(Cremaldi, Reidy, student, 1/3 postdoc)

(a) Simulations--Mississippi has initiated a series of light collection studies for the Babar crystals using two ray tracing program, LTRANS and a more compact and flexible routine RayTrace, written by Lucien Cremaldi. We have investigated and reported on light collection in rectangularly, pyramidally, and hexagonally shaped CsI crystals. We have also considered the consequence of splitting the crystal near shower maximum with a front and back readout. We are investigating the direct coupling versus waveshifter option for photodiode placement. Studies have indicated significant differences in light collection due to crystal shape and photodiode placement. These results are presently being compared with real data on light yields. Ultimately the ray trace programs will be coupled to GEANT shower developement to optimize calorimeter performance.

(b) Experimental -- We are investigating the light output distribution from 25cm long trapezoidal crystals by mapping the light intensity at the rear face of the crystal with various source positions and using PMTs and PDs. Comparisons are being made with the simulation studies. We propose to do these same measurements using hexagonal crystals. In addition, studies of the WLS/PD and direct coupled PD configurations are underway.