Ordered Kinematic Endpoints for 5-body Cascade Decays

TL;DR

This paper derives kinematic endpoints for 5-body cascade decays with various decay modes, introducing techniques to find sub-leading endpoints that offer additional constraints on particle mass spectra.

Contribution

It provides new expressions for kinematic endpoints in complex 5-body decay chains and methods to determine sub-leading endpoints for indistinguishable invariant masses.

Findings

Derived expressions for 5-body decay kinematic endpoints

Introduced techniques for sub-leading endpoint determination

Sub-leading endpoints provide independent mass constraints

Abstract

We present expressions for the kinematic endpoints of 5-body cascade decay chains proceeding through all possible combinations of 2-body and 3-body decays, with one stable invisible particle in the final decay stage. When an invariant mass can be formed in multiple ways by choosing different final state particles from a common vertex, we introduce techniques for finding the sub-leading endpoints for all indistinguishable versions of the invariant mass. In contrast to short decay chains, where sub-leading endpoints are linearly related to the leading endpoints, we find that in 5-body decays, they provide additional independent constraints on the mass spectrum.