Physics performance for Dark Matter searches at √s = 3 TeV at CLIC using mono-photons and polarised beams.

At e− e+ colliders, Weakly Interacting Massive Particles (WIMPs) are candidates for dark matter (DM) and can be searched for using as tag a photon from initial state radiation. The potential for detecting DM at the Compact Linear Collider (CLIC) is investigated at sqrt(s) = 3 TeV. The sensitivity of the search is estimated by computing the 95% confidence level upper limit cross section as a function of the dark matter mass. Left-handed (right- handed) polarised e− beams increase (decrease) respectively the Standard Model back- grounds and are essential to characterize the WIMPs properties and control the systematic errors. Using right-handed polarised e− beams is decreasing significantly the 95% con- fidence level cross section. Using the ratio of the energy distributions for left-handed and right-handed polarised e− beams, systematic errors cancel out. Computing the 95% confid- ence level upper limit cross section using the ratio requires a model assumption to compute the expected number of signal events. Exclusion limits for dark matter are derived using dark matter Simplified Models for two values of the e-e-mediator vertex coupling, a medi- ator width of 10 GeV and for a fixed value of the mediator-DM-DM coupling. For a mediator mass of 3.5 TeV, the measurement of the differential distribution of the significance as a function of the photon energy for the process e− e+ → X X γ allows the discrimination between different dark matter mediators and the measurement of the WIMP mass to nearly half the centre-of-mass energy. For a 1 TeV WIMP, the mass is determined with a 1% accuracy.