Development and test of a presampler for the H1 detector instrument with silicon detectors

Inactive material in front of a calorimeter leads to a worsening of the energy resolution and energy reconstruction. A silicon instrumented presampler provides the opportunity to correct for the energy loss of electrons in the inactive material and thus improve the energy reconstruction and resolution. The difference of the interaction probability of electrons and hadrons with the material in front of the presampler can be exploited for particle identification. Test measurements were performed with a silicon layer of a total area of 25 x 25 cm2 in front of the H1-Pb-LAr calorimeter at the CERN-SPS. A thin target of 1.5Xo (0.09λo) NaI was put in front of the silicon to mimic inactive material. The improvement of the energy resolution of the electromagnetic calorimeter with the silicon presampler was determined to be ∝ 10%√GeV for an electron energy of 10-50GeV. The difference in the particle multiplicity, for incident electrons and pions, hitting the silicon presampler had been used for electron-pion separation. At an electron efficiency of 90% and a particle energy of 30GeV the pion misidentification was measured to be 4.4%. The simulation of the interaction of pions with the NaI-target requires a good calculation of the very first inelastic pion-nucleus interaction. Satisfying agreement can be obtained by simulating the response of the silicon presampler with the Scaling-model implemented in the CALOR program. The CALOR program has been used to simulate the response of a silicon instrumented presampler in front of the backward calorimeter of the H1-detector to jets. At an electron efficiency of 90% (99%) the hadron misidentification has been determined to be 5.4% (12%). (orig.)