# I Can a particle transform into its counter anti-particle?

#### MathematicalPhysicist

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So is there a proposed theoretical mechanism for transforming a particle into its own anti-particle?

$Electron \leftrightarrow Positron$
$Proton \leftrightarrow anti-Proton$

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#### Orodruin

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What do you mean by ”transform”? Without any other particles partaking in the process? In that case no, that would violate particle number.

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And charge conservation.

#### MathematicalPhysicist

Gold Member
What do you mean by ”transform”? Without any other particles partaking in the process? In that case no, that would violate particle number.
What I had in mind is assume we have a particle and an anti-particle and we want to switch between them.
All we need is to exchange between them is the sign of charge, is it possible?

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#### DrDu

Well don't neutral particles have zero charge and thus they are their own anti-particle?
If the answer to the above question is 'correct', then that's not what I was looking for.
Take a hydrogen atom which is neutral. If you invert the charge of both the electron and proton, you get an anti-hydrogen, which is evidently not equal to a hydrogen atom, although it is also neutral.

#### Orodruin

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Well don't neutral particles have zero charge and thus they are their own anti-particle?
If the answer to the above question is 'correct', then that's not what I was looking for.
No, this is incorrect. Neutral particles are not necessarily their own anti-particles, although it is a prerequisite for that to be the case.

Take a hydrogen atom which is neutral. If you invert the charge of both the electron and proton, you get an anti-hydrogen, which is evidently not equal to a hydrogen atom, although it is also neutral.
Well, hydrogen does not oscillate into anti-hydrogen (in the standard model) so it may be more instructive to discuss the kaons from your previous post. Neutral kaons are combinations of $s\bar d$ and $d\bar s$.

#### mfb

Mentor
Well, hydrogen does not oscillate into anti-hydrogen (in the standard model) so it may be more instructive to discuss the kaons from your previous post. Neutral kaons are combinations of $s\bar d$ and $d\bar s$.
I think that was the point. Not everything neutral is its own antiparticle.
The neutron is another example. Antineutrons are different particles.

@MathematicalPhysicist: Antiparticles differ from particles by more than just the electric charge. All quantum numbers are reversed.

#### Orodruin

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I think that was the point. Not everything neutral is its own antiparticle.
The neutron is another example. Antineutrons are different particles.
I thought the point of the OP was to ask whether particles can transform into anti-particles. For that it is naturally necessary that the particle is different from the anti-particle. The point of #5 was to say that this does indeed happen for (some) neutral particles, but the example of #8 is not one of those cases, but the kaon is.

#### DrDu

Another way to look at the situation is to say that the Kaon is only a particle when weak interaction is neglected, but is no longer a particle, once weak interaction is taken into account, but rather a superposition of two resonances with different lifetime. So strictly speaking, there is no transformation of a particle into its antiparticle here either.

"Can a particle transform into its counter anti-particle?"

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