# Feed-down effect on $\Lambda$ spin polarization

## TL;DR

This paper develops a theoretical framework to quantify how higher-lying strange baryons' decays influence the observed spin polarization of $ ext{ extLambda}$ hyperons, revealing a suppression effect that impacts interpretation of experimental data.

## Contribution

It introduces a comprehensive formalism for calculating feed-down effects on $ ext{ extLambda}$ polarization, incorporating various decay processes and realistic data inputs.

## Key findings

- Feed-down suppresses primordial $ ext{ extLambda}$ polarization.
- The suppression is insufficient to explain the azimuthal-angle discrepancy.
- Framework applicable to other baryons like $ ext{ extXi}^-$ in future experiments.

## Abstract

We develop a theoretical framework to study the feed-down effect of higher-lying strange baryons on the spin polarization of the $\Lambda$ hyperon. In this framework, we consider two-body decays through strong, electromagnetic, and weak processes and derive general formulas for the angular distribution and spin polarization of the daughter particle by adopting the helicity formalism. Using the realistic experimental data as input, we explore the feed-down contribution to the global and the local $\Lambda$ polarizations and find that such a contribution suppresses the primordial $\Lambda$ polarization, which is not strong enough to resolve the discrepancy between the current theoretical and the experimental results on the azimuthal-angle dependence of $\Lambda$ polarization. Our paper may also be useful for the measurement of spin polarization of baryons heavier than $\Lambda$ (e.g., $\Xi^-$) in future experiments.