Viktor Kutzner

This document is the final report of the ATLAS-CMS Dark Matter Forum, a forum organized by the ATLAS and CMS collaborations with the participation of experts on theories of Dark Matter, to select a minimal basis set of dark matter simplified models that should support the design of the early LHC Run-2 searches. A prioritized, compact set of benchmark models is proposed, accompanied by studies of the parameter space of these models and a repository of generator implementations. This report also addresses how to apply the Effective Field Theory formalism for collider searches and present the results of such interpretations.

This thesis presents the search for new physics in the mono-electron channel using proton-proton collision data with a center-of-mass energy of √ s = 13 TeV recorded at the LHC in 2015 by the CMS experiment. The recorded data is compared to the Standard Model prediction in the transverse mass distribution. The deviations between data and the Standard Model prediction are analyzed in terms of interpretations be- yond the Standard Model. The interpretations include the production of a heavy W′ vector boson and the production of dark matter through simplified models. The data is interpreted as 95% CL exclusion limits. The production of a W′ boson can be excluded for masses up to 3.75 TeV. Simplified models are used to model the dark matter production mechanism. The sensitivity of this study is presented in terms of excluded mediator masses Mmed and dark matter masses mDM for axial-vector, vector, scalar and pseudoscalar coupling mediator models. The influence of the future High-Luminosity LHC upgrade on the dark matter search in the mono-electron channel is investigated, along with CMS detector upgrades. The increased sensitivity is evaluated for a simplified model with an axial-vector coupling mediator.

The current status of the searches for exotic, long-lived particles with the CMS experiment at $\sqrt{s}=13$ TeV is presented. Many theories beyond the Standard Model predict long-lived particles, for which different search approaches are utilized from those used in prompt searches. The searches discussed include the latest results at the time of the conference and cover a wide range of signatures. Searches for exotic, long-lived particles using inclusive displaced jets, displaced vertices in multijet events, disappearing tracks, heavy stable charged particles, and stopped particles are discussed, as well as reinterpretations of two recently published prompt searches, which complement the dedicated searches. The search and results are summarized for each analysis.