Test beam studies of the GasPixel transition radiation detector prototype

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 View the MathML source11μm and a vector angular accuracy of about 10 mrad for a beam incident angle of 10°. For particle identification studies the detector was filled with a Xe/CO2 (70/30) mixture. A block of transition radiation radiator of 19 cm 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 5 GeV 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.