Ruling out the light weakly interacting massive particle explanation of the Galactic 511 keV line

Ryan J. Wilkinson, Aaron C. Vincent, Céline Bœhm, and Christopher McCabe
Phys. Rev. D 94, 103525 – Published 28 November 2016

Abstract

Over the past few decades, an anomalous 511 keV gamma-ray line has been observed from the center of the Milky Way. Dark matter (DM) in the form of light (10MeV) weakly interacting massive particles (WIMPs) annihilating into electron-positron pairs has been one of the leading hypotheses of the observed emission. Given the small required cross section, σv1030cm3s1, a further coupling to lighter particles is required to produce the correct relic density. Here, we derive constraints from the Planck satellite on light WIMPs that were in equilibrium with either the neutrino or electron sector in the early universe. For the neutrino sector, we obtain a lower bound on the WIMP mass of 4 MeV for a real scalar and 10 MeV for a Dirac fermion DM particle, at 95% C.L. For the electron sector, we find even stronger bounds of 7 and 11 MeV, respectively. Using these results, we show that, in the absence of additional ingredients such as dark radiation, the light thermally produced WIMP explanation of the 511 keV excess is strongly disfavored by the latest cosmological data. This suggests an unknown astrophysical or more exotic DM source of the signal.

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  • Received 10 February 2016

DOI:https://doi.org/10.1103/PhysRevD.94.103525

© 2016 American Physical Society

Physics Subject Headings (PhySH)

Gravitation, Cosmology & AstrophysicsParticles & Fields

Authors & Affiliations

Ryan J. Wilkinson1, Aaron C. Vincent1,4, Céline Bœhm1,2, and Christopher McCabe3

  • 1Institute for Particle Physics Phenomenology (IPPP), Durham University, Durham DH1 3LE, United Kingdom
  • 2LAPTH, Université. de Savoie, CNRS, BP 110, 74941 Annecy-Le-Vieux, France
  • 3GRAPPA Centre of Excellence, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, Netherlands
  • 4Department of Physics, Blackett Laboratory, Imperial College London, SW7 2AZ, London

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Issue

Vol. 94, Iss. 10 — 15 November 2016

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