Anti Proton vs Neutron annihilation

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Discussion Overview

The discussion explores the interactions between antiprotons and neutrons, specifically focusing on the nature of annihilation, the composition of quarks, and the resulting particles from such collisions. It includes theoretical considerations and implications of quantum chromodynamics (QCD).

Discussion Character

  • Technical explanation
  • Debate/contested
  • Exploratory

Main Points Raised

  • Some participants confirm that an antiproton consists of 2 anti up quarks and 1 anti down quark, but note the presence of a "sea of virtual quarks" and gluons.
  • There is contention regarding whether an antiproton can annihilate with a neutron, with some stating that such annihilation does not result in photons but can lead to hadronization, producing pions instead.
  • Participants discuss the annihilation of an anti up quark with a normal up quark, agreeing that this can result in specific outcomes like the production of photons.
  • One participant seeks clarification on the claim that a proton would not be annihilated by an antiproton, prompting further elaboration on hadronization and the dominance of QCD in these interactions.
  • It is suggested that low-energy collisions between protons and antiprotons typically produce pions while conserving charge, with similar outcomes expected for neutron-antiproton collisions.
  • At higher energies, the discussion indicates that collisions may lead to baryons and additional pions, but the specifics remain uncertain.

Areas of Agreement / Disagreement

Participants express differing views on the nature of annihilation between antiprotons and neutrons, with no consensus reached on whether this process can be classified as annihilation in the traditional sense. The discussion remains unresolved regarding the implications of hadronization and the outcomes of such interactions.

Contextual Notes

Participants highlight the complexity of interactions at the quark level and the influence of quantum chromodynamics, indicating that assumptions about annihilation processes may depend on energy levels and specific conditions of the collisions.

Stephanus
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Dear PF Forum,
Just out of curiosity.
What happens when an anti proton hits a 'normal' neutron?
According to this:
https://en.wikipedia.org/wiki/Proton
https://en.wikipedia.org/wiki/Neutron
A proton has 2 up quarks, 1 down quark
A neutron has 1 up quark, 2 down quarks.

1. Does anti proton has 2 anti up quarks and 1 anti down quark
2. Can antiproton be annihilated with 'normal' neutron?
3. Can anti up quark be annihilated with 'normal' up quark?
4. So if anti proton can be annihilated with neutron what would the result? 1 anti up quark and 1 'normal' down quark?

Thank you very much. Just out of curiosity
 
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Stephanus said:
1. Does anti proton has 2 anti up quarks and 1 anti down quark
yes. But these are called valance quarks. There is also a "sea of virtual quarks" and the gluons.

Stephanus said:
2. Can antiproton be annihilated with 'normal' neutron?
annihilation in the sense of "disappearing" and giving photons, no. The proton would not be annihilated with an antiproton either. They can lead to hadronization however; eg pions.

Stephanus said:
3. Can anti up quark be annihilated with 'normal' up quark?
yes. For example the \pi^0 \rightarrow \gamma \gamma is such an annihilation.

Stephanus said:
4. So if anti proton can be annihilated with neutron what would the result? 1 anti up quark and 1 'normal' down quark?
there can be many ways for them to interact (especially with their gluons)
 
Thanks ChrisVer for the answer
ChrisVer said:
Stephanus said:
2. Can antiproton be annihilated with 'normal' neutron?
annihilation in the sense of "disappearing" and giving photons, no. The proton would not be annihilated with an antiproton either. They can lead to hadronization however; eg pions.
But, please did you say the proton would not be annihilated with an antiproton either?Would you elaborate a little? Thanks.
 
Stephanus said:
But, please did you say the proton would not be annihilated with an antiproton either?Would you elaborate a little? Thanks.

Simply put they will result to hadronization... if you want, you can consider it as annihilation but it's not that they give photons, they give hadrons [because QCD dominates]
One example I found fast by google:
http://teachers.web.cern.ch/teachers/archiv/HST2002/feynman/exampl14.gif
p\bar{p} \rightarrow n \bar{n}
 
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The most likely result of a proton-antiproton collision at low energy is an annihilation-like reaction which produces a few pions and destroys proton and antiproton. As charge is conserved, the number of negative and positive pions is the same.
The most likely result of a neutron-antiproton collision at low energy is an annihilation-like reaction which produces a few pions and destroys neutron and antiproton. As charge is conserved, the number of negative pions will be 1 larger than the number of positive pions.

Very similar reactions.
At higher energy, it is more likely that the collision still leads to baryons (can be the original ones, but different ones are frequent as well) plus additional pions.
 
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