Measurement of the semileptonic branching fraction of inclusive b baryon decays to Lambda

We present the first measurement of the ratio RΛl defined as RΛl = BR(Λb → ΛlX)/BR(Λb → ΛX) where Λb denotes all weakly decaying b baryons and l represents the average of electrons and muons. Using all hadronic Z0 decay events collected with the OPAL detector near the Z0 resonance, we measure RΛl = (7.0 ± 1.2 ± 0.7)%. We also measure f(b → Λb) · BR(Λb → Λ X) = (3.93 ± 0.46 ± 0.37)%, f(b → B) · BR(B → Λ X) = (1.94 ± 0.28 ± 0.24)%, and BR(b → ΛX) = (5.87 ± 0.46 ± 0.48)%. In all cases, the uncertainties shown are statistical and systematic, respectively.

electron positron: colliding beams
electron positron: annihilation
Z0: electroproduction
Z0: hadronic decay
bottom: pair production
bottom: fragmentation
bottom baryon: semileptonic decay
bottom baryon: hadronic decay
bottom baryon: branching ratio
Lambda: hadronic decay

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