Simple model of calorimeter sampling response in a magnetic field

The fact that plastic scintillator ``brightens`` in the presence of a magnetic field has been known for some time. Recently, measurements have been extended to larger field strengths ( < 20 T ) and a saturation of the effect was observed for fields > 2.5 T. Thus the active element in a sampling calorimeter may be expected to have a signal increase of {approx} 6-8 % when immersed in fields of strength > 2.5 T. This brightening of the scintillator is independent of the orientation of the field. In addition to these effects, there has been reported an increase in the signal seen by sampling calorimeters due to incident electrons in the presence of a magnetic field. In contrast to the brightening effect, there does not appear to be saturation at the field strengths used (B < 2.5 T) and the magnitude of the effect appears to be somewhat larger than that expected from brightening alone, {approx}20% at 2.5 T. A comprehensive program has been mounted to study these problems in the context of CMS calorimetry and new results are expected momentarily. In particular, field strengths up to 3 T are employed, and field orientations parallel and perpendicular to the incident particle are to be explored