OPTIMIZATION OF CENTRAL PARTICLE TRACKING AT FUTURE HADRON COLLIDERS

Three detector media, gas, semiconductors and scintillating fibres, are compared in view of central tracking at future hadron colliders. As a result of this comparison, we opted for scintillating fibres and propose an optimized tracker arrangement: three cylindrical fibre shells, composed of two straight and two oblique layers each, will cover up to 1.75 rapidity. The individual polystyrene fibre diameters are 60 mum. The computed momentum resolution ranges from 0.3% to 10% for p(t) momenta between 10 GeV/c and 1 TeV/c. The vertex resolution along the collider axis amounts to 2.5 mm (for 4-degrees stereo angle). Unwanted contributions like gamma conversions (7%), secondary interactions (5%) and the number of curls per beam interaction are tolerable. Monte Carlo simulations show that occupancy is much less than 1% including curling and secondary tracks and that the fraction of ambiguous track combinations is small. Readout of track images will be performed via an electro-magnetically focused image intensifier with silicon pixels for random access readout. At comparatively slow drifts of the electronic images, it provides an image delay of about 1 mus and can therefore be gated by the first-level trigger of the detector. Consequently, it reduces the readout rate by about three orders of magnitude, thus eliminating most of the minimum bias background.