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arXiv · hep-ph/0112145

Λ_b \to ΛJ/ψdecay in perturbative QCD

Chung-Hsien Chou·Hsien-Hung Shih·Shih-Chang Lee·Hsiang-nan Li
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Abstract

We calculate the amplitudes involved in the heavy baryon nonleptonic decay $Λ_b \rar ΛJ/ψ$ using perturbative QCD factorization theorem, which are expressed as convolutions of hard $b$ quark decay amplitudes with the $Λ_b$ baryon, $Λ$ baryon and $J/ψ$ meson distribution amplitudes. It is found that nonfactorizable contributions dominate over factorizable ones. Because of soft cancellation in pairs of nonfactorizable diagrams, the $Λ_b \rar ΛJ/ψ$ decay is characterized by a large scale, such that perturbative QCD is applicable. Employing the distribution amplitudes determined in our previous works and from QCD sum rules, we derive the branching ratio $B(Λ_b \rar ΛJ/ψ)=(1.7 \sim 5.3)\times 10^{-4}$ in agreement with data. We predict an asymmetry parameter $α= -0.17 \sim -0.14$ associated with the anisotropic angular distribution of the $Λ$ baryons produced in polarized $Λ_b$ baryon decays.

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Chung-Hsien Chou, Hsien-Hung Shih, Shih-Chang Lee, Hsiang-nan Li. 2001-12-11. Λ_b \to ΛJ/ψdecay in perturbative QCD. https://doi.org/10.1103/physrevd.65.074030

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