Stable massive particle in the ATLAS high-level muon trigger

Various models predict the existence of stable massive particles (SMPs) with a mass above the electroweak scale. Such particles are expected to be produced in the LHC collisions. Although events producing the SMPs are often accompanied with other activities like multijets, it is desired that the events can also be triggered by the presence of the SMPs themselves. The charged SMPs are minimum ionising and can be measured in muon detectors. The mass can be reconstructed from their time-of-flight (TOF). The ATLAS experiment has been developing trigger algorithms for SMPs in the high-level trigger (HLT), a software-based trigger system selecting events provided by the hardware-based level-1 trigger. The speed of SMPs is measured by their TOF obtained from track-by-track t0 of the ATLAS Monitored Drift Tubes (MDT) muon detector, and by the time measured by the RPC muon trigger detector. This contribution presents the trigger and computing performance of the algorithms using simulated events.