Why is the Strong Force Responsible for Pi+ + Proton -> K+ + X?

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Discussion Overview

The discussion revolves around the interaction responsible for the reaction Pi+ + proton → K+ + unknown particle X, specifically examining whether the strong force or the weak force is the appropriate explanation. The scope includes theoretical considerations of particle interactions and conservation laws in particle physics.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant asserts that the strong force is responsible due to its significantly greater strength compared to the weak force, suggesting that if both forces could facilitate the process, the strong force would dominate.
  • Another participant questions whether either the strong or weak force could be responsible since only hadrons are involved, noting that the presence of leptons would necessitate the weak force.
  • A participant references beta decay as an example where the weak force is responsible despite the absence of leptons on one side of the equation.
  • It is proposed that the strong interactions conserve more quantities, such as quark flavor, which complicates the analysis of the unknown particle X.
  • One participant mentions that strangeness conservation could be a factor, indicating that if the weak interaction were responsible, it would affect the ability to determine the strangeness of particle X.
  • Another participant points out that some weak interactions can conserve strangeness, but reiterates that the primary reason for the strong interaction being applicable is that it can occur in this scenario.

Areas of Agreement / Disagreement

Participants express differing views on the role of the strong and weak forces in this interaction, with no consensus reached on the definitive explanation. Some agree on the dominance of the strong force, while others highlight conditions under which the weak force could be considered.

Contextual Notes

The discussion includes considerations of conservation laws, such as strangeness and quark flavor, which are not fully resolved due to the unknown nature of particle X. There are also implications regarding the conditions under which each force operates, which remain open to interpretation.

zanyzoya
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Please can you help,
I have seen an exam question which asks which interaction is responsible for the following ...
Pi+ + proton >>>>> K+ + unknown particle X

The options for the answer include both the weak and the strong force. The actual answer is the strong force. What I would like to know is why the strong force is responsible rather than the weak force?
Many thanks
Zoya
 
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The strong force is significantly stronger than the weak force. Thus, if a process can occur through both, the dominant contribution will generally come from strong interactions.

In order for this to not be the case, the process must be forbidden in strong interactions.
 
Thanks for that. And am I right in thinking that either the strong or weak force could be responsible as only hadrons are involved, ie no leptons exist on either side of the equation? If there were leptons involved on either side then only the weak force could be responsible and not the strong?
 
for example in beta decay the weak force is responsible even though there are no leptons on the lhs and only on the rhs.
 
zanyzoya said:
Thanks for that. And am I right in thinking that either the strong or weak force could be responsible as only hadrons are involved, ie no leptons exist on either side of the equation? If there were leptons involved on either side then only the weak force could be responsible and not the strong?
That is one part of it, but the strong interactions also conserve many more things, such as quark flavor. There are generally several things to check. Of course, with X being an unknown particle you really cannot check quark flavor conservation.
 
Ah I see, thanks. Later on we are asked to find the strangeness of particle X. I guess strangeness wouldn't be conserved during the weak interaction and therefore you could not answer this question. Hence another reason the interaction must be due to the strong force.
 
Some weak interactions do conserve strangeness. The main reason it is a strong interaction is that it can be.
 

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