The use of a pair of time projection chambers as a wide-angle vertex detector for the OMEGA' spectrometer at CERN

A pair of time projection chambers has been tested in an 85GeV/c\u3c0 12 beam. The chambers were placed inside the magnetic field of the \u3a9\u2032 spectrometer at CERN. A description of the device and the associated electronics is given. Results obtained on track and vertex reconstruction accuracy are presented

The \u201cRoman pot\u201d spectrometer and the vertex detector of experiment UA4 at the CERN SPS collider

We describe the apparatus used in experiment UA4 to study proton-antiproton elastic and inelastic interactions at the CERN SPS Collider. Elastically scattered particles, travelling at very small angles, are observed by detectors placed inside movable sections (\u201cRoman pots\u201d) of the SPS vacuum chamber. The deflection in the field of the machine quadrupoles allow the measurement of the particle momentum. Inelastic interactions are observed by a left-right symmetric system of trigger counter hodoscopes and drift-chamber telescopes. The apparatus reconstructs the interaction vertex and measures the pseudorapidity \u3b7 of charged particles in the range 2.5 < \u2016\u3b7\u2016 < 5.6