The missing matter problem: from the dark matter search to alternative hypotheses (original) (raw)

Dark matter is among the most important open problems in both astrophysics and particle physics. Recently, hints of anomalous cosmic-ray spectra found by astroparticle experiments, such as PAMELA, have motivated interesting interpretations in terms of DM annihilation and/or decay. Even if these signatures also have standard astrophysical interpretations, Fermi-LAT electron spectral measurements indicated the presence of an additional positron source, which could be DM annihilation or decay. Searches by the Fermi-LAT for gamma-ray signals have also been performed, along with measurements of the diffuse Galactic and extragalactic gamma-ray emission, providing unprecedented high quality data and statistics which makes crucial to investigate DM in gamma rays. In addition, Imaging Air Cherenkov Telescopes like HESS, MAGIC, and VERITAS have reported on searches for gamma-ray emission from dwarf galaxies. Moreover, CMS and ATLAS experiments at the Large Hadron Collider (LHC) currently in operation at CERN, are giving their first results for supersymmetry searches and for discovering DM in colliders. Concerning direct search of DM, the most stringent limits on the elastic spin-independent WIMP-nucleon cross-section are coming from CDMS-II, EDELWEISS-II and , in particular, XENON100, whereas, recently, the CoGeNT collaboration reported the WIMP candidate signal events exceeding the known backgrounds and results obtained by the DAMA/LIBRA set-up show the model independent annual modulation signature for DM particles. On the other hand, DM and Dark Energy (DE) could be nothing else but the signal that General relativity is not working at large scales (infrared scales) and alternative theories of gravity should be considered in order to fit observations. The issues of Òmissing matterÓ and Òaccelerating universeÓ could be addressed by taking account extensions of General Relativity (e.g. Extended Theories of Gravity) where gravitational interaction works in different ways at different scales. From this point of view, the gravitational sector should be revised without invoking the presence of new ingredients that, up to now, have not been detected at a fundamental level. At ultraviolet scales, the production of massive gravitons would be a test-bed for the theory. This review presents many aspects, from astrophysical observations to particle physics candidates and describes the theoretical and experimental aspects of the DM problem (or missing matter, considering the alternative approaches) in particle physics, astrophysics and cosmology. A brief overview is given of the phenomenology of several dark matter candidates and their expected production mechanisms, basic properties, and implications for direct and indirect detection, particle colliders, and astrophysical observations. A summary of the experimental status is given and the possible scenarios opening with the upcoming are discussed in the context of an approach which combines information from high-energy particle physics with cosmic-ray and traditional astronomical data.