Abstract:When the GUT relation on gaugino masses is relaxed, the mass and composition of the lightest neutralino are different from those in the GUT case. We discuss its phenomenological implications on the relic abundance of the neutralinos and on superparticle searches. In particular, we focus on the case where the neutral component of Winos dominates the lightest neutralino. It turns out the Wino-LSP is not a candidate for the dark matter. where g i (i =1, 2, 3) are the gauge coupling constants of the gauge groups (… Show more
“…The flipped SU (5) is another example where the non-universality of the gaugino masses naturally arises [25]. The gauge group is SU(5) × U(1) and thus even if the SU(5) part gives a universal contribution the gaugino mass from U(1) in general gives a different mass, violating the universality of the U(1) Y gaugino mass with the rest two.…”
Section: A Examples Of Non-universal Gaugino Massesmentioning
Phenomenological issues of no-scale structure of Kähler potential are reexamined, which arises in various approaches to supersymmetry breaking.When no-scale boundary conditions are given at the Grand Unified scale and universal gaugino masses are postulated, a bino mass is quite degenerate with right-handed slepton masses and the requirement that the lightest superparticle (LSP) be neutral supplemented with slepton searches at LEP200 severely constrains allowed mass regions of superparticles. The situation drastically changes if one moderately relaxes the assumption of the universal gaugino masses. After reviewing some interesting scenarios where non-universal gaugino masses arise, we show that the non-universality diminishes the otherwise severe constraint on the superparticle masses, and leads a variety of superparticle mass spectra: in particular the LSP can be a wino-like neutralino, a higgsino-like neutralino, or even a sneutrino, and also left-handed sleptons can be lighter than right-handed ones.
“…The flipped SU (5) is another example where the non-universality of the gaugino masses naturally arises [25]. The gauge group is SU(5) × U(1) and thus even if the SU(5) part gives a universal contribution the gaugino mass from U(1) in general gives a different mass, violating the universality of the U(1) Y gaugino mass with the rest two.…”
Section: A Examples Of Non-universal Gaugino Massesmentioning
Phenomenological issues of no-scale structure of Kähler potential are reexamined, which arises in various approaches to supersymmetry breaking.When no-scale boundary conditions are given at the Grand Unified scale and universal gaugino masses are postulated, a bino mass is quite degenerate with right-handed slepton masses and the requirement that the lightest superparticle (LSP) be neutral supplemented with slepton searches at LEP200 severely constrains allowed mass regions of superparticles. The situation drastically changes if one moderately relaxes the assumption of the universal gaugino masses. After reviewing some interesting scenarios where non-universal gaugino masses arise, we show that the non-universality diminishes the otherwise severe constraint on the superparticle masses, and leads a variety of superparticle mass spectra: in particular the LSP can be a wino-like neutralino, a higgsino-like neutralino, or even a sneutrino, and also left-handed sleptons can be lighter than right-handed ones.
In the frame of an effective MSSM model without gaugino-mass unification at a grand unification scale, we set a lower bound on the neutralino mass based on the new WMAP data on ΩCDM (R-parity conservation is assumed). Our lower bound, mχ > ∼ 6 GeV, leaves much room for relic neutralinos significantly lighter than those commonly considered (mχ > ∼ 50 GeV). We prove that these light neutralinos may produce measurable effects in WIMP direct detection experiments of low energy threshold and large exposure.
“…where m t is the top mass, mt is the stop mass scale, and A t is the mass scale included in the trilinear scalar term [26]. We represent the top-stop loop contribution explicitly because it is the largest contribution in the Yukawa one.…”
We consider, in the context of the minimal supersymmetric standard model, the case where the gravitino weighs 10 6 GeV or more, which is preferred by various cosmological difficulties associated with unstable gravitinos. Despite the large Higgs mixing parameter B together with the little hierarchy to other soft supersymmetry breaking masses, a light higgsino with an electroweak scale mass leads to successful electroweak symmetry breaking, at the price of fine-tuning the higgsino mixing µ parameter. Furthermore the light higgsinos produced at the decays of gravitinos can constitute the dark matter of the universe. The heavy squark mass spectrum of O(10 4 ) GeV can increase the Higgs boson mass to about 125 GeV or higher.
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