Investigating the Dark Matter of the Universe

• Applicant: Professor Dr. Wim de Boer (†)
• Subject Area: Nuclear and Elementary Particle Physics, Quantum Mechanics, Relativity, Fields ; Astrophysics and Astronomy
• Term: from 2015 to 2018
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 263859030

Cosmologists found out that more than 80% of the matter in the universe is invisible. One usually assumes that this Dark Matter consists of particles, but their nature is still unknown. These DM particles interact only via gravity or the weak force. Therefore they must have mass and are generically called WIMPS (Weakly Interacting Massive Particles). Several WIMP candidates exist: massive neutrinos, axions and neutralinos. The DM may well be a mixture of them. The known neutrinos have a too low mass to contribute significantly to the dark matter, as is known from cosmology. To search for the nature of dark matter is one of the outstanding research goals in the interdisciplinary field of particle physics, astroparticle physics and cosmology. We want to investigate, if neutralinos dominate the DM, as is usually assumed. Neutralinos are the WIMP candidates from Supersymmetry (SUSY). The high popularity of Supersymmetry stems from the fact that it solves several flaws of the Standard Model (SM) at once and allows for unification of all SM forces in a Grand Unified Theory. SUSY predicts WIMP annihilation and elastic scattering of WIMPs on nuclei. These signatures are the basis for the indirect and direct DM searches. Annihilation in our Galaxy will lead to anomalous gamma ray spectra and an excess of antimatter, which can be searched for with particle detectors in space. Elastic scattering has an exceedingly small cross section, so direct DM searches can be performed only in deep underground laboratories, where the background from cosmic ray interactions is reduced. No clear WIMP signals have been found so far in experiments, except for the fact that data from the Fermi-LAT satellite show a small hint for a 25 GeV WIMP annihilation signal in the gamma-ray spectra from local dwarf galaxies. We want to analyze the public Fermi-LAT data using novel methods from particle physics, which allow to determine the background and a possible signal simultaneously. In a preliminary analysis we find indeed a strong hint for a 30 GeV WIMP signal compatible with the small excess from the dwarf galaxies. Drawing conclusions requires investigating all possible sources of systematic errors from background uncertainties, which will be the major work of this project. In addition, we want to compare gamma-ray data from the AMS-02 experiment on the International Space Station with the Fermi-LAT data. Finally, we want to compare these results with searches for Supersymmetry at the Large Hadron Collider, the powerful accelerator at the European Particle Physics Laboratory at CERN, Geneva. At the LHC WIMPs may be produced directly or one obtains hints for SUSY from anomalous couplings of the newly discovered Higgs boson.

• DFG Programme: Research Grants