Wikipedia:Reference desk/Archives/Science/2021 February 11

= February 11 =

photons between quarks in protons, neutrons, and mesons- what energies?
I’ve been told, if I understand it right, that the 3 quarks in a proton interact both through the strong force and electromagnetic force, with the quarks exchanging gluons for the strong force. Should the quarks also be exchanging photons for the electromagnetic force? If so, what are their energies? Are they even higher than the energies of gamma rays from nuclear fusion or fission? Do they compare with the photon energies from particle accelerators?Rich (talk) 07:15, 11 February 2021 (UTC)
 * They will be exchanging virtual photons. Dja1979 (talk) 17:50, 11 February 2021 (UTC)
 * There's not a simple answer to all the parts of this question. The quarks in a proton do have electromagnetic interactions with each other. There's an approach called perturbation theory where interacting quantum fields are modeled by a sum of virtual particle exchanges (Feynman diagrams), but perturbation theory can't handle everything, and it doesn't mean that quantum fields are "really" deep-down built out of virtual particles. We have an article that aims at some of the same questions you ask: static forces and virtual-particle exchange. It's not easy reading and it's also not perfect. The article has a subsection "The Coulomb potential in a vacuum" under "Electrostatics" that is most relevant to your question, along with the "energy of interaction" above. Your question about photon energies translates into "what photon energies appear in the relevant integrals?" Even this is complicated by the fact that solving the integral involves mathematical tricks like assigning a mass to the photon and then taking the limit as the mass approaches zero in the very last step. This kind of trick doesn't really have or respect any notion of how many virtual photons are involved or how much energy each one might have. (And that's to be expected, because virtual particles always were a mathematical trick to start with, and not real things that have definite properties.) If I hesitantly make an attempt (which is probably unwise), and noting that the quarks in a proton are not static (as in the worked example), I think the best we can say is "all possible energies, even including negative energies, but almost all infinitesimally close to zero." --Amble (talk) 19:12, 11 February 2021 (UTC)


 * Instead of trying to consider the electromagnetic interaction as photons, you could also consider it as a field. you can work out the electric field and force induced by the quarks based on their charge and distance. The magnetic field is also significant, and you would have to know the velocity of the particles to calculate that. Graeme Bartlett (talk) 00:18, 15 February 2021 (UTC)

Journal of Geoscience Education article
For Alfred Woodford, I'm looking to get access to this article. My Taylor & Francis subscription from the Wikipedia Library doesn't seem to be sufficient, though. Does anyone have access to it? From the Google preview, it looks like it will contain a non-rounded version of the infobox photo (copyright expired), which would be great to extract. &#123;{u&#124; Sdkb  }&#125;  talk 22:03, 11 February 2021 (UTC)
 * Can you grab the image from here? --Lambiam 00:59, 12 February 2021 (UTC)
 * The Resource Exchange is probably the best place to ask. DuncanHill (talk) 08:54, 12 February 2021 (UTC)
 * Made request there; thanks for the pointer! &#123;{u&#124; Sdkb  }&#125;  talk 18:41, 12 February 2021 (UTC)