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Consider some particle P, and the antiparticle aP.

Is it the case that:

  1. aP is made of the "usual" elementary particles, and indeed the same elementary particles as P, but arranged (or something) in some different way?

or,

  1. aP is made of the "usual" elementary particles, but it is made of some different combination of elementary particles than P?

or,

  1. aP is in fact made of not the usual elementary particles, but, is made of anti-elementary particles?
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  • $\begingroup$ Nicely put question Joe, can't fault your logic:) If you have the time, go a bit beyond the particles, and, depending on your background, a read of general material related to quantum field theory will give you an account of where the particles (and the anti particles) "come from", that is as excitations of a field for each entity, and it might be the differences in these fields that are more fundamental than the particles. Anybody able to correct me or clarify this (for myself as well, as I am a total newbie at QFT), please feel free to do so. $\endgroup$ – user81619 Nov 7 '15 at 19:08
  • $\begingroup$ The question might be better expressed by avoiding the term 'elementary', since each new discovery makes it clearer that so-called elementary particles are no such thing. Protons and neutrons were shown not to be elementary, as long ago as 1963 when quarks were first proposed. Now, the electron is shown to be composed of three elements. Particles currently being studied, various types of quark, are likely to be composed of smaller components: they are being smashed apart, using brute force, to learn what is inside them. We need to be very careful about using the arbitrary term 'elementary'. $\endgroup$ – Ed999 Dec 29 '16 at 22:25
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Sometimes, they are the same particles and are not "arranged in some different way", for example photons are their own antiparticles, as are the hypothetical Majorana fermions.

However the most common way that this happens is that every matter-particle, for example the electron, has an antiparticle (in this case, the positron). If you wanted to talk about the antimatter hydrogen atom, then, it would consist of a positron orbiting an antiproton:

The antiproton is made up of two anti-up quarks and one anti-down quark, just as the proton is made of two ups and a down.

enter image description here

(As indeed can easily be seen on Wikipedia)

Quark binding is actually interesting due to the existence of mesons. It turns out that color charge can be balanced in two different ways that we call "baryons" and mesons (which almost instantly decay). When a particle has three quarks, we call that a baryon: and when there's one quark and an antiquark, we call that a meson.

For example, the pions are mesons made from the same quark species as protons and neutrons: there is a $\pi^+$ made of an up and an anti-down, and a a $\pi^-$ made of a down and an anti-up, and they are antiparticles of each other. There are also two $\pi^0$ mesons, one with an up and an anti-up, and the other with a down and an anti-down, which are each their own antiparticles and, as you can imagine from containing a particle and its antiparticle together, decay almost immediately (they have something like a billionth of the lifespan of the $\pi^{\pm},$ which themselves only last for tens of nanoseconds).

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  • $\begingroup$ Thanks for that - deep. "the antiproton is made up of two anti-up quarks and one anti-down quark, just as the proton is made of two ups and a down" ... I guess, that's a good example of exactly situation "3" above. I certainly did not know that mesons are one quark and it's antiquark - and indeed further once you point it out it's "obvious" those thingies would instantly self-annihilate! $\endgroup$ – Fattie Nov 7 '15 at 18:13
  • $\begingroup$ the "tick" system often seems unfair on the physics site since there are typically so many equally excellent answers. i "tick"-ed CR since CR came along first! thanks, all! $\endgroup$ – Fattie Nov 9 '15 at 13:24
  • $\begingroup$ All anti-particles must, by definition, have an extremely short lifespan, since antimatter is formed amid a universe of ordinary matter. If antimatter is expected to annihilate with matter, such a particle can scarcely by expected to last any time at all, for it will necessarily encounter particles composed of matter immediately following its formation. $\endgroup$ – Ed999 Dec 29 '16 at 22:29
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To start with this is the table of elementary particles:

elementary particles

A corresponding table exists for antiparticles for the blue and the green colored ones, which are fermions. From the rest which are bosons the neutral ones are the antiparticles of themselves, and the antiparticle of W+ is W- and vice verso.

By definition the antiparticle has the opposite in numbers quantum numbers of a particle.

These are the building blocks of matter.

The resonances, the baryons, proton neutron, and the nuclei that are built up by baryons correspondingly have their antiparticles .

(1) aP is made of the "usual" elementary particles, and indeed the same elementary particles as P, but arranged (or something) in some different way,

the antiparticles are made up by the elementary particles in the antiparticle table.

(2) aP is made of the "usual" elementary particles, but it is made of some different set of elementary particles than P,

same answer as 1),

(3) aP is in fact made of not the usual elementary particles, but, is made of anti-elementary particles.

Yes, antiparticles are as valid as particles, except we live in a universe where particles dominate, leading to the baryon asymmetry, the CP violation

In particle physics, CP violation (CP standing for charge parity) is a violation of the postulated CP-symmetry (or charge conjugation parity symmetry): the combination of C-symmetry (charge conjugation symmetry) and P-symmetry (parity symmetry). CP-symmetry states that the laws of physics should be the same if a particle is interchanged with its antiparticle (C symmetry), and when its spatial coordinates are inverted ("mirror" or P symmetry).

It is still an open research problem to explain why our universe is made mainly out of particles, without resorting to the anthropic principle

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  • $\begingroup$ Ahh! If I understand .. So in fact there are anti-quarks. (All six.) There are anti-leptons. (All six.) However the four bosons and the Higgs particle do not have anti-particles. I suppose in short, I guess I basically didn't understand if there were anti-elementary particles (anti-quarks and so on) or if there were only anti-bigger-things (antiprotons and so on). I'm sure this answer will be useful to future readers. Thanks! $\endgroup$ – Fattie Nov 8 '15 at 16:21
  • $\begingroup$ I observe there is some discussion about whether one can talk about the W+ and W- as an antiparticle pair .. example $\endgroup$ – Fattie Nov 8 '15 at 16:22

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