Prospects for discovery and spin discrimination of dark matter in Higgs portal DM models and their extensions at 100 TeV $pp$ collider

TL;DR

This paper evaluates the potential for discovering and distinguishing the spin of dark matter particles in Higgs portal models at a future 100 TeV proton-proton collider, using specific production channels and kinematic variables.

Contribution

It introduces a method to discriminate dark matter spin and assesses discovery prospects in Higgs portal models at a 100 TeV collider with detailed analysis of kinematic distributions.

Findings

Discovery/exclusion possible with less than 1 ab$^{-1}$ luminosity.

Spin discrimination requires a few tens of ab$^{-1}$ luminosity.

Effective background suppression techniques are identified.

Abstract

We study the discovery and discriminating prospects of the Higgs portal dark matter (DM) models for scalar, fermion and vector DM and their extensions in proton-proton ($pp$) collisions. The $t\bar{t}+$DM associated production in dileptonic final states is considered, in which the stransverse mass of two leptons is found to be effective in suppressing the Standard Model backgrounds along with the missing transverse energy and the angle between two leptons. The distributions of missing transverse energy and polar angle between two leptons are used for a discrimination of the spin nature of DM. For the proposed benchmark points, the discovery/exclusion can be made with an integrated luminosity less than 1 ab$^{-1}$ given a 1\% systematic uncertainty, while the spin discrimination require integrated luminosity of a few O(10) ab$^{-1}$ given a 0.5\% systematic uncertainty. The DM phenomenology is also discussed. A consistent DM candidate can be obtained either by extending our model where the Higgs portal couples to excited dark states that decay into DM, or modifying the coupling form into pseudoscalar.