Dark Matter at the International Linear Collider

The International Linear Collider (ILC) is a planned electron-positron colliderwith polarised beams and centre-of-mass energies of up to 500 GeV. By performinghigh-precision measurements of Standard Model observables and searches for newparticles it can complement the potential of the Large Hadron Collider (LHC).One of the most prominent open questions in physics is the nature of dark matter.Weakly Interacting Massive Particles (WIMPs) are possible candidates for darkmatter, which can be searched for at colliders. In this thesis, the expected sensitivityto a WIMP signal at the ILC is explored in a Monte Carlo study. The WIMPs areassumed to be produced in pairs together with a photon from initial state radiation,through which the process can be identied.A detector simulation $\sqrt{s}$ = 500 GeV is performed for the International LargeDetector (ILD) concept, including beam-induced backgrounds and the luminosityspectrum. In comparison to previous studies many aspects of the analysis are treatedin a more realistic way: e.g. the cuts in the event generation have been updated,a complete description of the reconstruction in the crucial forward region has beenadded and the systematic uncertainties of the luminosity spectrum have been fullytreated for the rst time.In order to provide a model-independent WIMP search, the approach of eectiveoperators is chosen to describe the new interaction. The photon energy spectra fordierent signal hypotheses and the distribution of the Standard Model backgroundare used to calculate the expected 5 discovery reach as well as the 2$\sigma$ exclusionlimits. For the example of a vector operator, energy scales of up to 3TeV can betested for WIMP masses $\lesssim$ 250 GeV assuming 20 years of operation. With beampolarisation the sensitivity can be increased and with the help of data sets takenwith dierent polarisation congurations the eect of the systematic uncertaintiescan be signicantly reduced. The role of the forward acceptance for the suppressionof the Bhabha scattering background is quantied.With two dierent approaches, estimates for the sensitivity at other centre-ofmassenergies than the 500 GeV of the full simulation can be calculated. This allowsto provide results for the full ILC programme, e.g. energy scales of up to 1.4TeV canbe probed with an initial stage of the ILC at a centre-of-mass energy of 250 GeV,while energy scales of up to 4.5TeV could be probed $\sqrt{s}$ = 1TeV