Test beam studies of the GasPixel transition radiation detectorprototype

A combination of a pixel chip and a gas chamber opens new opportunities for particle detectors. These ''GasPix'' detectors have vector tracking features offering at the same time a L1 track trigger and a particle identification using transition radiation and dE/dX measurements. Test-beam and MC studies of tracking and particle identification properties have been performed with a GasPix prototype. The properties of the detector very much depend on the gas mixture. For one layer of the GasPix detector one can obtain a spatial accuracy down to 11@mm and a vector angular accuracy of about 10mrad for a beam incident angle of 10^o. For particle identification studies the detector was filled with a Xe/CO_2 (70/30) mixture. A block of transition radiation radiator of 19cm was installed in front of the detector. The pion rejection power using both cluster counting and full dE/dX methods was studied. It was shown that for 5GeV particles a single layer of the detector gives a pion suppression by about a factor of 7at an electron efficiency of 90%. Two layers of this detector provide a pion rejection factor of 50 at 90% electron efficiency. A comparison of the data and MC results is presented.