Using Energy Peaks to Count Dark Matter Particles in Decays

TL;DR

This paper introduces a novel method using energy spectrum peaks to determine the number of dark matter particles produced in collider decays, aiding in identifying the underlying stabilization symmetry.

Contribution

It presents a new approach based on energy spectrum analysis to distinguish between two- and three-body decays involving dark matter particles at colliders.

Findings

The method successfully differentiates decay modes with one or two DM particles.

Theoretical results on energy distributions of three-body decays support the method.

Application to bottom quark partner decays demonstrates practical feasibility.

Abstract

We study the determination of the symmetry that stabilizes a dark matter (DM) candidate produced at colliders. Our question is motivated per se, and by several alternative symmetries that appear in models that provide a DM particle. To this end, we devise a strategy to determine whether a heavy mother particle decays into one visible massless particle and one or two DM particles. The counting of DM particles in these decays is relevant to distinguish the minimal choice of Z_2, from a Z_3, stabilization symmetry, under which the heavy particle and the DM are charged and the visible particle is not. Our method is novel in that it chiefly uses the peak of the energy spectrum of the visible particle and only secondarily uses the M_T2 endpoint of events in which the heavy mother particles are pair-produced. We present new theoretical results concerning the energy distribution of the decay products of a three-body decay, which are crucial for our method. To demonstrate the feasibility of our method in investigating the stabilization symmetry, we apply it in distinguishing the decay of a bottom quark partner into a b quark and one or two DM particles. The method can be applied generally to distinguish two- and three-body decays, irrespective of DM.