Abstract
Anomaly-mediated supersymmetry breaking (AMSB) models seem to have become increasingly implausible due to 1. difficulty in generating a Higgs mass m(h)~125 GeV, 2. typically unnatural superparticle spectra characterized by a large superpotential mu term and 3. the possibility of a wino-like lightest SUSY particle (LSP) as dark matter now seems to be excluded. In the present paper we propose some minor modifications to the paradigm model which solve these three issues. Instead of adding a universal bulk scalar mass to avoid tachyonic sleptons, we add distinct Higgs and matter scalar soft masses which then allow for light higgsinos. To gain accord with the measured Higgs mass, we also include a bulk trilinear soft term. The ensuing natural generalized AMSB (nAMSB) model then has a set of light higgsinos with mass nearby the weak scale m(W,Z,h)~100 GeV as required by naturalness while the winos populate the several hundred GeV range and gluinos and squarks occupy the multi-TeV range. For LHC searches, the wino pair production followed by decay to same-sign diboson signature channel offers excellent prospects for discovery at high luminosity LHC along with higgsino pair production leading to soft dileptons plus jet(s)+MET. A linear e^+e^- collider operating above higgsino pair production threshold should be able to distinguish the AMSB gaugino spectra from unified or mirage unified scenarios. Dark matter is expected to occur as a higgsino-like WIMP plus axion admixture.
Highlights
The discovery of D-branes in superstring models in the 1990s [1] ushered in new avenues for particle physics model building
We have proposed a new anomaly-mediation paradigm model which evades the problems of 1) too low a value of mh, 2) unnaturalness, and 3) winolike lightest SUSY particle (LSP) which may be excluded by a lack of indirect WIMP detection (IDD) of dark matter
Our new model, dubbed natural anomaly-mediated SUSY breaking or nAMSB, merely incorporates the inclusion of nonuniversal bulk scalar masses and a bulk trilinear term A0. The former allows for small μ as required by naturalness and leads instead to a Higgsino-like weakly interacting massive particles (WIMPs) as LSP
Summary
The discovery of D-branes in superstring models in the 1990s [1] ushered in new avenues for particle physics model building. In the mAMSB model, the trilinear soft terms given by Eq (3) are generally not large enough to lift the predicted value of mh into the 125 GeV range unless sparticle masses are very heavy—in the vicinity of tens of TeV [15,16,17]. Ðm2Q3 þ m2U3 þ A2t Þ ln ðΛ2=m2SUSY Þ with ft the top Yukawa coupling, Λ is as high as mGUT, and mSUSY ∼ 1 TeV This measure has been oversimplified by neglecting the m2Hu contribution to its own running so as not to allow for radiatively driven naturalness, where large high-scale soft terms are driven by radiative corrections to natural values at the weak scale [29,30].
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