Natural SUSY with a bino- or wino-like LSP
In natural SUSY models higgsinos are always light because μ^2 cannot be much larger than M_Z^2, while squarks and gluinos may be very heavy. Unless gluinos are discovered at LHC13, the commonly assumed unification of gaugino mass parameters will imply correspondingly heavy winos and binos, resulting in a higgsino-like LSP and small inter-higgsino mass splittings. The small visible energy release in higgsino decays makes their pair production difficult to detect at the LHC. Relaxing gaugino mass universality allows for relatively light winos and binos without violating LHC gluino mass bounds and without affecting naturalness. In the case where the bino mass M_1<~ μ, then one obtains a mixed bino-higgsino LSP with instead sizable w_1-z_1 and z_2-z_1 mass gaps. The thermal neutralino abundance can match the measured dark matter density in contrast to models with a higgsino-like LSP where WIMPs (weakly interacting massive particles) are underproduced by factors of 10-15. If instead M_2<~ μ, then one obtains a mixed wino-higgsino LSP with large z_2-z_1 but small w_1-z_1 mass gaps with still an under-abundance of thermally-produced WIMPs. Portions of the light wino parameter space may already be excluded by the IceCube upper bound on the spin-dependent neutralino-nucleon cross section. We discuss dark matter detection in other direct and indirect detection experiments and caution that the bounds from these must be interpreted with care. Finally, we show that LHC13 experiments should be able to probe these non-universal mass scenarios via a variety of channels including multi-lepton + etmiss events, WZ+etmiss events, Wh+etmiss events and W^\pm W^\pm +etmiss events from electroweak chargino and neutralino production.