# Coherent helicity amplitude for sequential decays

## TL;DR

This paper derives a method for calculating coherent helicity amplitudes in sequential decays involving particles with spin, enabling more accurate interference analysis in partial wave studies.

## Contribution

It introduces a systematic way to include rotations for helicity amplitudes, improving the coherence and consistency in decay chain analyses.

## Key findings

- Rotations significantly affect interference patterns in decay chains.
- The method enhances the accuracy of partial wave analysis.
- Coherent amplitudes allow for proper combination of different decay pathways.

## Abstract

We present a derivation of coherent helicity amplitudes for a particle decaying into multifinal states with nonzero spins. The results show that the coherent amplitudes introduce additional rotations to transform the helicities into a consistent helicity system, which allows us to add helicity amplitudes for different decay chains coherently. These rotations may have significant effects on the interference between the decay chains in the partial wave analysis.