The ring shaped plastic scintillator detector STAR for forward angle reconstruction

The STAR-detector was built as one component of a 4π-detector setup for the test of the Gerasimov-Drell-Hearn sum rule. The STAR-detector will be employed to determine charged hadronic particle rates at small forward angles 1.7° ≤ ϑ ≤ 16.5° and to suppress atomic events. It consists of a scintillator plate and nine concentric scintillator rings with decreasing diameters. Each ring covers a polar angular range of Δϑ ≈ 1.85° and is realized by two half-rings with separate light readout. The optimized shape of the rings and the light guides was found through simulations with the Monte Carlo program SIMLIGHT.