Suppression of semileptonic lambda decays

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SUMMARY

The discussion centers on the suppression of semileptonic lambda decays, specifically comparing the branching ratios of the decay processes uds → proton + e- + neutrino and uds → proton + pion. The leptonic decay is observed to be significantly suppressed, with a branching ratio on the order of 10^-4. The participants highlight the role of W boson production during the flavor change of the strange quark and suggest that momentum distribution among particles of similar mass contributes to this suppression. The concept of helicity suppression is also mentioned as a potential factor influencing the decay rates.

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Fek
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Confused by the branching ratio of uds ---> proton + e- + neutrino compared to uds ---> proton + pion (or neutron + pion).

In both cases an W boson is being produced as the strange quark changes flavour, and it is either decaying to leptons or first generation quarks - why is the leptonic decay so suppressed? (BR of order 10^-4).

I can see it must be easier to distribute momentum to two particles of similar mass, but is there a simple way to quantify this without doing the full phase space calculation?
 
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Helicity suppression?
 

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