Dark Matter Models: Signals and Backgrounds at the LHC and Future Colliders

Abstract

We explore the phenomenological signals and potential backgrounds of various Minimal Consistent Dark Matter (MCDM) models in the context of the Large Hadron Collider (LHC), non-LHC and future collider experiment searches. We study two key background processes to Dark Matter (DM), and indeed more general beyond the Standard Model (BSM) physics, at the LHC as part of the ATLAS collaboration. For the production of Z boson in association with high pT jets, we present results for data-driven t ¯t modelling and multi-jet background derivation. We also investigate non-perturbative correction, and comparisons of our Monte Carlo generator results from the analysis’ Rivet routine. For the production of Z boson in association with heavy flavour quarks (i.e. b and c quarks) we present a novel approach to jet flavour discrimination through a fitting algorithm. We explore the full parameter space and provide new LHC limits for both inert 2-Higgs Doublet Model (i2HDM) scalar DM and Minimal Fermionic DM (MFDM) at 13 TeV through a multilepton+missing ET analysis. We parametrise in terms of mass splits, providing a more intuitive picture of the underlying physics in addition to a no-lose theorem in MFDM. We find significant contributions to sensitivity from 3-lepton final states. These limits and efficiencies we provide can then be extrapolated and applied in a model-independent way. We additionally study non-LHC constraints from relic density requirements, direct and indirect detection, including Cosmic Microwave Background (CMB) and future Cherenkov Telescope Array (CTA) projections. These are combined for a comprehensive picture of the MFDM model, in addition to a summary of the i2HDM limits. We utilise a model independent method for discriminating DM mass at future e +e − colliders, by analysing the energy distributions of charged DM decay products in D± → W±D1 cascades. We apply this to the i2HDM and MFDM models with two example benchmark points that provide correct observed DM density and comply with direct detection experimental bounds. We additionally present a method for discriminating DM spin by observing angular distributions of W± from reconstructed dijets.