Spin Discrimination in Three-Body Decays

TL;DR

This paper explores how to determine the spins of new particles involved in three-body decays at colliders, especially when one escapes detection, using invariant mass distributions and a model-independent approach.

Contribution

It introduces a novel, model-independent method to identify particle spins in three-body decay scenarios with missing energy at the LHC.

Findings

Effective spin determination in heavy intermediate particle scenarios

Model-independent strategy successfully tested with Monte Carlo simulations

Potential to distinguish between different new physics models

Abstract

The identification of the correct model for physics beyond the Standard Model requires the determination of the spin of new particles. We investigate to which extent the spin of a new particle $X$ can be identified in scenarios where it decays dominantly in three-body decays $X\to f\bar{f} Y$. Here we assume that $Y$ is a candidate for dark matter and escapes direct detection at a high energy collider such as the LHC. We show that in the case that all intermediate particles are heavy, one can get information on the spins of $X$ and $Y$ at the LHC by exploiting the invariant mass distribution of the two standard model fermions. We develop a model-independent strategy to determine the spins without prior knowledge of the unknown couplings and test it in a series of Monte Carlo studies.