How Dark is ‘Dark’? Electromagnetic Interactions in the Dark Sector

Sigurdson, Kris

doi:10.1007/3-540-26373-x_33

Cited by 13 publications

(26 citation statements)

References 33 publications

(39 reference statements)

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“…As discussed in, for example, Refs. [8,10], in a universe with both a visible and hidden sector there are two copies of these functions, g v (T ) for the visible sector and g h (T h ) for the hidden sector. Since for relativistic particles the energy density scales as ρ ∝ T 4 and entropy density scales as s ∝ T 3 we find that the combined g(T ) and g s (T ) take the form…”

Section: The Relic Abundancementioning

confidence: 99%

“…Generally, hidden-sector dark matter does not need to freeze-out when nonrelativistic (cold) in order to match observations [10]. The dark-matter particles may have significant thermal momentum at freeze-out (it can be warm or hot from the hidden-sector perspective), and this can lead to a significant free-streaming length that can suppress the matter power spectrum on scales as large as those corresponding to galactic length scales.…”

Section: Bound From Free-streamingmentioning

confidence: 99%

“…Here, a nr corresponds to a scale factor when dark matter particles becomes nonrelativistic (T h nr m χ /3.15) [10]. This corresponds to a visible sector temperature T nr (m χ /(3.15ξ))(g s f /g s nr ) 1/3 .…”

Section: Bound From Free-streamingmentioning

confidence: 99%

“…In all cases the comoving free-streaming length must satisfy the bound from the measurements of the linear power spectra on small scales which in turn constrains the dark-matter parameter space (ξ, σ, m χ ). We use here the bound λ F SH ≤ 230 kpc [10,26].…”

Section: Bound From Free-streamingmentioning

confidence: 99%

“…In Ref. [10] hidden-sector models that decoupled when ultrarelativistic were considered. In this work we present a unified treatment of the freeze-out of thermal relics in hidden sectors for arbitrary cross section σ, only requiring that constraints from cosmology are satisfied, and find viable dark matter that freezes out when it is relativistic, semirelativistic, or nonrelativistic.…”

Section: Introductionmentioning

confidence: 99%

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Cosmological limits on hidden sector dark matter

Das

Sigurdson

2012

Phys. Rev. D

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We explore the model-independent constraints from cosmology on a dark-matter particle with no prominent standard model interactions that interacts and thermalizes with other particles in a hidden sector. Without specifying detailed hidden-sector particle physics, we characterize the relevant physics by the annihilation cross section, mass, and temperature ratio of the hidden to visible sectors. While encompassing the standard cold WIMP scenario, we do not require the freezeout process to be nonrelativistic. Rather, freeze-out may also occur when dark matter particles are semirelativistic or relativistic. We solve the Boltzmann equation to find the conditions that hidden-sector dark matter accounts for the observed dark-matter density, satisfies the TremaineGunn bound on dark-matter phase space density, and has a free-streaming length consistent with cosmological constraints on the matter power spectrum. We show that for masses 1.5 keV no region of parameter space satisfies all these constraints. This is a gravitationally-mediated lower bound on the dark-matter mass for any model in which the primary component of daqrk matter once had efficient interactions -even if it has never been in equilibrium with the standard model.

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Section: The Relic Abundancementioning

confidence: 99%

Section: Bound From Free-streamingmentioning

confidence: 99%

Section: Bound From Free-streamingmentioning

confidence: 99%

Section: Bound From Free-streamingmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Cosmological limits on hidden sector dark matter

Das

Sigurdson

2012

Phys. Rev. D

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First light and reionization: A conference summary

Barton

Bullock

Cooray

et al. 2006

New Astronomy Reviews

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The search for the first illuminated astronomical sources in the universe is at the edge of the cosmic frontier. Promising techniques for discovering the first objects and their effects span the electromagnetic spectrum and include gravitational waves. We summarize a workshop on discovering and understanding these sources which was held in May 2005 through the Center for Cosmology at the University of California, Irvine.

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PeV-scale dark matter as a thermal relic of a decoupled sector

2016

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In this letter, we consider a class of scenarios in which the dark matter is part of a heavy hidden sector that is thermally decoupled from the Standard Model in the early universe. The dark matter freezes-out by annihilating to a lighter, metastable state, whose subsequent abundance can naturally come to dominate the energy density of the universe. When this state decays, it reheats the visible sector and dilutes all relic abundances, thereby allowing the dark matter to be orders of magnitude heavier than the weak scale. For concreteness, we consider a simple realization with a Dirac fermion dark matter candidate coupled to a massive gauge boson that decays to the Standard Model through its kinetic mixing with hypercharge. We identify viable parameter space in which the dark matter can be as heavy as ∼1-100 PeV without being overproduced in the early universe.The Weakly Interacting Massive Particle (WIMP) paradigm provides a compelling cosmological origin for dark matter (DM) candidates with weak-scale masses and interactions. In the early universe, at temperatures above the WIMP's mass, interactions with the Standard Model (SM) produce a thermal population of WIMPs and sustain chemical equilibrium between dark and visible matter. When the temperature falls below the WIMP's mass, these interactions freeze-out to yield an abundance similar to the observed cosmological DM density. This narrative is known as the "WIMP miracle."In recent years, however, this framework has become increasingly constrained. The Large Hadron Collider has not yet discovered any new physics, and limits from direct detection experiments have improved at an exponential rate over the past decade. For DM candidates that annihilate at a sufficient rate to avoid being overproduced in the early universe, unacceptably large elastic scattering cross sections with nuclei are often predicted. To evade these constraints, one is forced to consider models that include features such as coannihilations [1,2], resonant annihilations [1,3], pseudoscalar couplings [4][5][6][7], or annihilations to final states consisting of leptons or electroweak bosons [8][9][10][11][12][13][14][15][16].It is equally plausible, however, that the DM is a singlet under the SM and was produced independently of the visible sector during the period of reheating that followed inflation (for a review, see Ref.[17]). By freezingout through annihilations to SM singlets, the DM in such models can avoid being overproduced while easily evading the constraints from direct detection experiments [18][19][20][21][22][23][24][25]. In this letter, we explore this class of scenarios, focusing on hidden sectors that are thermally decoupled and, therefore, never reach equilibrium with the visible sector. In this case, the DM freezes-out of chemical equilibrium within its own sector, unaffected by SM dynamics.So long as the hidden sector consists entirely of SM singlets, renormalizable interactions between the SM and the DM can proceed only through the following gauge singlet operators: H † H, ...

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How Dark is ‘Dark’? Electromagnetic Interactions in the Dark Sector

Cited by 13 publications

References 33 publications

Cosmological limits on hidden sector dark matter

Cosmological limits on hidden sector dark matter

First light and reionization: A conference summary

PeV-scale dark matter as a thermal relic of a decoupled sector

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