The Mac Detector

Abstract The MAC detector at PEP recorded data for an integrated luminosity of 335 pb −1 between 1980 and 1986. The design of this low-cost MA gnetic C alorimeter was optimized for electron and muon identification, as well as for the measurement of hadronic energy flow. Muon identification is available over 96% of the solid angle, and MAC was the first detector to make large-scale use of gas-sampling calorimetry. Electromagnetic calorimetry in the central section employs alternating layers of lead and proportional wire chambers (PWCs), and hadron and the remaining electromagnetic calorimetry is accomplished with iron plate and PWC layers. A relatively small central drift chamber in an axial magnetic field provides pattern recognition and modest momentum determination. An outer blanket of drift tubes completes the muon identification system. During the latter two years of operation an innovative “soda straw” vertex chamber made more precise lifetime measurements possible. With an evolving trigger system and highly automated data acquisition system, this modest detector has exceeded most of its designers' expectations and has produced a gratifying spectrum of physics results.