In the CHORUS experiment, a small loss of events is visible in the upstream part of the target stack (Fig. 12). Since the ratio of found to predicted vertices remains constant over the stack, we conclude that this inefficiency can be assigned to pattern recognition difficulties in the electronic detectors. In the present design, this capability has been dramatically improved and one expects that this effect will be much weaker.
The scan-back efficiency in the target stack remains constant over the depth of the stack traversed. The possibility of using thicker target stacks, thus adding more mass while keeping the amount of electronic detectors constant, will therefore be tried out in the test beam.