B What particle represents the mass-energy conversion in a proton?

[veemon293]

TL;DR Summary

1% of a proton's mass is quarks. 99% is mass thats been converted from energy. whats the 99% thought to be exactly? Identityless? Is it gluons or what?

i just watched this:



and now im wondering, jsut as when the atom bomb converts mass into energy and we can measure it in force and heat and electromagnetic radiation of various wavelengths, obviously just grams, but of what? what particle would we say is representing the 99% of a proton's mass that energy makes up? interquark vacuum volume-grams? i just made that last term up idk. is it liek a fraction of a quark?
thanks

 

[PeterDonis]

I just watched this

Pop science videos are not good sources to learn actual science.

the atom bomb converts mass into energy

Not really, althought that's a common pop science misstatement.

what particle would we say is representing the 99% of a proton's mass that energy makes up?

"Particle" is not a good model of what's going on inside a proton; things like quarks and gluons are quantum fields, and inside a proton the quantum field states they are in don't really have very good particle interpretations. The usual heuristic description is that a proton consists of three quarks in a complicated bound state of the strong interaction, in which, again heuristically, there are lots of virtual quarks and gluons. The mass of the proton is mostly (99% is a reasonable figure) made up of the energy contained in that bound state of the strong interaction.

 

[veemon293]

thank you very much for taking the time to read and respond to my noob question. are you saying that particles as a group are simply classifications or idealizations of quantum spaces, and that what im asking is misrevolved around such? may you please point me in the right direction of a better explanation of whats actually happening so that i could even ask a meaningful question? again, thank you.

 

[PeterDonis]

are you saying that particles as a group are simply classifications or idealizations of quantum spaces

I'm not sure what this means, but it doesn't look like a good description of what "particles" are in QFT.

At a very basic level, the term "particles" in QFT refers to states that go into or come out of scattering experiments--for example, the kind of experiments that are run at places like the LHC. So a proton itself is a particle, since we can run scattering experiments where protons go in or where protons come out. But quarks can't be treated as particles in this simple way because we can never observe them going into or coming out of scattering experiments; we can run scattering experiments with other stuff going in or coming out, that show indirect evidence of things inside protons and neutrons that we can refer to as "quarks" (for example, the "deep inelastic scattering" experiments that were run in the late 1960s and early 1970s, where electrons were fired at protons), but we can never observe the quarks directly as particles the way we observe protons or electrons directly as particles.

The other issue involved here, again at a very basic level, is that the strong interaction doesn't work like an ordinary "force" that you're used to, for example the electromagnetic interaction. With an ordinary "force" like the electromagnetic interaction, the force gets smaller as the objects get further apart (with the electromagnetic interaction this goes like the inverse square of the distance). That means that when two interacting objects get far enough apart, you can treat them as separate objects; the interaction between them is just a small correction to their behavior as separate objects.

But with the strong interaction, heuristically, the "force" gets larger as the objects get further apart. So, very heuristically, if you were to try to pull out one of the quarks from a proton, you would have to exert more and more force, until finally you were adding enough energy to make a quark-antiquark pair, and instead of pulling a free quark by itself out of the proton, you would pull a meson out (for example a pi meson, or pion). So you can never get to a point where you can treat an individual quark as a separate object where its interaction with other things is a small correction. More generally, what holds a proton together is the fact that all of its quarks have to stay very close to one another because that is what minimizes the force between them, so they can't be treated as individual particles; you have to work with the whole complicated quantum field configuration, which doesn't look anything like what goes into or comes out of scattering experiments as "particles".

The above is all oversimplification, but it is enough to show that your ordinary intuitions about particles and interactions don't work for understanding what's going on inside objects like the proton that are held together by the strong interaction.

 

[PeroK]

thank you very much for taking the time to read and respond to my noob question. are you saying that particles as a group are simply classifications or idealizations of quantum spaces, and that what im asking is misrevolved around such? may you please point me in the right direction of a better explanation of whats actually happening so that i could even ask a meaningful question? again, thank you.

First, energy is a property of a system. It's not in itself a thing. The equation $E=mc^2$ is really saying that a particle of mass $m$ has an inherent energy of $mc^2$, when at rest. More generally, the energy of a particle is given by:
$$E^2 = p^2c^2 + m^2c^4$$Where $p$ is the magnitude of the particle's momentum.That ought to be the most famous equation in physics!

Second, mass at the quark scale is a slippery concept. A proton is a more complicated object that just three quarks bouncing around. It becomes increasingly difficult to attribute the mass of a proton in a simplistic way.

I'm not sure there is a accessible explanation. For example, if you think of a quark as an elementary particle like an electron, then why can't you isolate a quark? The only answer I can give is that the laws of physics are deep and obscure and quarks are confined to combinations that make up larger particles.

If that's not a satisfactory explanation, then you are trying to dig deep into the highly mathematical theory of particle physics, where the laws are more mathematical than physical.