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Register a new userParticle Dark Matter Candidates
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M.Yu. Khlopov
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A series of brief reviews collected in the present issue present various candidates for cosmological Dark Matter (DM) predicted by models of particle physics. The range from superlight axions to extended objects is covered. Though the possible list of candidates is far from complete it gives the flavor of the extensive field of Dark matter particle physics.
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micrOMEGAs is a code to compute dark matter observables in generic extensions of the standard model. This version of micrOMEGAs includes a generalization of the Boltzmann equations to take into account the possibility of two dark matter candidates. The modification of the relic density calculation to include interactions between the two DM sectors as well as semi-annihilation is presented. Both DM signals in direct and indirect detection are computed as well. An extension of the standard model with two scalar doublets and a singlet is used as an example.
We revisit the possibility of light scalar dark matter, in the MeV to GeV mass bracket and coupled to electrons through fermion or vector mediators, in light of significant experimental and observational advances that probe new physics below the GeV-scale. We establish new limits from electron colliders and fixed-target beams, and derive the strength of loop-induced processes that are probed by precision physics, among other laboratory probes. In addition, we compute the cooling bound from SN1987A, consider self-scattering, structure formation, and cosmological constraints as well as the limits from dark matter-electron scattering in direct detection experiments. We then show that the combination of constraints largely excludes the possibility that the galactic annihilation of these particles may explain the long-standing INTEGRAL excess of 511 keV photons as observed in the galactic bulge. As caveat to these conclusions we identify the resonant annihilation regime where the vector mediator goes nearly on-shell.
In these brief lecture notes, we introduce sterile neutrinos as dark matter candidates. We discuss in particular their production via oscillations, their radiative decay, as well as possible observational signatures and constraints.
We review the physics case for very weakly coupled ultralight particles beyond the Standard Model, in particular for axions and axion-like particles (ALPs): (i) the axionic solution of the strong CP problem and its embedding in well motivated extensions of the Standard Model; (ii) the possibility that the cold dark matter in the Universe is comprised of axions and ALPs; (iii) the ALP explanation of the anomalous transparency of the Universe for TeV photons; and (iv) the axion or ALP explanation of the anomalous energy loss of white dwarfs. Moreover, we present an overview of ongoing and near-future laboratory experiments searching for axions and ALPs: haloscopes, helioscopes, and light-shining-through-a-wall experiments.
Dark matter made from non-thermally produced bosons can have very low, possibly sub-eV masses. Axions and hidden photons are prominent examples of such dark very weakly interacting light (slim) particles (WISPs). A suitable mechanism for their non-thermal production is the misalignment mechanism. Their dominant interaction with Standard Model (SM) particles is via photons. In this note we want to go beyond these standard examples and discuss a wide range of scalar and pseudo-scalar bosons interacting with SM matter fermions via derivative interactions. Suitably light candidates arise naturally as pseudo-Nambu-Goldstone bosons. In particular we are interested in examples, inspired by familons, whose interactions have a non-trivial flavor structure.
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