About 27% of the total energy density in the universe consists of dark matter, while baryonic matter, which is the matter we know and that forms all the stars and galaxies, makes up only 5%. Dark matter represents one of the unsolved problems in physics. Its existance is considered to be proven by various observations of gravitational effects on baryonic matter but the particle nature of dark matter is unknown, making it one of the greatest mysteries in particle physics.
Many theories predict dark matter to be light enough to be produced pairwise in proton-proton collisions at the LHC. Unfortunately, it is not possible to detect it in a direct way. However, there is a way out: dark matter may be discovered via radiation of additional particles such as W or Z bosons along with missing energy.
Our group is searching for events with dark matter candidates in which either an additional Z boson is produced (A. Meyer, A. Albert et al.) that decays into a pair of charged leptons, or a further W boson appears (K. Hoepfner et al.), leaving a signature of a charged lepton and missing transverse energy.