Asda9001
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Re-posted below with correct scripts
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Asda9001
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I'm having some trouble identifying weak/strong interactions. When I see the exchange particle on a Feynman diagram it's very easy to see what type of interaction it is. However when I'm given something like:
P + e+ --> e- + ∑0 + K+

I struggle to see what interaction it is. I see that the interaction is a collision between a proton and positron, which would have been an electromagnetic interaction if they didn't collide. It's between a proton and positron so I'm thinking it's a weak nuclear interaction as it's not between 2 hadrons? However I can see the product was 2 strange particles which conserved the strangeness which is common in strong interactions...

What's the best way to go about this?
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Asda9001
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Callicious
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In a strong interaction, you don't have any leptons being exchanged, i.e. the only exchange particle will be your gluons, which aren't typically represented in the exchange equation(s) that are usually afforded.

Another thing worth noting is that strangeness is always conserved in strong interactions, but not always in weak. (to my awareness); you have some other niche scenarios that occur, but I can't think of any more obvious ones from the top of my head.

For this example, I can't really help. I'm struggling to entirely see how it's possible, I mean, charge isn't conserved, which to my awareness is a must for all exchanges. P + e+ -> a charge of +2... e- + K+ gives a charge of 0, hence the Sigma(0) would need a charge of +2 to balance this out. Either ways, I'm not sure this exchange would be possible.

To see that this is a weak, try drawing the exchange diagram. Charge has to be shuffled around, and you have an electron being produced. The strong force doesn't mediate those. Hence it has to be an electroweak interaction. Electromagnetic interactions, to my awareness, just apply repulsive and attractive forces, not change in particle aspects such as strangeness/etc.
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Asda9001
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(Original post by Callicious)
In a strong interaction, you don't have any leptons being exchanged, i.e. the only exchange particle will be your gluons, which aren't typically represented in the exchange equation(s) that are usually afforded.

Another thing worth noting is that strangeness is always conserved in strong interactions, but not always in weak. (to my awareness); you have some other niche scenarios that occur, but I can't think of any more obvious ones from the top of my head.

For this example, I can't really help. I'm struggling to entirely see how it's possible, I mean, charge isn't conserved, which to my awareness is a must for all exchanges. P + e+ -> a charge of +2... e- + K+ gives a charge of 0, hence the Sigma(0) would need a charge of +2 to balance this out. Either ways, I'm not sure this exchange would be possible.

To see that this is a weak, try drawing the exchange diagram. Charge has to be shuffled around, and you have an electron being produced. The strong force doesn't mediate those. Hence it has to be an electroweak interaction. Electromagnetic interactions, to my awareness, just apply repulsive and attractive forces, not change in particle aspects such as strangeness/etc.
Yeah.... Sorry for using that example. I was doing some questions on conservation of quantum numbers / charge / energy, the charge and lepton number aren't conserved in that interaction so it can't occur. But you helped me with my confusion, I guess you could put it as the strong interaction is between 2 hadrons and the weak is between 2 leptons or a hadron and lepton?

Very helpful, thanks!
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Callicious
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(Original post by Asda9001)
Yeah.... Sorry for using that example. I was doing some questions on conservation of quantum numbers / charge / energy, the charge and lepton number aren't conserved in that interaction so it can't occur. But you helped me with my confusion, I guess you could put it as the strong interaction is between 2 hadrons and the weak is between 2 leptons or a hadron and lepton?

Very helpful, thanks!
The weak can happen between quarks-only, too, it just means that charge is exchanged through the W/Z bosons, at least to my knowledge...
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