scholarly journals Dark matter relic abundance beyond kinetic equilibrium

2021 ◽  
Vol 81 (7) ◽  
Author(s):  
Tobias Binder ◽  
Torsten Bringmann ◽  
Michael Gustafsson ◽  
Andrzej Hryczuk
Keyword(s):  
Dark Matter ◽  
Space Distribution ◽  
Number Density ◽  
Dark Matter Annihilation ◽  
The Public ◽  
Relic Density ◽  
Order Of Magnitude ◽  
Numerical Precision ◽  
Relic Abundance ◽  
Kinetic Equilibrium

AbstractWe introduce , a numerical precision tool for predicting the dark matter relic abundance also in situations where the standard assumption of kinetic equilibrium during the freeze-out process may not be satisfied. comes with a set of three dedicated Boltzmann equation solvers that implement, respectively, the traditionally adopted equation for the dark matter number density, fluid-like equations that couple the evolution of number density and velocity dispersion, and a full numerical evolution of the phase-space distribution. We review the general motivation for these approaches and, for illustration, highlight three concrete classes of models where kinetic and chemical decoupling are intertwined in a way that quantitatively impacts the relic density: (i) dark matter annihilation via a narrow resonance, (ii) Sommerfeld-enhanced annihilation and (iii) ‘forbidden’ annihilation to final states that are kinematically inaccessible at threshold. We discuss all these cases in some detail, demonstrating that the commonly adopted, traditional treatment can result in an estimate of the relic density that is wrong by up to an order of magnitude. The public release of , along with several examples of how to calculate the relic density in concrete models, is provided at drake.hepforge.org

scholarly journals Dark matter freeze-in from semi-production

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Andrzej Hryczuk ◽  
Maxim Laletin
Keyword(s):  
Dark Matter ◽  
Early Universe ◽  
Cross Section ◽  
Thermal Equilibrium ◽  
Indirect Detection ◽  
Production Mechanism ◽  
Number Density ◽  
Matter Production ◽  
Relic Density ◽  
Standard Formalism

Abstract 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.

scholarly journals Dark matter annihilation in the universe

2014 ◽  
Vol 30 ◽  
pp. 1460256 ◽  
Author(s):  
Pierre Salati
Keyword(s):  
Dark Matter ◽  
Galactic Halo ◽  
Light Element ◽  
Big Bang ◽  
Microwave Background ◽  
Dark Matter Annihilation ◽  
Element Abundances ◽  
Primordial Plasma ◽  
Relic Abundance ◽  
The Universe

The astronomical dark matter is an essential component of the Universe and yet its nature is still unresolved. It could be made of neutral and massive elementary particles which are their own antimatter partners. These dark matter species undergo mutual annihilations whose effects are briefly reviewed in this article. Dark matter annihilation plays a key role at early times as it sets the relic abundance of the particles once they have decoupled from the primordial plasma. A weak annihilation cross section naturally leads to a cosmological abundance in agreement with observations. Dark matter species subsequently annihilate — or decay — during Big Bang nucleosynthesis and could play havoc with the light element abundances unless they offer a possible solution to the 7 Li problem. They could also reionize the intergalactic medium after recombination and leave visible imprints in the cosmic microwave background. But one of the most exciting aspects of the question lies in the possibility to indirectly detect the dark matter species through the rare antimatter particles — antiprotons, positrons and antideuterons — which they produce as they currently annihilate inside the galactic halo. Finally, the effects of dark matter annihilation on stars is discussed.

scholarly journals Hidden sector monopole dark matter with matter domination

2020 ◽  
Vol 2020 (11) ◽  
Author(s):  
Michael L. Graesser ◽  
Jacek K. Osiński
Keyword(s):  
Dark Matter ◽  
Cross Sections ◽  
Particle Physics ◽  
Magnetic Monopoles ◽  
Number Density ◽  
Pure Radiation ◽  
Hidden Sector ◽  
Equilibrium Dynamics ◽  
Thermal Histories ◽  
Relic Abundance

Abstract The thermal freeze-out mechanism for relic dark matter heavier than O(10 − 100 TeV) requires cross-sections that violate perturbative unitarity. Yet the existence of dark matter heavier than these scales is certainly plausible from a particle physics perspective, pointing to the need for a non-thermal cosmological history for such theories. Topological dark matter is a well-motivated scenario of this kind. Here the hidden-sector dark matter can be produced in abundance through the Kibble-Zurek mechanism describing the non-equilibrium dynamics of defects produced in a second order phase transition. We revisit the original topological dark matter scenario, focusing on hidden-sector magnetic monopoles, and consider more general cosmological histories. We find that a monopole mass of order (1–105) PeV is generic for the thermal histories considered here, if monopoles are to entirely reproduce the current abundance of dark matter. In particular, in a scenario involving an early era of matter domination, the monopole number density is always less than or equal to that in a pure radiation dominated equivalent provided a certain condition on critical exponents is satisfied. This results in a larger monopole mass needed to account for a fixed relic abundance in such cosmologies.

scholarly journals Lepton dark matter portal in the inert Zee model

2020 ◽  
Vol 35 (31) ◽  
pp. 2050190
Author(s):  
Alexandra Gaviria ◽  
Robinson Longas ◽  
Andrés Rivera
Keyword(s):  
Dark Matter ◽  
Parameter Space ◽  
Tree Level ◽  
Neutrino Masses ◽  
Dark Matter Annihilation ◽  
Annihilation Channel ◽  
Flavor Changing ◽  
Inert Doublet Model ◽  
Relic Abundance ◽  
The Impact

The inert Zee model is an extension of the Zee model for neutrino masses. This new model explains the dark matter relic abundance, generates a one-loop neutrino masses and forbids tree-level Higgs-mediated flavor changing neutral currents. Although the dark matter phenomenology of the model is similar to that of the inert doublet model, the presence of new vector-like fermions opens the lepton portal as a new dark matter annihilation channel. We study the impact of this new portal in the low-mass regime and show the parameter space allowed by direct and indirect searches of dark matter. Remarkably, the region for [Formula: see text] GeV is recovered for [Formula: see text]. We also show that future experiments like LZ and DARWIN could probe a large region of the parameter space of the model.

scholarly journals When freeze-out occurs due to a non-Boltzmann suppression: a study of degenerate dark sector

2021 ◽  
Vol 2021 (6) ◽  
Author(s):  
Anirban Biswas ◽  
Sougata Ganguly ◽  
Sourov Roy
Keyword(s):  
Dark Matter ◽  
Direct Detection ◽  
Atmospheric Neutrino ◽  
Radioactive Decay ◽  
Number Density ◽  
Dark Sector ◽  
Dark Matter Annihilation ◽  
Cascade Processes ◽  
Chemical Imbalance ◽  
Freeze Out

Abstract Exponential suppression or commonly known as the Boltzmann suppression in the number density of dark matter is the key ingredient for creating chemical imbalance prior to the usual thermal freeze-out. A degenerate/quasi-degenerate dark sector can experience a different exponential suppression in the number density analogous to the radioactive decay law leading to a delayed freeze-out mechanism of dark matter known as the co-decaying dark matter. In this work, we study the dynamics of a multicomponent dark matter from thermally decoupled degenerate dark sector in a hidden U(1)X extension of the Standard Model. We compute the relic density of dark matter frozen-out through the co-decaying mechanism by solving four coupled Boltzmann equations. We demonstrate how temperature T′ of the dark sector changes due to all types of 3 → 2 and 2 → 2 interactions along with the eternal expansion of the Universe. We find that 3 → 2 interactions enhance T′ by producing energetic particles in the dark sector while the excess heat is transferred by 2 → 2 interactions to the entire dark sector. As the direct detection is possible only through the feeble portal couplings, we investigate the neutrino and γ-ray signals from dark matter annihilation via one step cascade processes and compare our results with the measured fluxes of atmospheric neutrinos by Super-Kamiokande and diffuse γ-rays by Fermi-LAT, EGRET, INTEGRAL collaborations. We find that the present scenario easily evades all the existing bounds from atmospheric neutrino and diffuse γ-ray observations for degenerate dark sector. However, the constraints are significant for quasi degenerate scenario.

scholarly journals Asymmetric dark matter and the scalar-tensor model

2016 ◽  
Vol 31 (07) ◽  
pp. 1650021 ◽  
Author(s):  
Shun-Zhi Wang ◽  
Hoernisa Iminniyaz ◽  
Mamatrishat Mamat
Keyword(s):  
Dark Matter ◽  
Parameter Space ◽  
Expansion Rate ◽  
Tensor Model ◽  
Hubble Expansion ◽  
Cosmological Scenario ◽  
Relic Density ◽  
Asymmetric Dark Matter ◽  
Relic Abundance

The relic abundance of asymmetric dark matter particles in the scalar-tensor model is analyzed in this paper. We extend the numerical and analytical calculations of the relic density of the asymmetric dark matter in the standard cosmological scenario to the nonstandard cosmological scenario. We focus on the scalar-tensor model. Hubble expansion rate is changed in the nonstandard cosmological scenario. This leaves its imprint on the relic density of dark matter particles. In this paper we investigate to what extent the asymmetric dark matter particle’s relic density is changed in the scalar-tensor model. We use the observed present day dark matter abundance to find the constraints on the parameter space in this model.

scholarly journals 2HDM singlet portal to dark matter

2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
M. E. Cabrera ◽  
J. A. Casas ◽  
A. Delgado ◽  
S. Robles
Keyword(s):  
Dark Matter ◽  
Cross Section ◽  
Parameter Space ◽  
Direct Detection ◽  
Single Parameter ◽  
Relic Density ◽  
Relic Abundance ◽  
Higgs Portal ◽  
The Universe

Abstract Higgs portal models are the most minimal way to explain the relic abundance of the Universe. They add just a singlet that only couples to the Higgs through a single parameter that controls both the dark matter relic abundance and the direct detection cross-section. Unfortunately this scenario, either with scalar or fermionic dark matter, is almost ruled out by the latter. In this paper we analyze the Higgs-portal idea with fermionic dark matter in the context of a 2HDM. By disentangling the couplings responsible for the correct relic density from those that control the direct detection cross section we are able to open the parameter space and find wide regions consistent with both the observed relic density and all the current bounds.

Radiation exposure in the environment of patients after application of radiopharmaceuticals

2008 ◽  
Vol 47 (06) ◽  
pp. 267-274 ◽  
Author(s):  
F. Boldt ◽  
C. Kobe ◽  
W. Eschner ◽  
H. Schicha ◽  
F. Sudbrock
Keyword(s):  
Nuclear Medicine ◽  
Radiation Exposure ◽  
Radioactive Source ◽  
Time Intervals ◽  
The Public ◽  
Dose Rates ◽  
Diagnostic Nuclear Medicine ◽  
Photon Dose ◽  
Order Of Magnitude ◽  
Study Dose

Summary Aim: After application of radiopharmaceuticals the patient becomes a radioactive source which leads to radiation exposure in the proximity. The photon dose rates after administration of different radiopharmaceuticals used in diagnostic nuclear medicine were measured at several distances and different time intervals. These data are of importance for estimating the exposure of technologists and members of the public. Patients, method: In this study dose rates were measured for 67 patients after application of the following radiopharmaceuticals: 99mTc-HDP as well as 99mTcpertechnetate, 18F-fluorodeoxyglucose, 111In-Octreotid and Zevalin® and 123I-mIBG in addition to 123I-NaI. The dose rates were measured immediately following application at six different distances to the patient. After two hours the measurements were repeated and – whenever possible – after 24 hours and seven days. Results: Immediately following application the highest dose rates were below 1 mSv / h: with a maximum at 780 μSv/h for 18F (370 MBq), 250 μSv/h for 99mTc (700 MBq), 150 μSv/h for 111In (185 MBq) and 132 μSv/ h for 123I (370 MBq). At a distance of 0.5 m the values decrease significantly by an order of magnitude. Two hours after application the values are diminished to 1/3 (99mTc, 18F), to nearly ½ (123I) but remain in the same order of magnitude for the longer-lived 111In radiopharmaceuticals. Conclusion: For greater distances the doses remain below the limits outlined in the national legislation.

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