An improved Shashlyk calorimeter

Shashlyk electromagnetic calorimeter modules with an energy resolution of about 3%/root E(GeV) for 50-1000 MeV photons have been developed, and a prototype tested. Details of these improved modules, including mechanical construction, selection of wave shifting fibers and photo-detectors, and development of a new scintillator with improved optical and mechanical properties are described. How the modules will perform in a large calorimeter was determined from prototype measurements. The experimentally determined characteristics of the calorimeter prototype show energy resolution of sigma(E)/E = (1.96 +/- 0.1)% circle plus (2.74 +/- 0.05)%/root E, time resolution of sigma(T) = (72 +/- 4)root E circle plus (14 +/- 2)/E (ps), where photon energy E is given in GeV units and circle plus means a quadratic summation. A punch-through inefficiency of photon detection was measured to be epsilon approximate to 5 x 10(-5) (Theta(beam) > 5 mrad). (C) 2007 Elsevier B.V. All rights reserved.