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

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SUMMARY

The W+ boson decays primarily into up + anti-down and charm + anti-strange quark pairs due to conservation laws governing electric charge and baryon number. The decay into up + anti-strange is not permitted as it would imply an isospin of 1/2, which contradicts the W+ boson's isospin of 1. The decay rates for W+ to up + anti-down and charm + anti-strange are significantly higher, with rates of approximately 32% and 1.7% respectively, influenced by the CKM matrix. This discussion clarifies the constraints imposed by isospin conservation in weak interactions.

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malawi_glenn
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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?
 
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I thought W^+ does -->u+sbar.
 
Meir Achuz said:
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 =)
 
Meir Achuz said:
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.
 
Last edited:
But those isospinn is not conserved in weak interaction, right?
 
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.
 
malawi_glenn said:
But those isospinn is not conserved in weak interaction, right?

Ummm... yes this is correct.
 

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