Is it possible for different particle-antiparticl pair to annihilate with each other?

  • #1

Main Question or Discussion Point

I've been searching about particle-antiparticle annihilation and I've been wondering whether it was possible for particle to annihilate with antiparticle that is not its pair? Can annihilation occur with collision of different particle-antiparticle quarks(e.g. up antiquark and strange quark), with different particle-antiparticle leptons(e.g. electron antineutrino and muon) or with particle-antiparticle quark and lepton(e.g. bottom quark and antitau)?
 

Answers and Replies

  • #2
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Usually not, as this would violate some conserved quantum numbers (charge, lepton numbers and so on). In addition, the "classic" annihilation via the electromagnetic force requires particle + corresponding antiparticle.

However, the weak interaction can allow some processes which could be considered as annihilation of different particles: Neutral kaons (strange + anti-down quark or anti-strange + down-quark) can decay to two photons, for example.
 
  • #4
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12


In some cases yes, It depends on wheter the annihilation violates conservation laws.
For example, in the quark sector flavor conservation is violated by intercation with the W boson.

Therefore, for example

[itex]u\bar{s}->W^{+}->e^{+}\nu_{e}[/itex] is possible

In the lepton sector, in the limit of massless neutrinos, flavor is conserved and a muon can't annihilate with a electron neutrino( or anti electron neutrino).

quarks and leptons can't annihilate with eachother due to baryon and lepton number conservation. ( which is simply an outcome of other conservation laws (charge, color etc..) doesn't have to be assumed)
 
  • #5


Usually not, as this would violate some conserved quantum numbers (charge, lepton numbers and so on). In addition, the "classic" annihilation via the electromagnetic force requires particle + corresponding antiparticle.

However, the weak interaction can allow some processes which could be considered as annihilation of different particles: Neutral kaons (strange + anti-down quark or anti-strange + down-quark) can decay to two photons, for example.
So, do you mean, without weak interaction, such annihilation is impossible?
 
  • #6
34,457
10,571


Some reactions "particle + different antiparticle -> 2 photons" are possible, but they have to include the weak interaction (together with the electromagnetic interaction).

One up-type quark (up, charm, top) plus a different up-type antiquark can annihilate to 2 photons.
One down-type quark (down, strange, bottom) plus a different down-type antiquark can annihilate to 2 photons.

Hmm.. I think if we neglect neutrino mixing, that was all.
 

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