This thesis covers several theoretical aspects of WIMP (weakly interacting massive particles) dark matter searches, with a particular emphasis on colliders. It mainly focuses on the use of effective field theories as a tool for Large Hadron Collider (LHC) searches, discussing in detail the issue of their validity, and on simplified dark matter models, which are receiving a growing attention from the physics community. It highlights the theoretical consistency of simplified models, which is essential in order to correctly exploit their potential and for them to be a common reference when comparing results from different experiments. This thesis is of interest to researchers (both theorists and experimentalists) in the field of dark matter searches, and offers a comprehensive introduction to dark matter and to WIMP searches for students and non-experts.

Enrico Morgante graduated in Theoretical Physics at University of Pisa and Scuola Normale Superiore in 2012. He obtained his PhD in 2016 from University of Geneva, Switzerland. Since then, he has been part of the Theory department in DESY, Hamburg, as a post-doc.

Part I: Introduction.- Generalities about Dark Matter.- Part II: Direct and Indirect WIMP Searches.- Direct Detection of Wimps.- Indirect Detection.- Focus on AMS-02 Anti-protons Results.- Part III: LHC Searches.- Dark Matter Searches at the LHC.- The EFT Approach and its Validity.- Simplied Models.- Relic Density.-  Part IV: Complementary Searches in the Simplied Model Framework.- A U(1) Gauge Mediator.- A 750 Gev Pseudo-scalar Mediator.- Conclusions.