On empirical evidence for compositeness

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In summary, the conversation is discussing the idea that it is difficult to distinguish between elementary and composite particles in experiments. This is because even if indirect tests suggest sub-structure, it is still possible for particles to have properties that make them appear to be elementary. However, experiments at the LHC are searching for evidence of compositeness.
  • #1
metroplex021
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Hi folks,

I just read a passage by the great Ashoke Sen in which he writes that, due to the possibility of particle production in collisions, "strictly speaking there is no experiment possible even in principle that can distinguish elementary from composite particles."

But how is this right? Is it not the case that the structure functions obtained from deep inelastic collisions showed unambiguously that protons were composite? Perhaps there is something buried in the 'strictly speaking' here, but if anyone has any thoughts to contribute on the matter I'd be most happy to hear them!
 
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  • #2
What Sen seems to mean is that if electrons fly out of the nucleus in beta decay, this does not mean there are electrons in the nucleus. You are right, that indirect tests can indicate sub-strucutre.
 
  • #3
You can show that particles are composite particles.
The other direction is a bit tricky - it could always be a deeply bound state of two very heavy particles where (due to some weird coincidence) all particle properties agree with those you would expect from an elementary particle. Those models are the reason why LHC experiments look for compositeness.
 

FAQ: On empirical evidence for compositeness

1. What is compositeness?

Compositeness refers to the idea that a particle, such as an electron or a quark, may actually be made up of smaller, more fundamental particles.

2. What is empirical evidence?

Empirical evidence is evidence that is based on observation and experimentation. It is used to support or refute a hypothesis or theory.

3. How is compositeness tested using empirical evidence?

Compositeness can be tested using various methods, including high-energy particle collisions, measurement of particle properties, and analysis of decay products. These experiments aim to observe any substructures or interactions within the particle, which would indicate compositeness.

4. What are some examples of particles that have been found to be composite?

Some examples of particles that have been found to be composite include protons, neutrons, and other hadrons. These particles are made up of quarks and gluons, which are the more fundamental building blocks of matter.

5. What implications does the existence of compositeness have on our understanding of the universe?

The existence of compositeness has significant implications on our understanding of the universe, as it suggests that the fundamental building blocks of matter may be more complex than previously thought. It also raises questions about the nature of forces and interactions between particles, and may lead to new discoveries and theories in physics.

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