The forward muon detector (MUF) consists of two detection planes in each of the two end-caps of DELPHI. Each plane is made of 4 modules called quadrants, with dimensions 450 cm x 450 cm x 8 cm. Each quadrant contains two layers of 22 drift chambers crossed at 90 degrees. The basic detector cell is a 20 cm wide drift chamber equipped with a single anode wire and a delay line facing it. Each drift chamber provides 3 measurements : - Ta = the drift time - T1 and T2 = the propagation times of the induced anode pulse to both ends of the delay line. Because of the small number of charged particles crossing our detector, it is impossible to monitor the behaviour of each chamber individually. The monitoring is thus done at the layer level and our detector counts a total of 32 layers.
For each hit in a drift chamber, the measured times Ta, T1 and/or T2 are used to derive the coordinates X and Y of the charged particle impact point inside the chamber. These coordinates are only reconstructed if an association between the drift time Ta and the delay line times T1 and T2 can be achieved, what we call a triplet. This association is done on the basis of the quantity Tsum, defined as : Tsum = (T1 + T2 - 2.Ta) - L/Vdl where L is the total length of the delay line and Vdl the delay line velocity. This quantity must be between -50 ns and +50 ns for a triplet to be formed.
The accuracy on the X and Y coordinates is of the order of 5 mm, whether these coordinates are reconstructed in the drift direction or along the delay lines.