Light dark matter and dark radiation

Jae Ho Heo, C. S. Kim

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Light (M ≤ 20 MeV) dark-matter particles freeze out after neutrino decoupling. If the dark-matter particle couples to a neutrino or an electromagnetic plasma, the late time entropy production from dark-matter annihilation can change the neutrino-to-photon temperature ratio, and equally the effective number of neutrinos Neff. We study the non-equilibrium effects of dark-matter annihilation on the Neff and the effects by using a thermal equilibrium approximation. Both results are constrained with Planck observations. We demonstrate that the lower bounds of the dark-matter mass and the possibilities of the existence of additional radiation particles are more strongly constrained for dark-matter annihilation process in non-equilibrium.

Original languageEnglish
Pages (from-to)715-721
Number of pages7
JournalJournal of the Korean Physical Society
Volume68
Issue number5
DOIs
Publication statusPublished - 2016 Mar 1

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dark matter
radiation
neutrinos
temperature ratio
decoupling
entropy
electromagnetism
photons
approximation

All Science Journal Classification (ASJC) codes

  • Physics and Astronomy(all)

Cite this

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Light dark matter and dark radiation. / Heo, Jae Ho; Kim, C. S.

In: Journal of the Korean Physical Society, Vol. 68, No. 5, 01.03.2016, p. 715-721.

Research output: Contribution to journalArticle

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AU - Kim, C. S.

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AB - Light (M ≤ 20 MeV) dark-matter particles freeze out after neutrino decoupling. If the dark-matter particle couples to a neutrino or an electromagnetic plasma, the late time entropy production from dark-matter annihilation can change the neutrino-to-photon temperature ratio, and equally the effective number of neutrinos Neff. We study the non-equilibrium effects of dark-matter annihilation on the Neff and the effects by using a thermal equilibrium approximation. Both results are constrained with Planck observations. We demonstrate that the lower bounds of the dark-matter mass and the possibilities of the existence of additional radiation particles are more strongly constrained for dark-matter annihilation process in non-equilibrium.

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