Speaker
Jochen Markert
(Goethe Universitaet Frankfurt)
Description
The HADES tracking system consists of 24 trapezoidal, planar 6-layered
lowmass multi-wire drift chambers (MDC) symmetrically arranged in six
sectors, forming four tracking planes (I-IV) of increasing size. The analog
part of the readout of the drift cell signals is done via ASD8-B (Analog
Shaper Discriminator ) chips for differential amplification, shaping and
discrimination. The chips deliver logical signals with variable width,
equivalent to the time the shaped signal exceeds a given threshold. The
logical signals are fed to TDC chips allowing to measure the Time-over-
Threshold (ToT) of the signal. A method has been developed to derive the
energy loss deposited in the drift cell from the drift signals ToT. Special
attention has to be paid to the unfolding of the dependencies of the ToT
from the track topology, the electric field and the different cell geometry
thus allowing to average over all drift cells taking part in a reconstructed
trajectory. An energy loss resolution of about 10% is achieved for minimum
ionizing particles and 7−8% for strong ionizing particles. The results are
comparable to standard energy loss measurements via the integrated
deposited charge.
Author
Jochen Markert
(Goethe Universitaet Frankfurt)
