Minding the gap: testing natural anomaly-mediated SUSY breaking at high luminosity LHC

While the minimal anomaly-mediated SUSY breaking model (mAMSB) seems ruled out by constraints on Higgs mass, naturalness and wino dark matter, a slightly generalized version dubbed natural AMSB (nAMSB) remains both viable and compelling. Like mAMSB, nAMSB features winos as the lightest gauginos, but unlike mAMSB, nAMSB allows a small mu parameter so that higgsinos are the lightest of electroweakinos (EWinos). nAMSB spectra depend on the input value of gravitino mass m_{3/2}, where the lower range of m_{3/2} is excluded by LHC gluino pair searches while a higher m_{3/2} band is excluded by LHC limits on wino pair production followed by boosted hadronic wino decays. A remaining intermediate gap in m_{3/2} values remains allowed by present LHC searches, but appears to be completely explorable by high luminosity ugrades of LHC (HL-LHC). We explore a variety of compelling discovery channels that may allow one to close the intermediate gap in m_{3/2} values: 1. same-sign diboson +MET (SSdB) production arising from wino pair production, leading to same-sign dileptons plus MET, 2. trilepton production arising from wino pair production and 3. soft dilepton plus jet events from higgsino pair production, 4. top-squark pair production. From our signal-to-background analysis along a nAMSB model line, we expect HL-LHC to either discover or rule out the nAMSB model with 3000 fb^{-1} of integrated luminosity.