Gravitino or axino dark matter with reheat temperature as high as 1016 GeV

Abstract

A new scheme for lightest supersymmetric particle (LSP) dark matter is introduced and studied in theories of TeV supersymmetry with a QCD axion, a, and a high reheat temperature after inflation, TR. A large overproduction of axinos (ã) and gravitinos left(tilde{G}right) from scattering at TR, and from freeze-in at the TeV scale, is diluted by the late decay of a saxion condensate that arises from inflation. The two lightest superpartners are ã, with mass of order the TeV scale, and tilde{G} with mass m3/2 anywhere between the keV and TeV scales, depending on the mediation scale of supersymmetry breaking. Dark matter contains both warm and cold components: for tilde{G} LSP the warm component arises from tilde{a}to tilde{G}a , while for ã LSP the warm component arises from tilde{G}to tilde{a}a . The free-streaming scale for the warm component is predicted to be of order 1 Mpc (and independent of m3/2 in the case of tilde{G} LSP). TR can be as high as 1016 GeV, for any value of m3/2, solving the gravitino problem. The PQ symmetry breaking scale VPQ depends on TR and m3/2 and can be anywhere in the range (1010 − 1016) GeV. Detailed predictions are made for the lifetime of the neutralino LOSP decaying to ã+h/Z and tilde{G}+h/Z/gamma , which is in the range of (10−1 −106)m over much of parameter space. For an axion misalignment angle of order unity, the axion contribution to dark matter is sub-dominant, except when VPQ approaches 1016 GeV.