Search for electroweak production of supersymmetric states in compressed mass spectra in Run 2 with the ATLAS detector

Supersymmetry (SUSY) is one of the best studied extensions of the Standard Model. Although there is no sign of physics beyond the Standard Model yet, SUSY could still be hiding in more challenging signatures, like compressed mass spectra. These scenarios involve small mass differences between heavier SUSY particles and the lightest supersymmetric particle leading to the appearance of soft objects in the decay chain. A search is presented in which the lightest electroweakino states are nearly mass degenerate, leading to final states with two soft leptons, that have transverse momentum typically in the range from 3 to 20 GeV. These events are selected using triggers on missing transverse momentum (E${}_T$${}^{miss}$) that originates from the SUSY system recoiling against a jet from initial state radiation. To avoid any bias due to mismodeling in simulation, the usage of these triggers usually requires a hard cut on E${}_T$${}^{miss}$ at analysis level, which causes a significant loss in signal acceptance. Measuring the trigger efficiencies in data and simulation allows for an analysis selection with less tight requirements on E${}_T$${}^{miss}$ and thus to recover a considerable fraction of the signal events. This talk comprises studies about the measurement of the trigger efficiencies and how the inclusion of the low E${}_T$${}^{miss}$ phase space enhances the sensitivity of the search in a statistical combination.