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Cosmological mass limits on neutrinos, axions, and other light particles

Steen Hannestad1 and Georg Raffelt2

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The small-scale power spectrum of the cosmological matter distribution, together with other cosmological data, provides a sensitive measure of the hot dark matter fraction, leading to restrictive neutrino mass limits. We extend this argument to generic cases of low-mass thermal relics. We vary the cosmic epoch of thermal decoupling, the radiation content of the universe, and the new particle's spin degrees of freedom. Our treatment covers various scenarios of active plus sterile neutrinos or axion-like particles. For three degenerate massive neutrinos, we reproduce the well-known limit of mν<0.34 eV. In a 3+1 scenario of 3 massless and 1 fully thermalized sterile neutrinos we find mν<1.0 eV. Thermally produced QCD axions must obey ma<3.0 eV, superseding limits from a direct telescope search, but leaving room for solar eV-mass axions to be discovered by the CAST experiment.


Keywords

dark matter

axions

cosmological neutrinos

 

E-print Number: hep-ph/0312154

Cited: by |

Refers: to

PACS

98.80.-k Cosmology

14.60.Pq Neutrino mass and mixing

95.85.Ry Neutrino, muon, pion, and other elementary particles; cosmic rays

96.50.S- Cosmic rays

14.80.Mz Axions and other Nambu-Goldstone bosons (Majorons, familons, etc.)

95.35.+d Dark matter (stellar, interstellar, galactic, and cosmological)

Subjects

Gravitation and cosmology

Particle physics and field theory

Astrophysics and astroparticles

Dates

Issue 04 (April 2004)

Received 3 February 2004, accepted for publication 14 April 2004

Published 29 April 2004



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