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 at the 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 and could have a similar mass. Using this scenario as reference, the analysis searches for final states with pairs of electrons and muons with low transverse momentums coming from the decay of the second lightest neutralino into the lightest neutralino, high missing transvers momentum generated by neutrinos which are non detectable, and an energetic jet coming from QCD initial state radiation. Results are shown for the analysis obtained with 36 fb$^{-1}$, and limits are set on the mass parameter of the higgsinos.