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For me it is incomprehensible that from the indisputable fact that a free electron - like a proton - carries a constant charge with it, one transfers this empirical finding to bound electrons (protons). In order to counter the contradiction between the repulsive charges of the protons in the atomic nucleus and the actual stability (in combination with neutrons), the strong interaction was introduced around 1970.

A stronger attractive force was postulated to explain how the atomic nucleus was bound despite the protons' mutual electromagnetic repulsion. This hypothesized force was called the strong force, which was believed to be a fundamental force that acted on the protons and neutrons that make up the nucleus. Source

How should we imagine the disappearance of charges in an annihilation process? As an entity without any transition time? Probably not. The charges as well as the solid matter of the two particles dissolve in a photon shower over an - albeit very short - period of time.

The same can also happen partially in a proton-electron process. The photons carry away not only partial mass but also partial charge, and the atom becomes what it really is when viewed from the outside - a largely neutral entity.

At what point of approach in annihilation process the charges of antiparticles disappear? How is relevant to the electron-proton interaction?

This question is in context with What are the differences between electron-positron annihilation and proton-electron scattering?

HolgerFiedler
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  • Your question (v1) says that the strong interaction was introduced around 1970. This is wrong. The Yukawa potential was proposed in 1935. – rob Apr 02 '22 at 05:37
  • @rob Perhaps I was not precise enough. I reed inky on Wiki “ Before the 1970s, physicists were uncertain as to how the atomic nucleus was bound together. It was known that the nucleus was composed of protons and neutrons and that protons possessed positive electric charge, while neutrons were electrically neutral. By the understanding of physics at that time, positive charges would repel one another and the positively charged protons should cause the nucleus to fly apart. However, this was never observed. New physics was needed to explain this phenomenon.” – HolgerFiedler Apr 02 '22 at 07:05
  • Other misunderstandings in this post include the discussion of antiparticle annihilation to electron-proton pairs (the antiparticle of the electron is the positron, not proton) and the statement "The photons carry away not only partial mass but also partial charge" which is wrong; photons have zero charge and can hence never "carry it away". That said, the essence of the question is solid: is pair annihilation and instantaneous process, and if not, what is the characteristic time? – Marius Ladegård Meyer Apr 02 '22 at 07:25
  • @MariusLadegårdMeyer Please not interpret was is not in the question. I‘m indeed talking about the approach of the electron/proton pair (in contrast to the electron/positron annihilation process). And, yes photon has zero charge, but the photon is the only thing that results from the annihilation process meanwhile the charges disappear. An not, the question is what we can learn from the annihilation for the electron-proton approach. I keenly await your response. – HolgerFiedler Apr 02 '22 at 08:16
  • The electron proton approach cannot lead to annihilation of charge due to the axiomatic conservation of lepton and baryon numbers. The times for electron proton interactions will be given by QED calculations, will be probability functions for the interaction, and will depended on the energy of scatterinng: high probability tfor capture into a hydrogen atom the smaller the scattering energy. – anna v Apr 02 '22 at 09:27
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    This question includes a lot of unnecessary speculative content that does not clarify the question but rather distracts from it. That content should be removed – Dale Apr 02 '22 at 12:56

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The question of "when" the charges of the particles involved in a quantum field theoretical interaction "change" or "disappear" is unanswerable - more precisely, this is not a question quantum field theory answers.

A scattering interaction (and annihilation is just a type of scattering in this context) has particles as input in the "asymptotic past", when the particles are too far away from each other to meaningfully interact and particles as output in the "asymptotic future", when the products of the interaction again have separated into well-defined particles. But there is no clearly identifiable "particles" in the middle when the scattering reaction takes place, just a messy and evolving quantum state. We can track neither experimentally nor theoretically the identity of a particle in the input and point to any specific point in time when it "disappears". QFT allows us to compute the probabilities for certain inputs to lead to certain outputs, but it is not tractable to produce some sort of "live view" of the scattering process - it's like a black box, particles go in, particles come out.

See also Bosoneando's answer and this answer of mine to a very similar question about "how" pair production works for lengthier discussion of why QFT does not produce human-readable stories that would allow you to track the particles here.

ACuriousMind
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  • You said “more precisely, this is not a question quantum field theory answers.” Isn’t it also true that experiment does not answer this question either? – Dale Apr 02 '22 at 12:57
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    @Dale Note that I say later "We can track neither experimentally nor theoretically [...]", but experiments are always interpreted through the lens of the theory we want to test. If there was a different theory (e.g. a theory of quantum gravity) that would answer this question and if we then tested that theory experimentally, would that count as "experiment" answering the question? Keep in mind that most collider experiments are indirect in the sense that we gather a lot of very technical detector data and then use our QFT-derived particle picture to interpret those. – ACuriousMind Apr 02 '22 at 13:43
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The electron proton approach cannot lead to annihilation of charge due to the axiomatic conservation of lepton and baryon numbers. The times for electron proton interactions will be given by QED calculations, will be probability functions for the interaction, and will depended on the energy of scattering: high probability for capture into a hydrogen atom the smaller the scattering energy.

In wikipedia the mean lifetime of a particular state of positronium is given:

The singlet state, with antiparallel spins (S = 0, Ms = 0) is known as para-positronium (p-Ps). It has a mean lifetime of 0.12 ns and decays preferentially into two gamma rays with energy of 511 keV each...

As with all quantum mechanical predictions which are probabilistic, the mean lifetime comes from integrating the probability distributions as shown in the link. A large number of measurements are needed to get at the mean lifetime. There can be no calculation predicting the time a single positronium will annihilate into the two gammas and the charge neutralized, only probabilities and averages of probabilities.

How well the QED calculations fit the data is still a matter of research experimentally, pursued by physicists looking for new physics.

Urb
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anna v
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