Prospects for supersymmetry at high luminosity LHC

Abstract: Weak scale supersymmetry (SUSY) is highly motivated in that it provides a 't Hooft technically natural solution to the gauge hierarchy problem. However, recent strong limits from superparticle searches at LHC Run 2 may exacerbate a so-called Little Hierarchy problem (LHP) which is a matter of practical naturalness: why is m_{weak}<< m_{soft}? We review recent LHC and WIMP dark matter search bounds as well as their impact on a variety of proposed SUSY models: gravity-, gauge-, anomaly-, mirage- and gaugino-mediation along with some dark matter proposals such as well-tempered neutralinos. We address the naturalness question. We also address the emergence of the string landscape at the beginning of the 21st century and its impact on expectations for SUSY. Rather generally, the string landscape statistically prefers large soft SUSY breaking terms but subject to the anthropic requirement that the derived value of the weak scale for each pocket universe (PU) within the greater multiverse lies with the ABDS window of values. This {\it stringy natural} (SN) approach implies m_h~ 125 GeV more often than not with sparticles beyond or well-beyond present LHC search limits. We review detailed reach calculations of the high-lumi LHC (HL-LHC) for non-universal Higgs mass models which present perhaps the most plausible realization of SUSY from the string landscape. In contrast to conventional wisdom, from a stringy naturalness point of view, the search for SUSY at LHC has only just begun to explore the interesting regimes of parameter space. We comment on how non-universal Higgs models could be differentiated from other expressions of natural SUSY such as natural anomaly-mediation and natural mirage mediation at HL-LHC.