# Angular analysis of the rare decay $\Lambda_b\to \Lambda(1520)(\to NK)\ell^+\ell^-$

## TL;DR

This paper analyzes the angular distribution of the rare decay $oldsymbol{ ext{Lambda}_b o ext{Lambda}(1520) ( o NK) ext{l}^+ ext{l}^-}$ to explore potential new physics effects in $b o s ext{l}^+ ext{l}^-$ transitions, providing a comprehensive theoretical framework.

## Contribution

It offers the first detailed angular analysis of this decay mode, expressing observables in terms of helicity amplitudes and exploring sensitivity to new physics using quark model inputs.

## Key findings

- Derived angular observables in terms of helicity amplitudes.
- Identified potential sensitivity of observables to new physics contributions.
- Provided relations among hadronic form factors at different recoil regimes.

## Abstract

We study the differential decay rate for the rare decay $\Lambda_b\to \Lambda(1520)(\to NK)\ell^+\ell^-$ where $\ell$ is a light lepton, as this decay mode can provide new and complementary constraints on the Wilson coefficients in $b\to s\ell^+\ell^-$ transitions compared to other modes. We provide a determination of the complete angular distribution, assuming unpolarised $\Lambda_b$ 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 $\Lambda$ 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.