Dark-matter harmonics beyond annual modulation

Samuel K. Lee, Mariangela Lisanti, Benjamin R. Safdi

Research output: Contribution to journalArticle

41 Scopus citations

Abstract

The count rate at dark-matter direct-detection experiments should modulate annually due to the motion of the Earth around the Sun. We show that higher-frequency modulations, including daily modulation, are also present and in some cases are nearly as strong as the annual modulation. These higher-order modes are particularly relevant if (i) the dark matter is light, O(10) GeV, (ii) the scattering is inelastic, or (iii) velocity substructure is present; for these cases, the higher-frequency modes are potentially observable at current and ton-scale detectors. We derive simple expressions for the harmonic modes as functions of the astrophysical and geophysical parameters describing the Earth's orbit, using an updated expression for the Earth's velocity that corrects a common error in the literature. For an isotropic halo velocity distribution, certain ratios of the modes are approximately constant as a function of nuclear recoil energy. Anisotropic distributions can also leave observable features in the harmonic spectrum. Consequently, the higher-order harmonic modes are a powerful tool for identifying a potential signal from interactions with the Galactic dark-matter halo.

Original languageEnglish (US)
Article number033
JournalJournal of Cosmology and Astroparticle Physics
Volume2013
Issue number11
DOIs
StatePublished - Nov 1 2013

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics

Keywords

  • dark matter detectors
  • dark matter experiments
  • dark matter theory

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