Why Do Gluons Decay into u-anti-u Pairs Instead of Z0 Bosons?

[Onjii]

Hey!

I'm studying some particle physics. I ran into this example of a gluon decaying into a u - anti-u pair. (According to example 9: http://teachers.web.cern.ch/teachers/archiv/HST2002/feynman/examples.htm) How come this happens via strong force. Why isn't a Z0 boson doing this instead?

Thanks!

 

[Onjii]

sorry it's a d and anti-d pair!

 

[ChrisVer]

the Z0 boson could do that, but ... weak force is called 'weak' for a reason... the Z0 would be way too off-shell.
It's much more likely that a gluon will do the job... and in most of cases, if you can draw a diagram with a gluon, you'll preferably draw it with that... except for if you are interested to less probable stuff...

 

[Onjii]

Thanks, just the kind of answer i was looking for!