Design of a silicon-tungsten calorimeter for the forward direction in the PHENIX experiment at RHIC

The PHENIX detector at RHIC has been designed to study hadronic and leptonic signatures of the new states of matter in heavy ion collisions and polarized proton collisions. The baseline detector measures muons in two muon spectrometers located forward and backward of mid-rapidity, and measures hadrons, electrons, and photons in two central spectrometer arms each of which covers 90 degrees in azimuth and 0.35 unit of rapidity where the existing electromagnetic calorimeters are installed. Further progress requires extending rapidity coverage for hadronic and electromagnetic signatures beyond the limits set by already built central spectrometer, in particular upgrading the functionality of the PHENIX muon spectrometers to include photon and jet measurement capabilities. Tungsten calorimeters with silicon pixel readout and fine transverse and longitudinal segmentation are proposed to attain this goal. The use of such a design provides the highest density and finest granularity possible in a calorimeter.