Von den Eigenschaften der dunklen Materie zur fundamentalen Theorie
Final Report Abstract
A wide range of astrophysical and cosmological observations show that about 85% of the matter in the Universe reveals itself only via its gravitational influence. The leading hypothesis for the unknown nature of this mysterious ‘dark matter’ (DM) is a new type of elementary particle, with properties necessarily different from any of those currently known. These DM particles are being searched for with astrophysical observatories, at particle colliders and in large underground experiments. Uncovering the particle nature of DM is one of the greatest tasks of fundamental science today; it would both provide important clues for our understanding of the early and present Universe, and extend our knowledge about matter at microscopic scales towards new frontiers. The focus of the Emmy Noether project was to advance in particular astrophysical searches in view of significant expected experimental improvements, and to explore the complementarity with searches at particle colliders and in underground experiments. Signal identification techniques using gamma rays, radio waves as well as cosmic ray antiprotons and positrons were significantly improved with respect to the state of the art, in particular for distinct spectral signatures. The resulting reduction of the astrophysical uncertainties typically associated to such searches led in many cases to the most competitive limits available in the literature. The probably largest resonance, represented also in the general media, was created by the identification of an almost monochromatic gamma-ray signal at 130 GeV in public data of the galactic center, taken by the Fermi gamma-ray telescope. Such a signal had long been awaited as potential ‘smoking gun’ for particle DM and thus triggered substantial follow-up work – until subsequent data and an updated instrument response function saw it fade away. Among the larger field-theoretical achievements are a fully general calculation of leading electroweak corrections to neutralino DM annihilation, and a new method to cross-correlate monochromatic and continuum signals in cosmic rays, based on an extension of the optical theorem. As a result of the project it was also established that cosmic ray searches for DM can close a blind spot of collider searches, namely scenarios with new particles almost degenerate in mass, and that they are in general highly complementary to the ‘direct’ searches performed with large underground detectors. This complementarity was further confirmed in a global fit perspective, with a next generation numerical tool to perform such global fits shortly publicly available. Last but not least, the project resulted in the first DM model that could simultaneously explain all apparent discrepancies between the cosmological concordance model and observations at (sub)galactic scales. While hard to detect with any of the methods mentioned above, a particularly appealing implementation of this idea – where DM interacts both with itself and with sterile neutrinos – may even naturally solve a seemingly unrelated discrepancy between cosmological datasets at low and high redshifts. In summary, no unambiguous DM signal has been identified. The Emmy Noether project has, however, resulted in the currently best available limits on several properties of the putative DM particle. This significantly narrows down the room left for the most commonly considered candidates, paving the way for new theoretical explanations – including the possibility that DM may be self-interacting and leave its particle imprint only in the way matter clusters on cosmological scales, barely visible to any of the traditional search methods. Lasting contributions that will help to single out even vastly subdominant signals in future observations furthermore include improved signal identification techniques, as well as advanced numerical frameworks for the global statistical interpretation of data from different experiments. Chances are thus better than ever to finally find an answer, within the next few years, to the almost century-old DM puzzle.
Publications
- Complementarity of direct dark matter detection and indirect detection through gamma-rays, Phys. Rev. D 83, 045024 (2011)
L. Bergström, T. Bringmann and J. Edsjö
- Constrained Supersymmetry after two years of LHC data: a global view with Fittino, JHEP 1206, 098 (2012)
P. Bechtle, T. Bringmann, et al.
(See online at https://doi.org/10.1007/JHEP06(2012)098) - Dark matter with long-range interactions as a solution to all small-scale problems of ΛCDM cosmology?, Phys. Rev. Lett. 109, 231301 (2012)
L. G. van den Aarssen, T. Bringmann and C. Pfrommer
- Fermi LAT Search for Internal Bremsstrahlung Signatures from Dark Matter Annihilation, JCAP 1207, 054 (2012)
T. Bringmann, X. Huang, A. Ibarra, S. Vogl and C. Weniger
(See online at https://doi.org/10.1088/1475-7516/2012/07/054) - Gamma Ray Signals from Dark Matter: Concepts, Status and Prospects, Phys. Dark Univ. 1, 194 (2012)
T. Bringmann and C. Weniger
(See online at https://doi.org/10.1016/j.dark.2012.10.005) - Indirect dark matter searches as a probe of degenerate particle spectra, Phys. Lett. B 709, 128 (2012)
M. Asano, T. Bringmann and C. Weniger
(See online at https://doi.org/10.1016/j.physletb.2012.02.017) - 130 GeV gamma-ray line and generic dark matter model building constraints from continuum gamma rays, radio, and antiproton data, Phys. Rev. D 87, no. 10, 103509 (2013)
M. Asano, T. Bringmann, G. Sigl and M. Vollmann
(See online at https://doi.org/10.1103/PhysRevD.87.103509) - Significant Enhancement of Neutralino Dark Matter Annihilation from Electroweak Bremsstrahlung, Phys. Rev. Lett. 112, 071301 (2014)
T. Bringmann and F. Calore
(See online at https://doi.org/10.1103/PhysRevLett.112.071301) - Tight bonds between sterile neutrinos and dark matter, JCAP 1407, 042 (2014)
T. Bringmann, J. Hasenkamp and J. Kersten
(See online at https://doi.org/10.1088/1475-7516/2014/07/042) - Updated cosmic-ray and radio constraints on light dark matter: Implications for the GeV gamma-ray excess at the Galactic center, Phys. Rev. D 90, 123001 (2014)
T. Bringmann, M. Vollmann and C. Weniger
(See online at https://doi.org/10.1103/PhysRevD.90.123001)
