A bstract We study the differential decay rate for the rare Λ~( b )→ Λ(→ N π) ? _(+) ? _(?)transition, including a determination of the complete angular distribution, assuming unpolarized Λ~( b )baryons. On the basis of a properly chosen parametrization of the various helicity amplitudes, we provide expressions for the angular observables within the Standard Model and a subset of new physics models with chirality-flipped operators. Hadronic effects at low recoil are estimated by combining information from lattice QCD with (improved) form-factor relations in Heavy Quark Effective Theory. Our estimates for large hadronic recoil — at this stage — are still rather uncertain because the baryonic input functions are not so well known, and non-factorizable spectator effects have not been worked out systematically so far. Still, our phenomenological analysis of decay asymmetries and angular observables for Λ~( b )→ Λ(→ Nπ ) ? _(+) ? _(?)reveals that this decay mode can provide new and complementary constraints on the Wilson coefficients in radiative and semileptonic b → s transitions compared to the corresponding mesonic modes.
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机译：Bstract我们研究了稀有λ〜（b）→λ（→nπ）的差分衰减率？ _（+）？ _（？）转换，包括确定完整的角度分布，假设非偏振λ〜（b）baryons。 On the basis of a properly chosen parametrization of the various helicity amplitudes, we provide expressions for the angular observables within the Standard Model and a subset of new physics models with chirality-flipped operators.通过在重型夸克有效理论中与（改进的）形式因子关系将信息组合通过与重大夸克有效理论的形式关系相结合来估计低压反冲的辐射效应。我们对大型Hadronic反冲的估计 - 在这个阶段 - 仍然是相当不确定的，因为缩放式输入功能不是如此众所周知的，并且到目前为止，不可分解的观众效应尚未系统地解决。尽管如此，我们对λ〜（b）→λ（→nπ）的衰减不对称和角度可观察的现象学分析？ _（+）？ _（？）显示，与相应的模型模式相比，该衰减模式可以在辐射和半端子B→S转换中的威尔逊系数上提供新的和互补限制。
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