Hadronic particle identification with silicon detectors by means of dE/dx sampling

In order to study Generalized Parton Distributions (GPD) at future fixed-target Deep Inelastic Scattering (DIS) experiments, a detector is needed to observe particles at angles larger than can be covered by the usual forward-angle spectrometer used in this type of experiments. This additional (recoil) detector will determine the exclusivity of the measurements, which cannot be guaranteed by the main spectrometer due to its insufficient energy resolution. Within the limited space available in the target area of such an experiment, the recoil detector must accomplish particle identification as a stand-alone detector, up to particle momenta of 1.3 GeV c−1. Using Monte Carlo simulations it has been investigated to what extend an energy loss measurement with a small barrel shaped detector consisting of a few layers of silicon sensors can be used to realize this goal. It turns out that a rough estimate of the momentum is necessary in this case, which can be obtained by measuring the curvature of the tracks in the strong magnetic field employed by the polarized targets used in this type of experiments. Because these studies rely heavily on calculated energy loss distributions as produced by the Monte Carlo code, a beam test with a mixed proton-pion beam has been carried out at CERN to verify the results of the simulation. The beam test results presented here confirm the predicted particle identification capabilities of a detector based on multiple sampling of ionization tracks in silicon up to 1.3 GeV c−1.