Identifying Forces in Reaction Equations

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Discussion Overview

The discussion revolves around identifying the fundamental forces (electromagnetic, strong, or weak) involved in reaction equations. Participants explore how to determine the governing force based on the characteristics of the reaction equations, including the use of selection rules and Feynman diagrams.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant asks how to determine the force behind a reaction by examining the reaction equation.
  • Another participant seeks clarification on which specific reaction equation is being referenced, suggesting the example "e\gamma\rightarrow e\gamma" and inquiring about familiarity with Feynman diagrams.
  • A participant provides an example reaction (P + P -> P + P) and questions whether there are consistent rules to follow for determining the outcome.
  • It is noted that the example reaction can occur via any of the three fundamental interactions, and while there are rules related to Feynman diagrams, understanding the details of each theory is necessary.
  • One participant suggests that selection rules can be used to determine the interaction type, indicating that if a reaction is allowed in strong interactions, it will proceed that way, unless it violates electromagnetic selection rules, in which case it would be weak. They also mention approximate reaction times for each interaction type.

Areas of Agreement / Disagreement

Participants express differing views on the clarity and applicability of rules for determining the governing force of reactions. While some suggest that selection rules provide a framework, others emphasize the complexity and necessity of understanding the underlying theories.

Contextual Notes

The discussion highlights the dependence on specific definitions and the complexity of determining interactions, as well as the approximate nature of the reaction times mentioned.

Who May Find This Useful

This discussion may be of interest to those studying particle physics, particularly in understanding the interactions governing reaction equations and the application of Feynman diagrams.

j-lee00
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How can you determine if a reaction occurs by the electromagnetic, strong or weak force by looking at the reaction equation
 
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Which equation are you referring too ?
Do you mean something like "[itex]e\gamma\rightarrow e\gamma[/itex]" ?
If so, are you familiar with Feynman diagrams ?
 


For example P + P -> P + P

This is just one example. but is there a set of rules that can be followed to come to the correct outcome each time
 


The process you wrote can occur via any of the three interactions.

There is a set of rules - humanino points you to them, in terms of what are called Feynman diagrams. However, I don't think there's a shortcut to figuring out what goes with what processes other than learning the details of each theory.
 


j-lee00 said:
How can you determine if a reaction occurs by the electromagnetic, strong or weak force by looking at the reaction equation
Generally, you would use selection rules.
If the reaction is allowed in strong interactions, it will interact that way.
If it cannot go by strong interactions, then it will go by EM interactions
UNLESS it violates an EM selection rule. Then it would be weak.
You can also judge by reaction time, tau, for decays.
For strong, tau~10^-23 sec.
For EM, tau~10^-20 sec.
For weak, tau~10^-8 sec.
These times are very approximate.
 

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