[nuclear physics]Understanding what's type of interaction is

[valleyman]

Homework Statement

My problem is on questions like "say if the following interactions are allowed or prohibited, and explain why." where the interactions are something like

$$p + p -> K^+ + K^-$$

or

$$e^- + p -> n + \nu_e$$

The Attempt at a Solution

Now the first one is not allowed because charge and barionic number are not conserved, ok, but the second is allowed and the solution says it is weak interaction. How do I recognize what type of interaction takes place? Are there any rules like those one of the conservation?
Note: my problem isn't specifically on those particular interactions I just need to understand how to recognize, in a general way, what type of interaction is
Thanks for the help,
valleyman

 

[vela]

Homework Statement

My problem is on questions like "say if the following interactions are allowed or prohibited, and explain why." where the interactions are something like

$$p + p -> K^+ + K^-$$

or

$$e^- + p -> n + \nu_e$$

The Attempt at a Solution

Now the first one is not allowed because charge and barionic number are not conserved, ok, but the second is allowed and the solution says it is weak interaction. How do I recognize what type of interaction takes place? Are there any rules like those one of the conservation?
Note: my problem isn't specifically on those particular interactions I just need to understand how to recognize, in a general way, what type of interaction is
Thanks for the help,
valleyman

Tip: Use \rightarrow to get an arrow in LaTeX.

Here's a few rules of thumb to help identify which interaction is responsible: If there's a photon, then you know it has to be an electromagnetic interaction. Similarly, if there's a neutrino, it has to be a weak interaction. If quark flavor isn't conserved, like in kaon decay, it's a weak interaction.

 

[valleyman]

Thanks for the help those rules are very useful but there are still some things I don't understand! what if my reaction doesn't show either photons or neutrinos? And how do I check if quark flavour is conserved?
For example
$$e+e^-\rightarrow p+\overline{p}$$
this is e.m., right? But what if it is
$$e+e^-\rightarrow k^++k^-$$
Shouldn't it be e.m. anyways? How do I decide??
Thanks
valleyman

 

[vela]

You have to know what vertices are allowed for the various leptons and quarks, and generally you have to know the quark content of the various mesons and baryons. Electrons do not have color charge, so they will not interact through the strong force. So both reactions have to be either electromagnetic, where the electron and positron annihilate and create a virtual photon, or weak, where they annihilate and emit a virtual Z. At low energies, electromagnetism is going to dominate because the Z is so massive.

With only leptons in the initial state, the quark numbers will all be 0. Since the final state consists of a particle and its antiparticle, the quark numbers for each flavor will also be 0, so there's no problem with quark flavors.

 

[paranormal]

I can provide some insight into understanding the different types of interactions in nuclear physics. In order to determine what type of interaction is taking place, we must first understand the fundamental forces that govern interactions in the subatomic world.

There are four fundamental forces in nature: gravity, electromagnetism, strong nuclear force, and weak nuclear force. Each of these forces has different characteristics and governs different types of interactions.

In the case of the first interaction (p + p -> K^+ + K^-), we can see that charge and baryon number are not conserved. This means that the interaction violates the conservation laws of electromagnetism and strong nuclear force. Therefore, we can conclude that this interaction is not allowed.

On the other hand, in the second interaction (e^- + p -> n + \nu_e), we can see that charge and baryon number are conserved. This means that the interaction follows the conservation laws of both electromagnetism and strong nuclear force. However, it also involves the creation of a neutron and an electron neutrino, which suggests the involvement of the weak nuclear force.

In general, to determine the type of interaction taking place, we must consider the conservation laws of the fundamental forces. If the interaction violates the conservation laws of one or more forces, it is not allowed. If it follows the conservation laws of all forces involved, it is allowed. Additionally, the involvement of certain particles (such as the electron neutrino in the second interaction) can also indicate the presence of a specific force.

I hope this explanation helps you understand how to recognize the type of interaction taking place in nuclear physics. Remember to always consider the conservation laws and the particles involved in order to determine the fundamental force at play.