Angular analysis of the rare decay \( {\Lambda}_b\to \Lambda (1520)\left(\to N\overline{K}\right){\ell}^{+}{\ell}^{-} \)


We study the differential decay rate for the rare decay \( {\Lambda}_b\to \Lambda (1520)\left(\to N\overline{K}\right){\ell}^{+}{\ell}^{-} \) where is a light lepton and \( N\overline{K}=p{K}^{-} \),\( n{\overline{K}}^0 \), as this decay mode can provide new and complementary constraints on the Wilson coefficients in bsℓ+ transitions compared to other modes. We provide a determination of the complete angular distribution, assuming unpolarised Λb baryons and neglecting the lepton mass. The resulting angular observables are expressed in terms of helicity amplitudes involving hadronic form factors within the Standard Model and New Physics models with chirality-flipped operators. We study these observables at low and large Λ recoils, using effective theories to determine relations among the hadronic form factors involved. As there is currently no determination of the form factors available from lattice simulations or light-cone sum rules, we perform a first illustration of the sensitivity of some observables to New Physics contributions using hadronic inputs from quark models.

A preprint version of the article is available at ArXiv.

Change history

  • 16 June 2020

    We provide corrections to section 2, section 4 and appendix A of ref. [1]. We update the numerical results of ref. [1] with the latest results from ref. [2].


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Descotes-Genon, S., Brunet, M.N. Angular analysis of the rare decay \( {\Lambda}_b\to \Lambda (1520)\left(\to N\overline{K}\right){\ell}^{+}{\ell}^{-} \). J. High Energ. Phys. 2019, 136 (2019).

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  • Heavy Quark Physics
  • Beyond Standard Model
  • Effective Field Theories