Implementation of H → ττ End-of-Fill triggers in data taking for the ATLAS experiment at the Large Hadron Collider.

During proton-proton collision runs at the Large Hadron Collider (LHC), the delivered instantaneous luminosity to ATLAS decreases as the number of protons per bunch in the beam declines. Luminosity leveling helps maintain a constant instantaneous luminosity at the ATLAS detector, but the instantaneous luminosity drops toward the End-of-Fill (EOF) at the later stages of each run. Without adjustments, the trigger rate would reduce by several kHz, freeing up more bandwidth for the implementation of EOF triggers with loosened selection requirements. By loosening the requirements of a typical di-tau trigger designed for H → ττ events (where both τ leptons decay hadronically) during the leveling period, we showed an increase of over 35% in signal statistics which pass baseline analysis-level requirements while staying within acceptable firing rates. These EOF triggers enable broader physics reach within allowable bandwidth requirements. In particular, EOF triggers can bolster statistically limited analyses, such as measurements on the Charge-Parity property of the Higgs coupling to tau leptons, and enable measurements previously obstructed by trigger constraints.