Besides, with gaugino universality at the GUT scale, it is a struggle to fully accommodate the measured value of the Higgs mass at the LHC [47, 51] (this problem is resolved if the gluino mass is a free parameter, e.g., ).
However, the rapid progress made in the bounds on the spin-independent cross section of the neutralino scattering off nuclei in direct WIMP detection searches, combined with a failure to directly observe scalar fermions and heavy Higgs bosons at the LHC, have rendered scenarios where the lightest neutralino is a rich admixture of gaugino and higgsino much less appealing if not excluded altogether (see, e.g.
To briefly set the issue on quantitative grounds, let us estimate the strength of the coupling with which neutralino admixtures of higgsino and gaugino contribute to the spin-independent cross section.
We begin in Figure 4(a), where we plot the rescaled spin-independent neutralino-nucleon cross section versus neutralino mass for a nearly pure higgsino under CMSSM/mSUGRA boundary conditions  (We remind the reader that this means scanning simultaneously over 4 free parameters: [m.sub.0], the universal soft SUSY-breaking scalar mass at the GUT scale; [m.sub.1/2], the universal GUT-scale gaugino mass; [A.sub.0], the universal GUT-scale soft trilinear coupling; and tan [beta], the ratio of the Higgs doublets' vevs.
Murayama, "Gaugino mass without singlets," Journal of High Energy Physics, vol.
Two of these particles are gauginos, fermionic superpartners of the SM gauge bosons.
A way to evade the strong collider bounds is provided, if the bino-like neutralino and some other sparticles (sfermions [??] or other gauginos) are nearly degenerate in mass, by the mechanism of coannihilation [43-45].
Of course, expressions similar to (5)-(6) can give us a lower bound on the scale of the electroweak gauginos for every given upcoming new constraint on [[sigma].sup.SI.sub.p], but to be precise one should then take into account the rich parametric dependence of the full formulas.
Abajyan et al., "Search for direct slepton and gaugino
production in final states with two leptons and missing transverse momentum with the ATLAS detector in pp collisions at [square root of s] = 7 TeV," Physics Letters B, vol.