  The ATLAS Transition Radiation Tracker (TRT) is the outermost of the three
sub-systems of the ATLAS Inner Detector at the Large Hadron Collider at CERN.
In addition to its tracking capabilities, the TRT provides particle
identification (PID) ability through the detection of transition radiation
X-ray photons. The latter functionality provides substantial discriminating
power between electrons and hadrons in the momentum range from 1 to 200 GeV. In
addition, the measurement of an enhancement of signal time length, which is
related to high specific energy deposition (dE/dx), can be used to identify
highly ionizing particles, increasing the electron identification capabilities
at low momentum and improving the sensitivity of searches for new physics. This
talk presents the commissioning of TRT PID during early 2010 7 TeV data taking.
Performance in 2010 and 2011 demonstrating the TRT's ability to identify
electrons, complementary to calorimeter based identification methods, will also
be shown.
