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This article presents the first measurement of the ratio of branching fractions B(Λb0→Λc+μ-ν̄μ)/ B(Λb0→Λc+π-). Measurements in two control samples using the same technique B(B̄0→D+μ- ν̄μ)/B(B̄0→D+π-) and B(B̄ 0→D*(2010)+μ-ν̄μ)/ B(B̄0→D*(2010)+π-) are also reported. The analysis uses data from an integrated luminosity of approximately 172pb-1 of pp̄ collisions at s=1.96TeV, collected with the CDF II detector at the Fermilab Tevatron. The relative branching fractions are measured to be B(Λb 0→Λc+μ-ν̄μ)B(Λb 0→Λc+π-)=16.6±3.0(stat) ±1.0(syst)+2.6-3.4(PDG) ±0.3(EBR), B(B̄0→D+μ-ν̄μ) B(B̄0→D+π-)=9.9±1.0(stat) ±0.6(syst)±0.4(PDG)± 0.5(EBR), and B(B̄0→D*( 2010)+μ-ν̄μ)B(B̄0→D*( 2010)+π-)=16.5±2.3(stat) ±0.6(syst)±0.5(PDG)± 0.8(EBR). The uncertainties are from statistics (stat), internal systematics (syst), world averages of measurements published by the Particle Data Group or subsidiary measurements in this analysis (PDG), and unmeasured branching fractions estimated from theory (EBR), respectively. This article also presents measurements of the branching fractions of four new Λb 0 semileptonic decays: Λb0→Λc( 2595)+μ-ν̄μ, Λb0→Λc( 2625)+μ-ν̄μ, Λb0→Σc( 2455)0π+μ-ν̄μ, and Λb 0→Σc(2455)++π-μ-ν̄μ, relative to the branching fraction of the Λb0→Λc+μ- ν̄μ decay. Finally, the transverse-momentum distribution of Λb0 baryons produced in pp̄ collisions is measured and found to be significantly different from that of B̄0 mesons, which results in a modification in the production cross-section ratio σΛb0/σB̄0 with respect to the CDF I measurement. © 2009 The American Physical Society.

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Physical Review D - Particles, Fields, Gravitation and Cosmology