Novel method to deal with off-shell particles in cascade decays

TL;DR

This paper introduces a new algorithm for calculating decay widths involving off-shell particles in cascade decays, applicable to particles of various spins, and verified against existing analytical results.

Contribution

The paper presents a novel, automatable algorithm for computing decay widths with off-shell particles across different spins, improving phase space calculations for complex decays.

Findings

Results match existing analytical calculations

Applicable to particles with spins 0, 1/2, and 1

Can be used without Monte Carlo sampling

Abstract

We propose a novel algorithm to compute the width of any generic $n$-body decay involving multiple off-shell particles having zero and non-zero spins. Starting from a toy example, we show the computations for three different processes that contain spin-0, $\frac{1}{2}$, and 1 off-shell particles. We have checked that our results match with the existing results at the analytical level. This proposal can be automatized and should be useful to compute the phase space for long cascade decays, without any Monte Carlo sampling.