paper

Coupled Boltzmann computation of mixed axion neutralino dark matter in the SUSY DFSZ axion model

arXiv:1406.4138 · doi:10.1088/1475-7516/2014/10/082

Abstract

The supersymmetrized DFSZ axion model is highly motivated not only because it offers solutions to both the gauge hierarchy and strong CP problems, but also because it provides a solution to the SUSY mu problem which naturally allows for a Little Hierarchy. We compute the expected mixed axion-neutralino dark matter abundance for the SUSY DFSZ axion model in two benchmark cases-- a natural SUSY model with a standard neutralino underabundance (SUA) and an mSUGRA/CMSSM model with a standard overabundance (SOA). Our computation implements coupled Boltzmann equations which track the radiation density along with neutralino, axion (produced thermally (TH) and via coherent oscillations (CO)), saxion (TH- and CO-produced), axino and gravitino densities. In the SUSY DFSZ model, axions, axinos and saxions go through the process of freeze-in-- in contrast to freeze-out or out-of-equilibrium production as in the SUSY KSVZ model-- resulting in thermal yields which are largely independent of the re-heat temperature. We find the SUA case with suppressed saxion-axion couplings (ξ=0) only admits solutions for PQ breaking scale f_a~< 5\times 10^{12} GeV where the bulk of parameter space tends to be axion-dominated. For SUA with allowed saxion-axion couplings (ξ=1), then f_a values up to ~ 2\times 10^{14} GeV are allowed. For the SOA case, almost all of SUSY DFSZ parameter space is disallowed by a combination of overproduction of dark matter, overproduction of dark radiation or violation of BBN constraints. An exception occurs at very large f_a~ 10^{15}-10^{16} GeV where large entropy dilution from CO-produced saxions leads to allowed models.

arXiv comment24 pages plus 12 figures; final ArXiv version contains admx reach plot

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