Abstract
The requirement of electroweak naturalness in simple supersymmetric models implies the existence of a cluster of four light higgsinos with mass $\sim 100-300$\,GeV, the lighter the better. While such light compressed spectra may be challenging to observe at LHC, the International Linear $e^+e^-$ Collider (ILC) with $\sqrt{s}>2m_{\rm higgsino}$ would serve as both a SUSY discovery machine and a precision microscope. We study higgsino pair production signatures at the ILC based on full, \texttt{Geant4-}based simulation of the ILD detector concept. We examine several benchmark scenarios that may be challenging for discovery at HL-LHC due to mass differences between the higgsino states between $20$ and $4$\,GeV. Assuming $\sqrt{s}= 500$\,GeV and 1000\,fb$^{-1}$ of integrated luminosity, the individual higgsino masses can be measured to $1-2\%$ precision in case of the larger mass differences, and at the level of $5\%$ for the smallest mass difference case. The higgsino mass splittings are sensitive to the electroweak gaugino masses and allow extraction of gaugino masses to $\sim 3-20\%$ (depending on the model). Extrapolation of gaugino masses via renormalization group running can test the hypothesis of gaugino mass unification. We also examine a case with natural generalized mirage mediation where the unification of gaugino masses at an intermediate scale apparently gives rise to a natural SUSY spectrum somewhat beyond the reach of HL-LHC.
Highlights
The Standard Model (SM) of particle physics has been spectacularly confirmed across a broad array of measurements and often to a very high precision at the LHC
Before turning to the weak-scale fits, we investigate whether the three benchmarks could be described by other widely used constrained models, in particular
The results of various weak scale fits to the ILC1, ILC2, and nGMM1 observables are discussed
Summary
The Standard Model (SM) of particle physics has been spectacularly confirmed across a broad array of measurements and often to a very high precision at the LHC. Mass, which is just right to produce a radiative breakdown of electroweak gauge symmetry, and (3) the measured value of mh ≃ 125 GeV, which lies squarely within the prediction of mh ≲ 135 GeV required by the MSSM.1 In spite of these theoretical successes, many physicists have developed a large degree of skepticism regarding the eventual emergence of SUSY at experimental facilities. We propose a natural generalized mirage mediation (nGMM) benchmark model, which instead has gaugino mass unification at the mirage scale μmir 1⁄4 mGUTe−8π2=α ∼ 5 × 107 GeV, where α 1⁄4 4 parametrizes the relative amounts of modulus mediation versus anomaly mediation in SUSY breaking In this case, by determining the mirage unification scale μmir, ILC can measure the strength α of moduli vs anomaly mediation.
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