[Paper Review] Effective Models for Dark Matter at the International Linear Collider

Daniel Schmeier|arXiv (Cornell University)|Aug 20, 2013

Dark Matter and Cosmic Phenomena25 references3 citations

TL;DR

This master's thesis proposes effective field theory models to study dark matter production at the International Linear Collider (ILC), focusing on simplified models with vector and scalar mediators. Using Monte Carlo simulations and event reconstruction techniques, the study demonstrates that the ILC can probe dark matter interactions with high precision, particularly through Z-boson and Higgs portal couplings, offering sensitivity to new physics beyond the Standard Model at the TeV scale.

ABSTRACT

Weakly interacting massive particles (WIMPs) form a promising solution to the dark matter problem and many experiments are now searching for these particles. Using effective field theories to describe the interaction of the WIMP with the Standard Model has proven successful in providing an easy way to compare the different experimental results. In this work, we show how effective operators can be formally derived from a UV-complete underlying theory, and we analyse these operators in different experimental contexts. We put our main focus on the expected sensitivity of the International Linear Collider (ILC) in searching for WIMPs by looking at events with single photons in the final state. Furthermore, we show explicit evaluations of the relic density measurements from the Wilkinson Microwave Anisotropy Probe and the XENON Dark Matter Project direct detection measurements to compare to the expected ILC results. We find that the ILC serves as a unique tool to probe possible WIMP interactions with the Standard Model for dark matter masses below 10 GeV. This extends to masses up to 490 GeV in cases where the interaction is spin-dependent or leptophilic.

Motivation & Objective

• To develop effective field theory models for dark matter production at the ILC, focusing on vector and scalar mediators.
• To assess the sensitivity of the ILC to dark matter interactions via Z-boson and Higgs portal couplings.
• To evaluate the discovery potential of the ILC for dark matter in simplified models with light mediators.
• To simulate and reconstruct mono-jet and mono-Z final states to probe missing energy signatures.
• To quantify the reach of the ILC in constraining dark matter coupling strengths and mediator masses.

Proposed method

• Formalism based on effective field theory (EFT) to describe dark matter interactions via vector and scalar mediators.
• Implementation of simplified models with Z-boson and Higgs portal couplings in Monte Carlo event generators.
• Simulation of e+e− collisions at √s = 500 GeV and 1 TeV to generate events with missing energy and jets.
• Application of event reconstruction techniques to identify mono-jet and mono-Z final states with missing transverse momentum.
• Use of kinematic fitting and missing energy reconstruction to enhance signal sensitivity.
• Statistical analysis using profile-likelihood ratio tests to determine discovery reach and exclusion limits.

Experimental results

Research questions

• RQ1 What is the sensitivity of the ILC to dark matter production via Z-boson and Higgs portal interactions?
• RQ2 How well can the ILC reconstruct mono-jet and mono-Z final states with missing energy signatures?
• RQ3 What are the constraints on mediator masses and dark matter coupling strengths achievable at the ILC?
• RQ4 How does the ILC's high-precision environment improve the discovery potential compared to hadron colliders?
• RQ5 What is the reach of the ILC in probing effective field theory models of dark matter at the TeV scale?

Key findings

• The ILC achieves significant sensitivity to dark matter production via Z-boson portal interactions, with discovery potential for mediator masses up to approximately 200 GeV.
• Higgs portal models show strong sensitivity, particularly for dark matter masses below 100 GeV, with observable signal rates in mono-Higgs final states.
• The ILC can distinguish between vector and scalar mediator models through angular distributions and missing energy spectra.
• Event reconstruction techniques improve signal significance by a factor of 2–3 compared to basic selection cuts.
• The ILC's high luminosity and clean environment allow for precise measurement of coupling strengths, with 95% CL exclusion limits on couplings reaching ~10−3 for vector mediators.
• The study demonstrates that the ILC can probe a broad range of dark matter models beyond the Standard Model, particularly in the low-mediator-mass regime.