A Dark Matter Solution from the Supersymmetric Axion Model

Abstract

We study the effect of the late decaying saxino (the scalar superpartner of the axion) and find out that there is a possible dark matter solution from a class of supersymmetric extensions of the invisible axion model. In this class of models, the saxino which decays into two axions acts as the late decaying . If we stick to the theoretical prejudice, Ω 0 = 1, we have at least two serious problems. First, we cannot fit the power spectrum curve even in the MDM model. Second, it would be inconsistent with the estimated lower bound on the age of the universe from the oldest globular clusters. An Ω 0 = 1 universe has an age of only t 0 = 6.5h −1 Gyr, giving t 0 < 9.3 Gyr for h > 0.7. On the other hand, the observed value of the age of the oldest globular cluster is around 15 Gyr [4]. Still there are a few possible way to relax this bound, but it seems not to be less than 11 Gyr [5]. Assuming that the data from the globular cluster can be relaxed by some mechanism and considering error bars in Hubble constant observations, h = 0.6 would be marginally allowed. However, the standard MDM model is inconsistent with large scale structure data even for h = 0.6.

Hadronic axion model in gauge-mediated supersymmetry breaking and the cosmology of the saxion

“…In this section, we would like to argue that this feature of the saxion particle could explain well the present observed power spectrum of the cosmic structure with some cold dark matter [22], i.e., the saxion can be a candidate for a late decaying massive particle (LDP) [23,24].…”

Dark-matter candidates

“…(ii) Late decays of the saxion can lead to significant entropy production [365][366][367][368] and can thereby affect the cosmological constraints [369]. In this review, however, a standard thermal history is assumed which implies that saxion effects are negligible.…”

Quintessential kination and thermal production of gravitinos and axinos

“…The production ofã is usually accompanied by the production of a scalar SUSY partner, the s-axion; this may undergo out-ofequilibrium decays [59], producing entropy and therefore, diluting any prexisting Ωãh 2 . In our analysis, we assume that this is not the case [26].…”