Particle Physics Struggles: Which Interactions are Most Likely?

• kylie14
In summary, the most likely interaction for the first part is EM, and the most likely interaction for the second part is via the strong force.
kylie14
I'm struggling a bit with my module on particle physics. This is only part of the problem set, but I need it for the rest (which is asking whether or not some particular decays are possible).

My problem is: How can you tell which is the most likely interaction for certain processes?

For example,

a positron and electron annihilating and producing a quark anti-quark pair;
the quark pair then goes on to hadronize.

I'm not really sure which are the most likely processes responsible but my guess is:

weak for the first part,
strong for the second part.

Is is possible that the second part is also weak?

Also, am I right in saying that processes that go via the strong force have to conserve strangeness, but ones that go via weak do not have to?

Any help would be much appreciated,
Thankyou!

Generally the "strongest" interaction that can be responsible for a particular process will be the dominant mode by which it proceeds. So any process that can occur by gluon exchange (the strong force) will usually go that way. Otherwise, it will proceed by photon exchange (EM force) if it can, and if not then by a W boson (weak force).

For your particular situation, what intermediate particle is involved when the positron and electron annihilate? That tells you what kind of process it is.

And you are correct in saying that strong interactions conserve strangeness but weak interactions don't have to. This is because weak interactions are the only ones that can change the flavor of a quark, just like strong interactions are the only ones that can change the color of a quark.

Thankyou very much, that helps me a quite a lot.

I'm not told the intermediate particle unfortunately, the question just asks which is the most likely.

Going from your reasoning that means the most likely in interaction for the first part would therefore be EM? And the second part is most likely via the strong interaction?

So then if that's the case I'd have to check for conservation of strangeness for when the quark pair hadronizes. Thankyou for also clearing up that part for me too by the way.

kylie14 said:
Thankyou very much, that helps me a quite a lot.

I'm not told the intermediate particle unfortunately, the question just asks which is the most likely.
The "meat" of the task of analyzing a particle reaction is to figure out what the intermediate particle(s) is/are. I didn't want to just give it away, but you should be able to figure it out. Usually the easiest way is to draw Feynman diagrams representing the possible interactions.
kylie14 said:
Going from your reasoning that means the most likely in interaction for the first part would therefore be EM? And the second part is most likely via the strong interaction?
Sounds reasonable.

Oh, I see! Thankyou, I'll try to draw it and see what I get.

Brilliant, thanks, I'm sorted! I think I have enough now to be able to figure it out in general.

1. What are the fundamental interactions in particle physics?

The fundamental interactions in particle physics are the strong nuclear force, weak nuclear force, electromagnetic force, and gravitational force. These interactions are responsible for the behavior and interactions of subatomic particles.

2. How do scientists study particle interactions?

Scientists study particle interactions by using particle accelerators to accelerate particles to high energies and then colliding them with each other. They also use detectors to measure the particles and their interactions.

3. Which interaction is the strongest in particle physics?

The strong nuclear force is considered the strongest interaction in particle physics. It is responsible for binding quarks together to form protons and neutrons, and also holds the nucleus of an atom together.

4. Which interaction is the weakest in particle physics?

The gravitational force is considered the weakest interaction in particle physics. It is responsible for the attraction between masses, but its effects are only noticeable at large scales.

5. Are all interactions equally likely to occur in particle physics?

No, all interactions are not equally likely to occur in particle physics. The strength of each interaction determines its likelihood of occurring. For example, the strong nuclear force is much stronger than the weak nuclear force, so interactions involving the strong force are more likely to occur.

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