Upgrade of the first level muon trigger in the end-cap new small wheel region of the ATLAS detector

The luminosity levels foreseen at the LHC after the 2018 LHC upgrade will tighten the demands on the ATLAS first level muon trigger system. A finer muon selection will be required to cope with the increased background and to keep the trigger rate for 20GeV/c p_T muons as before. The introduction of new detectors in the small wheel region of the end-cap muon spectrometer will allow to refine the current trigger selection, allowing to increase the rejection power for tracks not coming from the interaction point, thus to find candidate muon tracks within 1 mrad angular resolution and within the 500 ns available latency. The on-detector trigger logic will require a coincidence of eight layers of small thin gap chambers detector pads to determine the trigger regions-of-interest. The charge information from the detector strips of the selected regions-of-interest will be sent to the off-detector trigger logic, which will calculate the strip centroids and extrapolate the muon tracks. The muon tracks information will be finally sent to the end-cap sector logic, which will combine the big wheel and the new small wheel trigger data, and provide the trigger muon candidates to the ATLAS central trigger.