We will consider a SUSY-SU(5) with one right-handed neutrino with a large top
like Yukawa coupling. Assuming universal soft masses at high scale we compute
the low-energy spectrum and subsequently the neutralino LSP relic density
taking also into consideration SU(5) as well as the see-saw running effects
above the gauge coupling unification scale. We found that there exists no
viable region in parameter space for \tan\beta \ler ~35. The τ~
coannihilation process starts becoming efficient for \tan\beta \ger 35-40.
However, this process is significantly constrained by the limited range in
which the stau is lighter than the neutralino. In fact, for a given tanβ
we find that there exists an upper bound on the lightest neutralino mass
(Mχ10) in this region. The A-pole funnel region appears at very large
tanβ≃45−50, while the focus-point region does not make an
appearance till large (m0,M1/2), namely a few TeV. Large A0 terms at
high scale can lead to extended regions consistent with WMAP constraints and
remove the upper bounds in the stau coannihilation regions.Comment: 18 pages, 7 figures; references added, figure added, improved
discussions in text, to appear in JHE