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Special Issue – Composite Dark Matter
Khlopov, Maxim; Belotsky, Konstantin; Cudell, Jean-René et al.
2015World Scientific
 

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Keywords :
Dark matter; Cosmology; Particle physics
Abstract :
[en] Modern astronomical observations favor the existence of dark matter as the necessary element of the modern theory of the Universe. The measured deficit of baryonic matter as compared to the measured total matter content of the Universe implies that dark matter should be nonbaryonic. This phenomenon cannot be grounded in the known laws of physics and calls for hypothetical new particles and fields predicted by extensions of the Standard Model of elementary particles. In the context of cosmology, dark matter stems from the processes in the early Universe that create this new form of matter, which is then sufficiently stable to survive to the present day. In the context of particle theory, the stability of dark matter implies new conservation laws, resulting from new fundamental symmetries. The simplest candidates for dark matter, such as neutral Weakly Interacting Massive Particles (WIMPs), have difficulty explaining the results of direct and indirect experimental searches for dark matter particles as well as the astronomical observations of dark-matter distribution and structure. This is why a wide variety of other more sophisticated solutions for the dark matter problem are being considered and composite dark matter is of special interest among them. In a similar way, as the ordinary matter, composed of electrons and nucleons, represents a wide variety of composite objects and structures, the physical content of dark matter may also be far from elementary. In 2014 we have invited investigators to contribute original research and review articles that seek to define the possible physical nature of dark atoms and their constituents, to stimulate the experimental searches and to suggest astrophysical tests for their effects, what gave rise to the special issue ``Dark Atoms and Dark Radiation" of Advances in High Energy Physics. However, dark atoms exhibit only one possible aspect of the composite dark matter problem and we turn to more general discussion of this problem in the present issue. The collected papers in this special issue represent only a small step in the approach to a thorough investigation of composite dark matter, demonstrating the wide but far from complete variety of possible aspects of this problem. The papers in this volume discuss composite dark matter candidates from extra dimensions or mini-black hole bound systems to atom-like bound states of new stable electrically charged particles. Pending on their type, dark atom constituents may be bound by ordinary Coulomb and chromo-Coulomb interactions, gravitation or by some new forces. Even if composite dark matter acts on ordinary matter through its gravity only, as in the case of black holes, their presence in the Universe can lead to observable consequences. The signatures of their presence can be probed in the studies of cosmic rays and gamma radiation, if these constituents possess electric charge or can decay to ordinary charged particles. In particular, the excessive intensity of the positron annihilation line in the galactic bulge, observed by INTEGRAL, can find explanation by de-excitation of dark atoms, colliding in the central part of the Galaxy. This explanation revealed a very strong dependence on the still uncertain density and velocity distribution of dark matter in this region. Recent estimations of these astrophysical parameters can limit the mass of doubly charged dark atom constituents within a very narrow range. Composite dark matter may be multi-component and the existence of even a strongly subdominant component can be probed in direct and indirect dark matter searches. Moreover, in the present issue, a possibility to explain the excess of cosmic high-energy positrons, observed by PAMELA, FERMI-LAT and AMS02, via decays of metastable doubly-charged-dark-atom constituents has been proved. Such possibilities imply restricted ranges of masses for (meta)stable doubly charged particles, challenging accelerator searches. We thank all the authors for their contributions to the present issue and express the hope that its publication will stimulate further extensive discussions of this exciting topic.
Research center :
STAR Institute
Disciplines :
Physics
Editor :
Khlopov, Maxim;  Université Paris Diderot - Paris 7 > APC Laboratory
Belotsky, Konstantin;  Moscow Engineering and Physics Institute (MEPhI)
Cudell, Jean-René  ;  Université de Liège > Département d'astrophys., géophysique et océanographie (AGO) > Inter. fondamentales en physique et astrophysique (IFPA)
Kouvaris, Chris;  University of Southern Denmark > CP3-origins
Language :
English
Title :
Special Issue – Composite Dark Matter
Publication date :
November 2015
Publisher :
World Scientific
Edition :
Volume: 24, Number: 13
Collection name :
International Journal of Modern Physics D,
Available on ORBi :
since 06 July 2016

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