Stau pairs from natural SUSY at high luminosity LHC

Natural supersymmetry (SUSY) with light higgsinos is perhaps the most plausible of all weak scale SUSY models while a variety of motivations point to (right) tau sleptons as the lightest of all the sleptons. We examine a SUSY model line with rather light right-staus embedded within natural SUSY. For light stau_1 of a few hundred GeV, then the decays stau_1 -> τ1,2^0 and ν_τ_1^- occur at comparable rates where the (higgsino-like) _1^± and _2^0 release only small visible energy: in this case, the expected τ^+τ^- + signature is diminished from usual expectations due to the presence of the nearly invisible decay mode _1 -> ν_τ_1^-. However, once m_1> ~m(bino), then decays to binos such as _1 -> τ_3^0 open up where _3^0 decays to higgsinos plus W^±, Z^0 and h at comparable rates. For these heavier staus, then stau pair production gives rise to diboson+ events which may contain 0, 1 or 2 additional hard τ leptons. From these considerations, we examine the potential for future discovery of tau-slepton pair production at high-luminosity LHC. While we do not find a 5σ HL-LHC discovery reach for 3000 fb⁻¹, we do find a 95% CL exclusion reach, ranging between m_1:100-450 GeV for m_1^0~ 100 GeV. This latter reach disappears for m_1^0>~ 200 GeV.