New cosmological mass limit on thermal relic axions
نویسندگان
چکیده
Observations of the cosmological large-scale structure provide wellestablished neutrino mass limits. We extend this argument to thermal relic axions. We calculate the axion thermal freeze-out temperature and thus their cosmological abundance on the basis of their interaction with pions. For hadronic axions we find a new mass limit ma < 1.05 eV (95% CL), corresponding to a limit on the axion decay constant of fa > 5.7× 10 6 GeV. For other models this constraint is significantly weakened only if the axion-pion coupling is strongly suppressed. For comparison we note that the same approach leads to ∑ mν < 0.65 eV (95% CL) for neutrinos. New cosmological mass limit on thermal relic axions 2
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