An Improved Shashlyk Calorimeter

Abstract Shashlyk electromagnetic calorimeter modules with an energy resolution of about 3 % / 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 σ E / E = ( 1.96 ± 0.1 ) % ⊕ ( 2.74 ± 0.05 ) % / E , time resolution of σ T = ( 72 ± 4 ) / E ⊕ ( 14 ± 2 ) / E ( ps ) , where photon energy E is given in GeV units and ⊕ means a quadratic summation. A punch-through inefficiency of photon detection was measured to be e ≈ 5 × 10 - 5 ( Θ beam > 5 mrad ) .