Straw tube tracking detector (STT) for ZEUS

The luminosity upgrade of the HERA accelerator and the installation of the microvertex detector in ZEUS impose additional requirements on the pattern recognition and track reconstruction capabilities of the existing tracking detectors, particularly in the forward direction. The Straw Tube Tracker (STT) is designed to meet this need by improving the tracking efficiency and reliability of the ZEUS experiment in the forward direction. The STT was installed in 2001 and several improvements were made in the recent HERA shutdown. This paper describes the design and construction of the STT, test-beam performance.