Particle identification with the opal jet chamber in the region of the relativistic rise

Abstract An important goal of the OPAL jet chamber is particle identification at high momenta by exploiting the relativistic rise of the energy loss. Extensive tests have been performed with the full scale prototype of the OPAL jet chamber to measure the energy loss in an argon-methane-isobutane mixture as function of momentum and particle species. The measurements were done under various operating conditions in order to optimise the operating point, to investigate sources of systematic errors, to monitor the stability of the energy loss measurement and to develop calibration procedures. The particle separation capability in the region of the relativistic rise has been studied at gas pressures of 3 and 4 bar. The adopted operating point represents a reasonable compromise between the requirements for particle identification and tracking accuracy.