_bar), while still obeying the Pauli Exclusion principle. It's all pretty deep and mysterious stuff which is included in the Standard Model only to account for and predict experimental data regarding strong and weak interactions. But the "why" is still not very well understood.
Anyway, in experimental high energy physics, most subatomic particles especially the fundamental ones are never observed in total isolation and are detected by their decay products and/or by their interactions with other fundamental particles inside a color neutral mess of quarks (eg in a quark gluon plasma) which only lasts for a very very short time before decaying into more familiar particles which are measurable by easy electromagnetic interactions. Which is why CERN needs the GRID to process the data from the LHC. Lots of particles will be created, which decay and then deacy somemore, until it's a huge mess and there are millions of particle tracks observed and each needs to be indentified and pieced backwards to see what had happened. And that's for only one collision, they have to do lots of collisions because of Quantum Mechanics and the whole thing about measurements never always being the same if the "wavefunction" can collapse in more than one way.
Basically, it's messy, but do a degree in physics if you want to know more :D I highly encourage it. |
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