Search

The European Physical Society - High Energy Physics Conference 2019, EPS-HEP 2019, Ghent, Belgium, Belgium, 10 Jul 2019 - 17 Jul 2019; Proceedings of Science / International School for Advanced Studies (EPS-HEP2019), 596 (2020). doi:10.22323/1.364.0596, The requirement of electroweak naturalness in simple supersymmetric models motivates the existence of a cluster of four light higgsinos with mass $100 - 300$ GeV, the lighter the better. While such light compressed spectra may be challenging to observe at the LHC, future $e^+e^-$ colliders with $\sqrt{s} > 2$m(higgsino) would serve as both a SUSY discovery machine and a precision microscope. We study signatures of higgsino pair production at the ILC based on full, Geant4-based simulation of the ILD detector concept. We examine several benchmark scenarios that may or may not be accessible to HL-LHC searches, with mass differences between the higgsino states between 4 and 20 GeV. Assuming $\sqrt{s}\geq$ 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 can allow extraction of gaugino masses to $3 - 20\%$ (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 the HL-LHC., Published by SISSA, Trieste

Physical review / D D 101(9), 095026 (2020). doi:10.1103/PhysRevD.101.095026, The requirement of electroweak naturalness in simple supersymmetric models implies the existence of a cluster of four light Higgsinos with a mass ∼100–300 GeV, the lighter the better. While such light compressed spectra may be challenging to observe at the LHC, the International Linear e+e- Collider (ILC) with s>2mHiggsino would serve as both a SUSY discovery machine and a precision microscope. We study Higgsino pair production signatures at the ILC based on a full, geant4-based simulation of the ILD detector concept. We examine several benchmark scenarios that may be challenging for discovery at the HL-LHC due to mass differences between the Higgsino states between 20 and 4 GeV. Assuming s=500 GeV and 1000 fb-1 of integrated luminosity, the individual Higgsino masses can be measured to 1%–2% precision in the 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 ∼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., Published by Inst.302363, Melville, NY

Proceedings of The 39th International Conference on High Energy Physics — PoS(ICHEP2018) - Sissa Medialab Trieste, Italy, 2019. - ISBN - doi:10.22323/1.340.0631 The 39th International Conference on High Energy Physics, ICHEP2018, Seoul, Korea, 4 Jul 2018 - 11 Jul 2018; Sissa Medialab Trieste, Italy 631 pp. (2019). doi:10.22323/1.340.0631, Data from the LHC at 7, 8, and 13 TeV, have, so far, yielded no evidence for new particles beyondthe Standard Model Higgs boson. However, the complementary nature of physics with e+e−collisions still offers many interesting scenarios in which new particles can be discovered at theILC. These scenarios take advantage of the capability of experiments at e+e−colliders to observeparticles yielding final states with missing energy and small mass differences, to observe mono-photon events with precisely controlled backgrounds, and to observe the full range of exotic decaymodes of the Higgs boson. The searches that an e+e−collider makes possible are particularlyimportant for models of dark matter involving a dark sector with particles of 10–100 GeV mass.In this talk, we will review the opportunities that the ILC offers for new particle discovery., Published by Sissa Medialab Trieste, Italy

EPS-HEP2017, Venice, Italy, 5 Jul 2017 - 12 Jul 2017; Proceedings of Science (EPS-HEP2017), 306 (2017)., Radiatively-driven natural supersymmetry, a theoretically and experimentally well-motivated framework, centers around the predicted existence of four light, nearly mass-degenerate Higgsinos with mass $\sim 100-200$ GeV (not too far above $m_Z$). The small mass splittings amongst the higgsinos, typically 4-20 GeV, results in very little visible energy arising from decays of the heavier higgsinos. Given that other SUSY particles are considerably heavy, this makes detection challenging at hadron colliders. On the other hand, the clean environment of an electron-positron collider with $\sqrt{s}>2m_{higgsino}$ would enable a decisive search of these required higgsinos, and thus either the discovery or exclusion of natural SUSY. We present a detailed simulation study of precision measurements of higgsino masses and production cross sections at $\sqrt{s}$ = 500 GeV of the proposed International Linear Collider currently under consideration for construction in Japan. The study is based on a Geant4 simulation of the International Large Detector concept. We examine several benchmark points just beyond the HL-LHC reach, with four light higgsinos directly accessible by the ILC, and the mass differences between the lightest SUSY particle and the heavier states ranging from about 4 to 20 GeV. It can be shown that their masses and production cross sections can be precisely measured to approximately 1\% precision or better. These precise measurements allow for extracting the underlying weak scale SUSY parameters, giving predictions for the masses of heavier SUSY states. These provide motivation for future high-energy colliders. Additionally, dark matter properties may be derived. Evolution of the measured gaugino masses to high energies should allow testing the hypothesis of gaugino mass unification., Published by SISSA, Trieste

A core prediction of natural Supersymmetry is the existence of four light higgsinos not too far above the mass of the $Z$ boson. The small mass splittings amongst the higgsinos -- typically 5-20\,GeV -- imply very little visible energy release from decays of heavier higgsinos. In particular, if other SUSY particles are quite heavy, as can be the case in SUSY with radiatively-driven naturalness, the higgsinos are extremely hard to detect at hadron colliders. The clean environment of electron-positron colliders with $\sqrt{s} > 2m_{\mathrm{higgsino}}$, however, would allow for a decisive search for the required light higgsinos. Thus, $e^+e^-$ colliders should either discover or exclude natural SUSY. We present a detailed study of higgsino pair production at the proposed International Linear $e^+e^-$ Collider which is under consideration for construction in Japan. A variety of precision measurements should allow for extraction of underlying parameters and provide a window onto physics at the grand unified scale.