Calculating Z0 Decay Matrix Element: Finding the Error

[marlon1]

I want to calculate the matrix element of Z0 decay into a fermion, antofermion pair given the propagator, vertex element and fermi's golden rule.

But somewthing is going wrong.

First the propagator has a term 1/Mz^2 so
the MatrixElement^2 will go like 1/Mz^4.

but the vertex factor has a term Mz^2 so the matrix element will finally go
1/Mz^2

But according to the answer the matrix element must go like Mz^2 so I'm wrong a factor Mz^4

take a look here;

https://www.physicsforums.com/attachment.php?attachmentid=8956&d=1169839397"

 

[mjsd]

why do you have a propagtor when it is a tree-level decay... look at your Feymann diagram and you should see no propagtor.. unless I have misunderstood your interaction.

 

[sir-pinski]

It appears that there may be a mistake in your calculation. The propagator term 1/Mz^2 should not affect the overall scaling of the matrix element, as it cancels out in the final expression. It is important to carefully check all steps in your calculation and make sure they are correct.

Additionally, it is possible that there may be a mistake in the answer you are comparing your result to. It is always a good idea to double check the answer and make sure it is consistent with the known properties of the system.

If you are still unable to identify the error, it may be helpful to seek the assistance of a colleague or instructor who is familiar with the calculation. Sometimes having a fresh set of eyes can help identify mistakes that may have been overlooked.