New ATLAS Triggers Based on the Missing Et Significance

Missing transverse energy signatures are an important component of the ATLAS physics program. However, triggering on missing transverse energy in a high-luminosity hadron collider environment presents unique challenges, particularly due to the effects of pileup. ATLAS has therefore developed a set of triggers based on missing ET significance, a function of MET and scalar SumET which measures the amount of missing ET in standard deviations of the expected fake rate. We present the physical motivations, implementation from Level-1 upward, and expected performance of these new triggers.