LHC luminosity and energy upgrades confront natural supersymmetry models

TL;DR

This paper assesses the potential of high luminosity and high energy upgrades of the LHC to detect natural supersymmetry models, focusing on specific search channels and confronting results with various SUSY frameworks.

Contribution

It provides a detailed analysis of the LHC upgrade reach for natural SUSY, incorporating electroweak fine-tuning constraints and multiple search channels across different SUSY models.

Findings

HL-LHC can probe significant parts of natural SUSY parameter space.

HE-LHC can fully cover natural SUSY models with less than 3% fine-tuning.

Certain superpartner masses are constrained by electroweak fine-tuning limits.

Abstract

The electroweak fine-tuning measure Delta(EW) allows for correlated SUSY soft terms as are expected in any ultra-violet 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 ~3 TeV and gluinos are bounded by ~ 6-9 TeV. We examine the reach for SUSY of the planned high luminosity (HL: 3 ab^{-1} at 14 TeV) and the proposed high energy (HE: 15 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 non-universal Higgs models, 3. natural mini-landscape 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.