Performance of the ATLAS global transverse-momentum triggers at $\sqrt{s}$ = 8 TeV

The global transverse momentum triggers of the ATLAS experiment at the CERN Large Hadron Collider are designed to select collision events with non-interacting particles passing through the detector and events with a large amount of outgoing momentum transverse to the beam axis. These triggers use sums over the full calorimeter, and therefore can be very sensitive to the average number of interactions per bunch crossing. This note describes the methodology and the performance of the transverse-momentum trigger algorithms that were deployed during the 2012 ATLAS data taking campaign at 8 TeV center-of-mass energy. Improvements over what was done in 2011 resulted in better efficiency in 2012 despite a doubling of the per bunch crossing luminosity.