Strong, weak, electromagnetic interactions

In summary, the speaker had a list of reactions and was trying to determine if they were strong or weak interactions. They were confused about the role of leptons and photons in determining the type of interaction. The speaker also questioned the conservation of strangeness in some of the reactions. The expert suggests checking isospin and third component of isospin to determine the type of interaction, and also clarifies that not all weak interactions involve neutrinos. The expert also explains that the observed muons in the second reaction are mostly from electromagnetic interactions, and that the third reaction is weak because it involves a change in strangeness. The speaker brings up another reaction involving a Lambda minus baryon, but the expert corrects that it should be a
  • #1
genloz
76
1

Homework Statement


I had a whole list of reactions and had to show whether or not they could occur... I understood most of the reasons, bar the following, but was more confused about whether or not a reaction was strong or weak... I know that if the reaction involves a lepton its weak, and if it involves a photo, it's electromag, but baryons alone don't define whether a reaction is strong or weak:
For example:

[tex]\Sigma^{-} \rightarrow n + \pi^{-}[/tex]
I understand strangeness is not conserved, but why is it a weak interaction if it only involves hadrons?

[tex]e^{+} + e^{-} \rightarrow \mu^{+} + \mu^{-}[/tex]
Why is this an electromag reaction when only leptons are involved and charge is conserved on both sides and no photons are involved? Shouldn't it be a weak?

[tex]K^{-} \rightarrow \pi^{-} + \pi^{0}[/tex]
This only involves hadrons and strangeness isn't conserved, so should this be an impossible strong reaction?
I thought weak decays only didn't conserve partity, but the answers say this is a possible weak decay, does that mean weak decays don't need to conserve strangeness either? Also why is it weak rather than strong?

[tex]\pi^{-} + p \rightarrow \Lambda^{-} + \K^{0}[/tex]
I thought this would be prevented due to lack of strangeness conservation, but it's allowed via the strong interaction, why?

Thanks very much!
 
Physics news on Phys.org
  • #2
[tex]\Sigma^{-} \rightarrow n + \pi^{-}[/tex]

Have you checked isospin and 3-component of isospin? It can be a weak, if it is done by a W boson. The general rule you are referring to that if neutrinos are emitted, then it is weak, don't go the reverse way, it is not equivalence. All neutrinos comes from weak, but not all weak produces neutrinos. So you must give up this thinking, same holds for the EM interaction.

[tex]e^{+} + e^{-} \rightarrow \mu^{+} + \mu^{-}[/tex]
can proceed both by virtual photon and Z-boson, i.e it can do both weak and EM, but weak is ... weak = unlikley, so the observed muons comes from EM interaction in like 99.99999999999999999999999999999999999% of the cases.

[tex]K^{-} \rightarrow \pi^{-} + \pi^{0}[/tex]
Strangeness is not conserved right? So it is a weak.
Also: Check isopspin and 3-component of isospin.


[tex]\pi^{-} + p \rightarrow \Lambda^{-} + K^{0}[/tex]

I have never heard of Lambda minus baryon.. you must mean lamda zero (charge is not concerved otherwise)
Lamda-0 has one strange quark, and K-0 has one anti-strange quark, so total strangeness is conserved.
Please check if you wrote this reaction correct before proceeding altough.
 
Last edited:
  • #3
pi- I:1 I3:1 Tz: ??
pi0 I:1 I3:0 Tz: ??
n I:1/2 I3:1/2 Tz:uud 1/2-1/2-1/2:-1/2
K- ubar s I: 1/2+0:1/2 I3:-1/2+0: -1/2 Tz: ??
Sigma- dds I:1/2+1/2+0:1 I3:-1/2+-1/2+0:-1 Tz: -1/2-1/2-1/2
Tz: u c t neutrinos 1/2
Tz: d s b charged leptons -1/2So
[tex]\Sigma^{-} \rightarrow n + \pi^{0}{/tex]
I: 1 -> 1/2 + 1 not conserved
I3: -1 -> 1/2 + 0 not conserved
Tz: not sure

[tex]K^{-} \rightarrow \pi^{-} + \pi^{0}{/tex]
I: 1/2 -> 1 + 1 not conserved
I3: -1/2 -> 1 + 0 not conserved
Tz: not sure

Whcih still doesn't make sense...
 
  • #4
You don't know what isospin and third component of isospin is? Look it up. i can't help you with that.

I don't understand what you have written... just a mess, neutrinos don't have isospin etc..

Aslo check the thing i wrote to you regarding last reaction with that lamda minus of yours.
 

What are the strong, weak, and electromagnetic interactions?

The strong, weak, and electromagnetic interactions are three of the four fundamental forces of nature. They are responsible for the interactions between subatomic particles and play a crucial role in the structure and behavior of matter.

What is the difference between the strong, weak, and electromagnetic interactions?

The strong interaction is responsible for the binding of quarks and gluons within protons and neutrons. The weak interaction is responsible for radioactive decay and the transformation of particles. The electromagnetic interaction is responsible for the interactions between charged particles and is responsible for many everyday phenomena such as electricity, magnetism, and light.

How do the strong, weak, and electromagnetic interactions work together?

The strong, weak, and electromagnetic interactions work together to govern the behavior of particles at the subatomic level. They can interact with each other and cause particles to change or transform into other particles. The combination of these interactions allows for the diversity and complexity of matter in the universe.

What is the role of the strong, weak, and electromagnetic interactions in the Standard Model of particle physics?

The Standard Model of particle physics is a theory that describes the fundamental particles and their interactions. The strong, weak, and electromagnetic interactions are all included in this model, along with the fourth fundamental force, gravity. The Standard Model has been extremely successful in predicting and explaining the behavior and interactions of subatomic particles.

Can the strong, weak, and electromagnetic interactions be unified into one theory?

Scientists have been working on theories that attempt to unify the strong, weak, and electromagnetic interactions into one unified theory. This is known as the theory of everything or the grand unified theory. While there have been significant advancements, a complete and proven theory has yet to be achieved.

Similar threads

  • Advanced Physics Homework Help
Replies
1
Views
1K
  • Advanced Physics Homework Help
Replies
2
Views
1K
  • Advanced Physics Homework Help
Replies
1
Views
1K
  • High Energy, Nuclear, Particle Physics
Replies
4
Views
1K
  • Advanced Physics Homework Help
Replies
4
Views
2K
  • Advanced Physics Homework Help
Replies
13
Views
7K
  • Advanced Physics Homework Help
Replies
5
Views
3K
  • Advanced Physics Homework Help
Replies
3
Views
5K
  • Advanced Physics Homework Help
Replies
14
Views
7K
  • Advanced Physics Homework Help
Replies
13
Views
3K
Back
Top