A
bstract
We study a novel dark matter production mechanism based on the freeze-in through
semi-production
, i.e. the inverse semi-annihilation processes. A peculiar feature of this scenario is that ...the production rate is suppressed by a small initial abundance of dark matter and consequently creating the observed abundance requires much larger coupling values than for the usual freeze-in. We provide a concrete example model exhibiting such production mechanism and study it in detail, extending the standard formalism to include the evolution of dark matter temperature alongside its number density and discuss the importance of this improved treatment. Finally, we confront the relic density constraint with the limits and prospects for the dark matter indirect detection searches. We show that, even if it was never in full thermal equilibrium in the early Universe, dark matter could, nevertheless, have strong enough present-day annihilation cross section to lead to observable signals.
A
bstract
Theories with more than one scalar field often exhibit phase transitions producing potentially detectable gravitational wave (GW) signal. In this work we study the semi-annihilating
ℤ
3
...dark matter model, whose dark sector comprises an inert doublet and a complex singlet, and assess its prospects in future GW detectors. Without imposing limits from requirement of providing a viable dark matter candidate, i.e. taking into account only other experimental and theoretical constraints, we find that the first order phase transition in this model can be strong enough to lead to a detectable signal. However, direct detection and the dark matter thermal relic density constraint calculated with the state-of-the-art method including the impact of early kinetic decoupling, very strongly limit the parameter space of the model explaining all of dark matter
and
providing observable GW peak amplitude. Extending the analysis to underabundant dark matter thus reveals region with detectable GWs from a single-step or multi-step phase transition.
A number of papers attempt to explain the positron anomaly in cosmic rays, observed by PAMELA and AMS-02, in terms of dark matter (DM) decays or annihilations. However, the recent progress in cosmic ...gamma-ray studies challenges these attempts. Indeed, as we show, any rational DM model explaining the positron anomaly abundantly produces final state radiation and Inverse Compton gamma rays, which inevitably leads to a contradiction with Fermi-LAT isotropic diffuse gamma-ray background measurements. Furthermore, the Fermi-LAT observation of Milky Way dwarf satellites, supposed to be rich in DM, revealed no significant signal in gamma rays. We propose a generic approach in which the major contribution to cosmic rays comes from the dark matter disc and prove that the tension between the DM origin of the positron anomaly and the cosmic gamma-ray observations can be relieved. We consider both a simple model, in which DM decay/annihilate into charged leptons, and a model-independent minimal case of particle production, and we estimate the optimal thickness of DM disk. Possible mechanisms of formation and its properties are briefly discussed.
When building CP-symmetric models beyond the Standard Model, one can impose CP symmetry of higher order. This means that one needs to apply the CP transformation more than two times to get the ...identity transformation, but still the model is perfectly CP-conserving. A multi-Higgs-doublet model based on CP symmetry of order 4, dubbed CP4, was recently proposed and its phenomenology is being explored. Here, we show that the construction does not stop at CP4. We build examples of renormalizable multi-Higgs-doublet potentials which are symmetric under CP8 or CP16, without leading to any accidental symmetry. If the vacuum conserves CP symmetry of order 2k, then the neutral scalars become CP eigenstates, which are characterized not by CP parities but by CP charges defined modulo 2k. One or more lightest states can be the dark matter candidates, which are protected against decay not by the internal symmetry but by the exotic CP. We briefly discuss their mass spectra and interaction patterns for CP8 and CP16.
The DAMPE excess and gamma-ray constraints Belotsky, Konstantin; Kamaletdinov, Airat; Laletin, Maxim ...
PHYSICS OF THE DARK UNIVERSE,
December 2019, 2019-12-00, 2019-12, Letnik:
26
Journal Article, Web Resource
Recenzirano
Odprti dostop
The direct measurements of the cosmic electron–positron spectrum around 1 TeV made by DAMPE have induced many theoretical speculations about possible excesses in the data above the standard ...astrophysical predictions that might have the dark matter (DM) origin. These attempts mainly fall into two categories: (i) DM annihilations (or decays) in the Galactic halo producing the broad spectrum excess; (ii) DM annihilations in the nearby compact subhalo producing the sharp peak at 1.4TeV. We investigate the gamma-ray emission accompanying e+e− production in DM annihilations, as well as various theoretical means to suppress the prompt radiation, such as specific interaction vertices or multi-cascade modes, and conclude that these attempts are in tension with various gamma-ray observations. We show that the DM explanations of the broad spectrum excess tend to contradict the diffuse isotropic gamma-ray background (IGRB), measured by Fermi-LAT, while the nearby subhalo scenario is constrained by nonobservation in the surveys, performed by Fermi-LAT, MAGIC and HESS. We also briefly review other types of gamma-ray constraints, which seem to rule out the DM interpretations of the DAMPE broad spectrum excess as well.
Multi-Higgs models equipped with global symmetries produce scalar dark matter (DM) candidates stabilized by the unbroken symmetry. It is remarkable that a conserved CP symmetry can also stabilize DM ...candidates, provided it is a CP symmetry of order higher than two. CP4 3HDM, the three-Higgs-doublet model with CP symmetry of order 4, is the simplest example of this kind. It contains two mass-degenerate scalar DM candidates ϕ and , each of them being a CP4 eigenstate and, therefore, its own antiparticle. A novel phenomenological feature of this model is the presence of ϕϕ conversion process, which conserves CP. It offers a rare example of DM models in which self-interaction in the dark sector can significantly affect cosmological and astrophysical observables. Here, we explore the thermal evolution of these DM species in the asymmetric regime. We assume that a mechanism external to CP4 3HDM produces an initial imbalance of the densities of ϕ and . As the Universe cools down, we track the evolution of the asymmetry through different stages, and determine how the final asymmetry depends on the interplay between the conversion and annihilation ϕ SM and on the initial conditions. We begin with the analytic treatment of Boltzmann equations, present a detailed qualitative description of the process, and then corroborate it with numerical results obtained using a dedicated computer code. Finally, we check if the model can produce an observable indirect detection signal.
Abstract Theories with more than one scalar field often exhibit phase transitions producing potentially detectable gravitational wave (GW) signal. In this work we study the semi-annihilating ℤ 3 dark ...matter model, whose dark sector comprises an inert doublet and a complex singlet, and assess its prospects in future GW detectors. Without imposing limits from requirement of providing a viable dark matter candidate, i.e. taking into account only other experimental and theoretical constraints, we find that the first order phase transition in this model can be strong enough to lead to a detectable signal. However, direct detection and the dark matter thermal relic density constraint calculated with the state-of-the-art method including the impact of early kinetic decoupling, very strongly limit the parameter space of the model explaining all of dark matter and providing observable GW peak amplitude. Extending the analysis to underabundant dark matter thus reveals region with detectable GWs from a single-step or multi-step phase transition.
We show that models of strongly interacting (SIMP) dark matter built to reproduce the DAMA signal actually cannot account for its time dependence. We discuss the constraints on this type of models ...coming from direct detection experiments and study the propagation of thermalised dark matter particles in the ground for the allowed values of the parameters. We consider a simple 1D diffusion and a more detailed 3D diffusion. In both cases the predicted signal has either the wrong phase of the annual modulation or a much larger amplitude of the diurnal modulation.
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