Cosmic-Ray Tests Of The Zeus Barrel Calorimeter Modules

The ZEUS barrel calorimeter consists of 32 wedge-shaped modules constructed using alternate layers of depleted uranium and scintillator with one radiation length sampling. In this paper we summarize tests made on 22 of these modules by measuring their response to hardened cosmic rays. We describe the cosmic ray facility, the data taking, the track reconstruction, the data analysis, and the module testing. These tests include the uniformity, both tower-to-tower and module-to-module, in the response to minimum ionizing particles, the mapping of this response as a function of lateral position of the particles inside a given tower, and the measurement of the number of photoelectrons produced by a minimum ionizing particle. In addition, we present data on the stability of the current in the photomultiplier tube generated by the natural radioactivity of the uranium.