Abstract
Testing the idea of naturalness is and will continue to be one of the most important goals of high energy physics experiments. It will play a central role in the physics program of future colliders. In this paper, we present projections of the reach of natural SUSY at future lepton colliders: CEPC, FCC-ee and ILC. We focus on the observables which give the strongest reach, the electroweak precision observables (for left-handed stops), and Higgs to gluon and photon decay rates (for both left- and right-handed stops). There is a “blind spot” when the stop mixing parameter X t is approximately equal to the average stop mass. We argue that in natural scenarios, bounds on the heavy Higgs bosons from tree-level mixing effects that modify the $$ hb\overline{b} $$ coupling together with bounds from b → sγ play a complementary role in probing the blind spot region. For specific natural SUSY scenarios such as folded SUSY in which the top partners do not carry Standard Model color charges, electroweak precision observables could be the most sensitive probe. In all the scenarios discussed in this paper, the combined set of precision measurements will probe down to a few percent in fine-tuning.
Highlights
Give up even if HL-LHC turns up empty
We present projections of the reach of natural SUSY at future lepton colliders: CEPC, FCC-ee and ILC
We focus on the observables which give the strongest reach, the electroweak precision observables, and Higgs to gluon and photon decay rates
Summary
We would like to understand how e+e− colliders can constrain natural supersymmetric scenarios. The largest contributions are generally those where the coupling appearing in the loop diagrams is the top Yukawa coupling yt ≈ 1 These include the F -term potential terms ytHu · Q3 2 + |ytHuuc3|2. We will discuss the parametric size of the leading loop effects and demonstrate how they arise as effective operators when stops and higgsinos are integrated out. The mass of the left-handed sbottom m2b1 could be written in terms of the stop physical masses and mixing angle as m2b1 = cos θtm2t1 + sin θtm2t2 − m2t − m2W cos(2β). The splittings originate from dimension five operators when the bino and wino are integrated out, and are of order m2Z/M1,2 We will ignore these splittings and treat all higgsino masses as equal to μ for the purpose of calculating loop effects
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