Measuring the Mass of Dark Matter at the LHC

TL;DR

This paper evaluates the capability of current kinematic methods at the LHC to distinguish light dark matter particles from neutrinos, estimating a mass threshold around 10 GeV below which differentiation becomes challenging.

Contribution

It provides a Monte Carlo-based estimate of the minimum mass (~10 GeV) needed for dark matter particles to be distinguishable from massless neutrinos at the LHC using kinematic data.

Findings

Mass threshold for distinguishability is approximately 10 GeV.

Distinguishing light dark matter from neutrinos is challenging below this mass.

The result is largely independent of the production mechanism.

Abstract

Many methods have been developed for measuring the mass of invisible particles that only use kinematic information available at hadron colliders. Because a particle is identified by its mass, these methods are critical when distinguishing between dark matter and fake dark matter, where a neutrino or other massless states can mimic a dark-matter signal. However, the uncertainty associated with measuring the mass of an invisible particle could be so large that it is indistinguishable from a neutrino. Monte Carlo is used to estimate lower bounds on how heavy an invisible particle must be in order for it to be distinguishable from a massless one at 95% CL, which we estimate to be O(10 GeV). This result, to a good approximation, is independent of the way the massive final-state particle is produced. If there is a light dark-matter particle with mass O(10 GeV), its presence will be difficult to unambiguously identify at the LHC, using kinematic information alone.