Decay of W+ Boson: Up+Anti-Down & Charm+Anti-Strange

[malawi_glenn]

Hi I was wondering why the W+ boson is decaying into following quarks:

up + anti(down)

charm + anti(strange)

bot not:

up + anti(strange) [for example]

both electric charge and baryon number is conserved.

What am I missing? Is it the Cabibbo angle?

 

[Meir Achuz]

I thought W^+ does -->u+sbar.

 

[malawi_glenn]

I thought W^+ does -->u+sbar.

not according to my book, Povh "nuclei and particles.."

and it can't be because of the cabibbo mixing.. must ask someone at my university i guess =)

 

[mormonator_rm]

I thought W^+ does -->u+sbar.

No, it does not. W+ --> u + sbar would cause the W+ to have isospin-1/2, which it clearly cannot have. It can only have isospin-1 (for u + dbar) or isospin-0 with S=1, C=1 (for c + sbar). Similarly, Z can only have isospin-0 or 1, with only quark-antiquark pairs forming in decay products.

 

[malawi_glenn]

But those isospinn is not conserved in weak interaction, right?

 

[studnte]

W could decay to us,cd. but compare to ud,cs, it's rate is small. W->us,cd rates are around 1.7%. but to ud,cs,the rates around 32%. you could find the difference in CKM.

 

[mormonator_rm]

But those isospinn is not conserved in weak interaction, right?

Ummm... yes this is correct.