A Study of coherent noise in binary Read-Out Systems and its applications to the ATLAS SemiConductor Tracker end-Cap

The ATLAS detector will surround one of the four interaction points of the Large Hadron Collider at CERN. ATLAS is a multi-purpose detector and is designed to discover and investigate a wide range of possible new physics. The ATLAS Semi-Conductor Tracker (SCT) is positioned in between the other two tracking detectors (PIXEL and TRT). The SCT will provide precision tracking for charged particles using silicon micro-strip detectors. The perfomance of the SCT system mainly depends on two parameters, which are noise occupancy and detection efficiency. Both of these parameters deteriorate with increasing noise in the system. It is therefore important to understand the effects of noise and to develop efficient methods to minimize it. Silicon detectors contribute to total noise mainly via their capacitance. Capacitance measurements on silicon micro-strip detectors are described. A detailed description of the effects of noise on the SCT modules with binary readout is given. Methods to measure common mode noise in binary readout systems are presented and have been successfully applied to ATLAS SCT end-cap modules. A GEANT4 based simulation for the SCT is performed under the Athena framework. The effects of increased SCT noise and inefficiency on the single track reconstruction efficiency have been studied. The single track reconstruction efficiency decreases to the specification value of 95% for SCT inefficiency of around 11% in the range |eta|< 1.5. The increased SCT noise does not have a significant effect on the single track reconstruction efficiency up to a maximum of 0.5% noisy channels.