Performance and response of scintillating fiber modules to protons and pions

The HERMES experiment located at DESY measures scattering reactions of 27.5 GeV positrons or electrons impinging on a gaseous hydrogen target. The target will be surrounded by a recoil detector dedicated to measure recoiling nucleons. This detector will operate a scintillating fiber tracker to identify and track protons for momenta up to 1400 MeV/cc. Scintillating fibers are an ideal tool to combine energy and position measurements for charged particles in an intermediate momentum range. They offer a high granularity while keeping the mechanical construction and material density at a minimum. Modules build from Kuraray SCSF-78 fibers of 1 mm diameter were tested at a secondary beam of positive charge at various momenta from 300 to 900 MeV/cc. Their read-out was performed using customized VME modules with front-end boards based on GASSIPLEX chips. The energy response and particle identification properties of the modules were tested. The results obtained in this study meet the specified design criteria.