Abstract
In this paper we discuss the Standard Model and new physics sensitivity of the \( {\Lambda}_b\to {\Lambda}^{\ast }(1520)\left(\to N\overline{K}\right){\mathrm{\ell}}^{+}{\mathrm{\ell}}^{-} \) decay at low-recoil, where ℓ± are massive leptons and \( N\overline{K}=\left\{{pK}^{-},n{\overline{K}}^0\right\} \). We provide a full angular distribution with a set of operators that includes the Standard Model operators and their chirality flipped counterparts, and new scalar and pseudo-scalar operators. The resulting angular distribution allows us to construct observables that we study in the Standard Model and in model-independent new physics scenarios. To reduce the hadronic effects emanating from the Λb → Λ* (1520) transition form factors, we exploit the Heavy Quark Effective theory framework valid at low Λ∗(1520) recoil, i.e., large dilepton invariant mass squared \( {q}^2\sim \mathcal{O}\left({m}_b^2\right) \). Working to the leading order in 1/mb and including \( \mathcal{O}\left({\alpha}_s\right) \) corrections, we compute the ‘improved Isgur-Wise relations’ between the form factors. The relations correlate the form factors and thereby allow the description of this decay at the low-recoil region with a smaller number of independent form factors.
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Das, D., Das, J. The \( {\Lambda}_b\to {\Lambda}^{\ast }(1520)\left(\to N\overline{K}\right){\mathrm{\ell}}^{+}{\mathrm{\ell}}^{-} \) decay at low-recoil in HQET. J. High Energ. Phys. 2020, 2 (2020). https://doi.org/10.1007/JHEP07(2020)002
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DOI: https://doi.org/10.1007/JHEP07(2020)002