Corrections to bino annihilation. I. Sfermion mixing

Abstract

We consider corrections to bino annihilation due to sfermion mixing.

Phases in the MSSM, electric dipole moments and cosmological dark matter

“…(This upper limit is somewhat dependent on the value of of the top quark mass. In [7,9], we found that the upper limit was ∼ 250 GeV for m t ∼ 100 GeV. When m t = 174 GeV, the upper limit is 260 GeV.…”

“…As the bino mass is increased, there is an upper limit m B < ∼ 250 GeV [7,8]. In [9], it was shown that this upper limit is sensitive to the level of sfermion mixing. Here, we find that the upper limit to the bino mass is relaxed when phases in the MSSM, and in particular the phases associated with the off-diagonal sfermion masses, are allowed to take non-zero values.…”

“…Previously [9] we considered the effect of sfermion mixing on the relic density when the neutralino is mostly gaugino, and in particular a bino. The LSP is a bino whenever M 2 < µ and M 2 > ∼ 200 GeV; for smaller M 2 , the bino is still the LSP for large enough values of µ.…”

“…Note that this provides an upper bound on the sfermion masses as well, since the mass of the lightest sfermion is equal to the mass of the bino, when the bino mass takes its maximum value. When sfermion mixing is included [9], the limits, which now depend on the magnitude of the off-diagonal elements m f m f , are modified. We find that this upper limit is relaxed considerably when the phases are allowed to take non-zero values.…”

“…Then for several values of m t between 0 and 1500 GeV, we determine the upper bound on m B , as a function of θ µ . As we vary θ µ across its full range, m b and γ t change, and this affects the annihilation rate (see (9) and following discussion), and consequently the bound on m B . Taking m B at its maximum value allows us to take M 2 L as large as possible; although the electric dipole moments depend on m B as well, we find that the dependence on M 2 L is sufficiently strong that the EDM's take their minimum values for the maximum values of m B and M 2 L .…”