What are Oniums and How Do They Exist?

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Oniums, such as positronium, are particles formed by a particle and its antiparticle, which raises questions about their existence due to potential annihilation. Despite their inherent instability, oniums can exist momentarily, with very short lifetimes; for example, charged pions last about 26 nanoseconds, while neutral pions exist for approximately 8 x 10^-17 seconds. The common center of mass in systems like positronium may prevent immediate annihilation, allowing these particles to exist briefly. The discussion also suggests that oniums might represent a transient state before annihilation rather than stable entities. Research into their discovery and behavior is encouraged to better understand their formation and existence.
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Homework Statement


How can an onium exist? Since it is a particle with its own antiparticle, how can it even exist? Shouldn't the particle and the anti-particle annihilate each other?

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What does your research on the topic suggest? Have you found evidence of a stable onium?
 
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gneill said:
What does your research on the topic suggest? Have you found evidence of a stable onium?
I've not been able to find any evidence for stable onium. But since it's an particle withit's own anti-particle it shouldn't be able to exist at all.
When it comes to positronium, it's an elektron and a positron that circulates around a common center of mass. Is it the common center of mass that stops them from annihilating each other?
And the pi-meson (π0) becomes a superposition. But how is it able to become a superposition instead of having the (for example) down-quark and the anti-downquark annihilation each other?
 
I think you'll find that all -oniums have very short half lives. The charged pions in particular have a mean lifetime of about 26 nanoseconds, while the neutral pion's (##\pi^0##) is really short at about 8 x 10-17 seconds.

So you might think of them as particles that are assembled and then live very briefly.
 
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gneill said:
I think you'll find that all -oniums have very short half lives. The charged pions in particular have a mean lifetime of about 26 nanoseconds, while the neutral pion's (##\pi^0##) is really short at about 8 x 10-17 seconds.

So you might think of them as particles that are assembled and then live very briefly.
I understand that have very short lifetimes. But how are they able to assemble at all? Or is -onium just an expression for the state just before a particle and it's antiparticle annihilate each other?
 
Mathilda said:
I understand that have very short lifetimes. But how are they able to assemble at all? Or is -onium just an expression for the state just before a particle and it's antiparticle annihilate each other?
Well, where/how are -oniums found? Maybe do a bit of research on their discoveries?
 
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