Supersymmetry, naturalness and light higgsinos

Abstract

We compare and contrast three different sensitivity measures, ∆ −1 EW , ∆ −1 HS and ∆ −1 BG that have been used in discussions of fine-tuning. We argue that though not a fine-tuning measure, ∆ EW , which is essentially determined by the particle spectrum, is important because ∆ −1 EW quantifies the minimum fine-tuning present in any theory with a specified spectrum. We emphasize the critical role of incorporating correlations between various model parameters in discussions of fine-tuning. We provide toy examples to show that if we can find high scale theories with specific correlations amongst parameters, the value of the traditional fine-tuning measure ∆ −1 BG (which differs significantly from ∆ −1 HS only when these correlations are important) would be close to ∆ −1 EW . We then set up the radiatively driven natural SUSY framework that we advocate for phenomenological analyses of natural models of supersymmetry, and review the implications of naturalness for LHC and ILC searches for SUSY as well as for searches for SUSY dark matter.

Upper bounds on sparticle masses from naturalness or how to disprove weak scale supersymmetry

“…But does ∆ EW encapsulate all the fine-tuning, including high-scale effects, or is it just a lower bound on fine-tuning [38]?…”

Physics at a Higgsino factory

“…Such a discussion depends on the measure of supersymmetric naturalness which is adopted and how it is applied. Here, we will adopt the quantity ∆ EW [11][12][13][14][15][16][17] that leads to a model-independent bound on the magnitude of the superpotential parameter |µ| which is…”

Exploring charge and color breaking vacuum in non-holomorphic MSSM

“…In view of current experimental constraints, ElectroWeak Fine Tuning (EWFT) is a major concern in the phenomenological MSSM (pMSSM). In general, larger value of the bilinear Higgs mixing parameter of the superpotential (µ) significantly enhances the EWFT [32]. In the MSSM, even in scenarios that are devoid of any Higgsino like LSP, lower bound on |µ| is around 100 GeV via LEP limits on lighter chargino.…”

“…The NH higgsino mass parameter µ present in the NHSSM, contributes to the Higgsino content of the neutralinos, but does not have any signature on the tree level neutral scalar potential. The NHSSM can accommodate Higgsino DM even for very low value of µ resulting in the reduction of EWFT [32,[34][35][36]. The tri-linear NH parameters control the L-R mixing of corresponding squarks and sleptons.…”