The ${\Lambda }_b\to {\Lambda }^{\ast }(1520)(\to N\bar{K}){\ell }^{+}{\ell }^{-}$ decay at low-recoil in HQET

Abstract

In this paper we discuss the Standard Model and new physics sensitivity of the ${\Lambda }_b\to {\Lambda }^{\ast }(1520)(\to N\bar{K}){\ell }^{+}{\ell }^{-}$ decay at low-recoil, where ${\ell }^{\pm }$ are massive leptons and $N\bar{K}=\{p{K}^{-},n{\bar{K}}^0\}$. 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 ${\Lambda }_b\to {\Lambda }^{\ast }(1520)$ transition form factors, we exploit the Heavy Quark Effective theory framework valid at low ${\Lambda }^{\ast }(1520)$ recoil, \emph{i.e.,} large dilepton invariant mass squared $q^2\sim \mathcal{O}(m_b^2)$. Working to the leading order in $1/m_b$ and including $\mathcal{O}({\alpha }_s)$ 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.

30 pages, 4 figures, 1 table, the version to appear in JHEP

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Cited by in corpus (9)

• ${\Lambda }_c\to {\Lambda }^{\ast }(1520)$ form factors from lattice QCD and improved analysis of the ${\Lambda }_b\to {\Lambda }^{\ast }(1520)$ and ${\Lambda }_b\to {\Lambda }_c^{\ast }(2595,2625)$ form factors
• ${\Lambda }_b\to {\Lambda }^{\ast }(1520){\ell }^{+}{\ell }^{-}$ form factors from lattice QCD
• The time-dependent angular analysis of $B_d\to K_S\ell \ell$, a new benchmark for new physics
• Lepton flavour violation in rare ${\Lambda }_b$ decays
• Prospects for New Physics searches with ${\Lambda }_b\to \Lambda (1520){\ell }^{+}{\ell }^{-}$ decays
• Transition form factors and angular distributions of the ${\mathbf{\Lambda }}_{\mathbf{b}}\to \mathbf{\Lambda }(1520)(\to \mathbf{N}\bar{\mathbf{K}}){\mathbf{\ell }}^{+}{\mathbf{\ell }}^{-}$ decay supported by baryon spectroscopy
• Polarized ${\Lambda }_b$ baryon decay to $p\pi$ and a dilepton pair
• Angular distribution of ${\Lambda }_b^0\to p{K}^{-}{\ell }^{+}{\ell }^{-}$ decays comprising $\Lambda$ resonances with spin up to $\le 5/2$
• Heavy quark expansion of ${\Lambda }_b\to {\Lambda }^{\ast }(1520)$ form factors beyond leading order