The electroweak fine-tuning measure ${\mathrm{\Delta }}_{\mathrm{EW}}$ allows for correlated supersymmetry (SUSY) soft terms as are expected in any ultraviolet complete theory. Requiring no less than 3% electroweak fine-tuning implies upper bounds of about 360 GeV on all Higgsinos, while top squarks are lighter than $\sim 3\mathrm{TeV}$ and gluinos are bounded by $\sim 6–9\mathrm{TeV}$. We examine the reach for SUSY of the planned high luminosity (HL: $3{\mathrm{ab}}^{-1}$ at 14 TeV) and the proposed high energy (HE: $15{\mathrm{ab}}^{-1}$ at 27 TeV) upgrades of the LHC via four LHC collider search channels relevant for natural SUSY: 1. gluino pair production followed by gluino decay to third generation (s)quarks, 2. top squark pair production followed by decay to third generation quarks and light Higgsinos, 3. neutral Higgsino pair production with QCD jet radiation (resulting in monojet events with soft dileptons), and 4. wino pair production followed by decay to light Higgsinos leading to same-sign diboson production. We confront our reach results with upper limits on superpartner masses in four natural SUSY models: natural gravity mediation via the 1. two- and 2. three-extra-parameter nonuniversal Higgs models, 3. natural minilandscape models with generalized mirage mediation and 4. natural anomaly mediation We find that while the HL-LHC can probe considerable portions of natural SUSY parameter space in all these models, the HE-LHC will decisively cover the entire natural SUSY parameter space with better than 3% fine-tuning.

• Received 21 August 2018

DOI:https://doi.org/10.1103/PhysRevD.98.075010

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Published by the American Physical Society