Testing the W -exchange mechanism with two-body baryonic B decays

摘要

A bstract The role of W -exchange diagrams in baryonic B decays is poorly understood, and often taken as insignificant and neglected. We show that charmful two-body baryonic B → B c B ˉ ′ documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$ Bo {mathbf{B}}_coverline{mathbf{B}}^{prime } $$end{document} decays provide a good test-bed for the study of the W -exchange topology, whose contribution is found to be non-negligible; here B _( c )is an anti-triplet or a sextet charmed baryon, and B ˉ ′ documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$ overline{mathbf{B}}^{prime } $$end{document} an octet charmless (anti-)baryon. In particular, we calculate that ? B ˉ 0 → Σ c + p ˉ = 2.9 ? 0.9 + 0.8 × 10 ? 6 documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$ mathrm{mathcal{B}}left({overline{B}}^0o {Sigma}_c^{+}overline{p}ight)=left({2.9}_{-0.9}^{+0.8}ight)imes {10}^{-6} $$end{document} in good agreement with the experimental upper bound. Its cousin B ˉ s 0 documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$ {overline{B}}_s^0 $$end{document} mode, B ˉ s 0 → Λ c + p ˉ documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$ {overline{B}}_s^0o {Lambda}_c^{+}overline{p} $$end{document} , is a purely W -exchange decay, hence is naturally suited for the study of the role of the W -exchange topology. We predict ? B ˉ s 0 → Λ c + p ˉ = 0.8 ± 0.3 × 10 ? 6 documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$ mathrm{mathcal{B}}left({overline{B}}_s^0o {Lambda}_c^{+}overline{p}ight)=left(0.8pm 0.3ight)imes {10}^{-6} $$end{document} , a relatively large branching ratio to be tested with a future measurement by the LHCb collaboration. Other predictions, such as ? B ˉ 0 → Ξ c + Σ ˉ ? = 1.1 ± 0.4 × 10 ? 5 documentclass[12pt]{minimal} usepackage{amsmath} usepackage{wasysym} usepackage{amsfonts} usepackage{amssymb} usepackage{amsbsy} usepackage{mathrsfs} usepackage{upgreek} setlength{oddsidemargin}{-69pt} egin{document}$$ mathrm{mathcal{B}}left({overline{B}}^0o {Xi}_c^{+}{overline{Sigma}}^{-}ight)=left(1.1pm 0.4ight)imes {10}^{-5} $$end{document} , can be tested with future Belle II measurements.