Searches for supersymmetric higgsinos with the ATLAS detector

A search for supersymmetric partners of the Higgs and gauge bosons (charginos and neutralinos) is presented in this work, using the data from the ATLAS experiment collected at LHC. Considerations on the naturalness of the Higgs boson mass suggest that the two lightest neutralinos might be a mix of the partners of the Higgs boson and could have a similar mass. Using this scenario as a reference, two analyses are presented. One has a final state with pairs of electrons or muons with low transverse momentums coming from the decay of the two lightest neutralinos, high missing transverse momentum generated by neutralinos which are non detectable, and an energetic jet coming from QCD initial state radiation. The second one is characterised by a final state with disappearing tracks, and high missing transverse momentum. Results are shown for the analysis obtained with 36 fb$^{-1}$, and limits are set on the mass parameter of the higgsinos.