Research Area Dark Matter
Observations indicate that over 80% of all matter in our Universe is unlike the atoms or particles we have discovered so far. It appears dark or invisible, indicating its presence through its gravity, yet its nature and identity remain a fundamental mystery for physics.
The Quantum Universe cluster uses its experimental, observational, and theoretical expertise to hunt for dark matter and probe the possible interactions of dark matter particles in a variety of ways.
Key Questions
- Does dark matter consist of axions/axion-like particles or WIMPs or something else?
- How can we search for dark matter particles through laboratory experiments, datasets and observations?
- Are there new signatures of such particles directly observable by experiments or indirectly via astrophysical observations?
WIMPs (weakly interacting massive particles) are dark matter candidates generally expected to lie in the mass range GeV (a proton mass) to TeV (5 times the mass of lead nucleus), which can also address the electro-weak scale heirarchy problem.
Dark matter (DM) particles can be created at particle collider experiments where the invisible dark matter particles would show up as missing transverse momentum. Particle collider searches for dark matter of various kinds have been performed and predictions of new signatures for light DM have been done in the context of the Belle II, ATLAS and CMS experiments, and for the proposed LUXE experiment. Light dark sectors have also been theoretically investigated for their underlying particle physics, cosmological aspects, self-interactions, nucleosynthesis constraints and novel ways to achieve the DM relic abundance. Heavy dark sectors have been probed via background studies for monojet search for ATLAS, invisible Higgs decays, signatures associated with top quarks, extended Higgs sectors or supersymmetry. Contributions have also been made to direct detection DM searches in underground low-background experiments like NEWS-G and SuperCDMS.
LOFAR radio telescope observations of dwarf spheroidal galaxies have searched for synchrotron radiation from WIMP self-annihilation, placing the some of the strongest constraints yet on the WIMP cross section into electron positron pairs, especially at low masses. Novel simulations of DM halos, satellites and merging galaxy clusters have been pioneered for self-interacting dark matter. Incorporating new effects like frequent small-angle as well as velocity-dependent scatterings, these simulations reveal the potential of DM-galaxy offsets, collisionless tracers and diversity of rotation curves to probe the physics of interacting dark matter. Preparations for the WAVES galaxy survey are underway which will probe the DM halo mass function down to low masses and small scales to constrain DM models. Astroparticle data will be used from the under-construction CTA and TAIGA hybrid air shower array for indirect high mass DM search.
Axions and WISPs (weakly interacting sub-eV particles) are extremely light dark matter candidates are generally expected to have masses between a milli-eV (109 times lighter than an electron) to 10-22 eV where the wave nature of ultra-light DM becomes important on Galactic scales. Axions can also solve the strong CP problem.
A unique platform for axion and WISP searches is being established at Hamburg with the construction and commissioning of several novel experiments: BRASS, MADMAX and babyIAXO complement existing experiments such as WISPDMX and ALPS II all located at the Campus Bahrenfeld. Both theoretical and experimental groups have contributed substantially to developing specific ideas for these experiments which convert axions to photons in strong magnetic fields.
The BRASS and MADMAX experiments will both search for the strongly motivated QCD axion DM in its less explored mass range of 10 to several hundred micro-eV. Complementary to axion DM searches, the babyIAXO (and later IAXO) experiment will search for solar axions, streaming to us from the Sun's core. BabyIAXO's sensitivity augments the currently underway ALPS II experiment which looks for axion-like particles generated in the lab by shining laser light through a wall via photon-axion conversion and subsequent reconversion. New experimental approaches like cryogenic detection, a resonating LC-circuit in the WISPLC experiment and a fiber-interferometer in the WISPFI experiment are also extending the mass range and coupling reach for axions and axion-like particles.
Axion-related theory and phenomenology has produced new models that extend the canonical QCD axion band for solving the strong CP problem with important implications for axion-like particle experiments. Alternative axion production mechanisms such as trapped misalignment and axion fragmentation have been worked out. The prospects for their observational tests and relaxation of the electroweak scale have been studied. Star-like solutions of axion-like particles interacting gravitationally have also been investigated. Indirect astrophysical searches also look for axion signatures like spectral oscillation features using new approaches.
Theoretical work and simulations have also investigated dilute and pair-beam plasma in the context of laboratory astrophysics. This connects to observed hints for axion-like particles from cosmic transparency as well as to our understanding of the origin and distribution of magnetic fields in the Universe. Observational work on the latter has consisted of studies of cosmic magnetic fields in our Galaxy, in clusters and filaments. Together with studies of turbulent dynamo amplification, this can constrain the primordial origin for magnetic fields.
People Involved
Area Coordinator: Kai Schmidt-Hoberg
Principal Investigators: Katharina Behr, Marcus Brüggen, Freya Blekman, Erika Garutti, Alexander Grohsjean, Florian Grüner, Caren Hagner, Johannes Haller, Sarah Heim, Beate Heinemann, Dieter Horns, Gregor Kasieczka, Axel Lindner, Jochen Liske, Jan Louis, Gudrid Moortgat-Pick, Andreas Ringwald, Peter Schleper, Christian Schwanenberger, Géraldine Servant, Günter Sigl, Georg Weiglein, Alexander Westphal
Key Researchers: Juliette Alimena, David Berge, Katharina Isleif, Andreas Maier, Manuel Meyer, Krisztian Peters, Martin Pohl, Frank Tackmann