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Refinement of the standard halo model for dark matter searches in light of the Gaia Sausage

Research output: Contribution to journalArticlepeer-review

Wyn Evans, Ciaran O'Hare, Christopher McCabe

Original languageEnglish
Article number023013
Pages (from-to)023012
JournalPhysical Review D - Particles, Fields, Gravitation and Cosmology
Volume99
Issue number2
DOIs
Published15 Jan 2019

Documents

  • PhysRevD.99.023012

    PhysRevD.99.023012.pdf, 1.41 MB, application/pdf

    Uploaded date:07 Feb 2019

King's Authors

Abstract

Predicting signals in experiments to directly detect dark matter (DM) requires a form for the local DM velocity distribution. Hitherto, the standard halo model (SHM), in which velocities are isotropic and follow a truncated Gaussian law, has performed this job. New data, however, suggest that a substantial fraction of our stellar halo lies in a strongly radially anisotropic population, the “Gaia sausage.” Inspired by this recent discovery, we introduce an updated DM halo model, the
SHM++, which includes a “sausage” component, thus better describing the known features of our Galaxy. The SHM++ is a simple analytic model with five parameters: the circular speed, local escape speed, and local DM density, which we update to be consistent with the latest data, and two new parameters: the anisotropy and the density of DM in the sausage. The impact of the SHM++ on signal models for weakly interacting massive particles (WIMPs) and axions is rather modest since the multiple changes and updates have competing effects. In particular, this means that the older exclusion limits derived for WIMPS are still reasonably accurate. However, changes do occur for directional detectors, which have sensitivity to the full three-dimensional velocity distribution.

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