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Oheligud OP t1_jbytqwq wrote

Reply to comment by ChromaticDragon in As they still have a neutral charge, can antineutrons replace neutrons in a regular atom? by Oheligud

I thought antiparticles only annihilated with their respective particles? Could you not have a Hydrogen atom with one proton, one antineutron, and one electron?

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Ridley_Himself t1_jbyvn95 wrote

The issue here is that protons, neutrons, and their respective antiparticles are not elementary particles; they are made of quarks and antiquarks respectively bound together by gluons. A proton contains two up quarks and one down quark. An antineutron contains two down antiquarks and one up antiquark. A quark from the proton and an antiquark from the antineutron would annihilate and produce mesons from the remaining (anti)quarks, which would quickly decay.

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LeN3rd t1_jbzaooe wrote

Wouldn't that leave Single Quarks? I thought that was a nono

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Narwhal_Assassin t1_jbzcasy wrote

You’d have an up quark-antiquark annihilation, and a down quark-antiquark annihilation, leaving behind an up quark and a down antiquark. These have charges of +2/3 e and +1/3 e, respectively, so they can combine to form a meson with a +1 charge (I forget what the specific name would be, probably a pi meson?). So, the proton-antineutron annihilation is totally fine in terms of charge conservation and in terms of not leaving solo quarks.

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migueltrout t1_jbztpck wrote

It absolutely boggles my mind that we as human beings have discovered this knowledge.

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Emu1981 t1_jc0imbi wrote

>It absolutely boggles my mind that we as human beings have discovered this knowledge.

What is even more mind boggling is that we could be completely wrong about it all and not even know it - the old story about the blind men describing a elephant by touch comes to mind. We cannot "see" quarks but rather we can only see how they effect the physical world (e.g. via destroying matter in a particle accelerator).
We then infer what they are and build models to describe what we see. All it would take is a discovery that changes our understanding of one little part to completely upend the model.

*edit* bleh, no idea why Reddit insists that there should be a line break in there.

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ontopofyourmom t1_jc0ky76 wrote

We could be, but this is part of the most accurate and best-proven scientific theory in existence.

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ApeMummy t1_jc0hsqq wrote

Question: how do sets of quarks annihilate simultaneously? Why doesn’t the energy released from the first annihilation cause the other quarks to scatter? Do they occupy the same physical space meaning all the annihilations are simultaneous?

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ghedipunk t1_jc11cgc wrote

The models presented so far don't describe individual quarks.

Rather, nuclear particles (the protons, antiprotons, neutrons, and antineutrons) are a soup of quarks and gluons that, on average, add up to a specific number of quarks.

So, yeah... for a basic understanding, watch this: https://www.youtube.com/watch?v=WZfmG_h5Oyg

To answer your question: We're firmly outside of the ideas we're familiar with when we think of particles. There is no concept of simultaneity at this scale; you need to rely on probabilities only.

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Sable-Keech t1_jc07hox wrote

Wouldn’t the proton and the antineutron remain far enough away to avoid their component antiquarks from annihilating?

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Hotdropper t1_jc0rs2a wrote

Quantum chromodynamics is the answer here, I believe.

Essentially, the proton and neutron in a hydrogen atom (or any atom) aren’t static.

They are constantly swapping roles back and forth, the proton losing some energy and turning into a neutron, and the neutron then picking up that shed energy and turning into a proton.

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Quantum_Patricide t1_jc4rwsb wrote

If you look at the quantum energy levels, the proton and the antineutron, being distinct fermions, can occupy the same energy level (in this case the 1s orbital) and so would be literally in the same place as opposed to far away.

Secondly, the nuclear interaction inside nuclei essentially consists of nucleons swapping quarks with eachother (and creating virtual antiquarks so overall a meson is the exchange particle). So if the proton and the antineutron were bound then an up quark would move from the proton to the antineutron but interact with the antiup quark there and annihilate.

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ChromaticDragon t1_jbz47a9 wrote

To give you some meat to chew on regarding the descriptions others have already provided you, check out this paper, specifically section 5.5:

>Annihilation on neutrons
>Antiproton–neutron or antineutron–proton interactions at rest offer additional opportunities to study annihilation dynamics.

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Bag-Weary t1_jbyuv63 wrote

A neutron is made of up, down, down quarks, and a proton is made of up, up, down. An antineutron would be antiup, antidown, antidown, and the ups and antiups and the downs and antidowns would annihilate if it was in the same atom as a proton.

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mfb- t1_jbzmvab wrote

> I thought antiparticles only annihilated with their respective particles?

Reacting with the respective partner is easier (in the sense that it's always possible), but annihilation is not limited to that. Protons and antineutrons will react in almost the same way as protons and antiprotons or neutrons and antineutrons, producing a couple of pions as most likely result.

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