2013/01/31 by Kyu Jung Bae, Howard Baer, André Lessa +1
Physics and Astronomy · #Astrophysics #Axion #CMB cold spot #Cold dark matter #Cosmic microwave background #Cosmology #Cosmology and Gravitation Theories #Dark Matter and Cosmic Phenomena #Dark energy #Dark matter #Dark radiation #Hot dark matter #Neutralino #Particle physics #Particle physics theoretical and experimental studies #Physics #Quantum mechanics #R-parity #Strong CP problem #Supersymmetry #Warm dark matter #astro-ph.CO #astro-ph.HE #hep-ph
paper · pdf · doi:10.1088/1475-7516/2013/04/041
Version 2 is updated to reflect revised WMAP9 data and also recent ACT and SPT data on dark radiation; 35 pages with 12 .eps figures
arxiv created 2013/02/19 · openalex publication_date 2013/04/29 · arxiv updated 2015/06/12 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
Recent analyses of CMB data combined with the measurement of BAO and H 0 show that dark radiation — parametrized by the apparent number of additional neutrinos Δ N eff contributing to the cosmic expansion — is bounded from above by about Δ N eff ≲1.6 at 95% CL. We consider the mixed axion/neutralino cold dark matter scenario which arises in R -parity conserving supersymmetric (SUSY) models wherein the strong CP problem is solved by hadronic axions with a concommitant axion( a )/saxion( s )/axino(ã) supermultiplet. Our new results include improved calculations of thermal axion and saxion production and include effects of saxion decay to axinos and axions. We show that the above bound on Δ N eff is easily satisfied if saxions are mainly thermally produced and m LSP < m ã ≲ m s . However, if the dominant mechanism of saxion production is through coherent oscillations, the CMB data provides a strong bound on saxion production followed by saxion decays to axions. Furthermore we show that scenarios with mixed neutralino/axion dark matter are highly constrained by combined CMB, BBN and Xe-100 constraints. In particular, supersymmetric models with a standard overabundance of neutralino dark matter are excluded for all values of the Peccei-Quinn breaking scale . Next generation WIMP direct detection experiments may be able to discover or exclude mixed axion-neutralino CDM scenarios where s → aa is the dominant saxion decay mode.