Simulating charge collection in silicon pixel detectors

A simulation of the charge collection mechanism in silicon pixel detectors has been performed. Effects due to diffusion, δ-rays production and magnetic field have been taken into account. The VLSI cells response has been modelled assuming Gaussian noise and Gaussian threshold variation centred on typical values. A 5 × 5, 100 μm pitch, square pixel array, with the central pixel (surrounded by its 8 first and 16 second neighbours) uniformly irradiated by MIPs with different incident angles, has been considered. Its geometry has been varied looking for cluster distribution and attainable spatial resolution for both digital and analogue read out. The simulations have been compared with the results obtained with digital and analogue hybrid silicon pixel detectors and show, in the limits of the Monte-Carlo uncertainties, a good agreement with experimental data.