  ZE3RA is the software package responsible for processing the raw data from
the ZEPLIN-III dark matter experiment and its reduction into a set of
parameters used in all subsequent analyses. The detector is a liquid xenon time
projection chamber with scintillation and electroluminescence signals read out
by an array of 31 photomultipliers. The dual range 62-channel data stream is
optimised for the detection of scintillation pulses down to a single
photoelectron and of ionisation signals as small as those produced by single
electrons. We discuss in particular several strategies related to data
filtering, pulse finding and pulse clustering which are tuned to recover the
best electron/nuclear recoil discrimination near the detection threshold, where
most dark matter elastic scattering signatures are expected. The software was
designed assuming only minimal knowledge of the physics underlying the
detection principle, allowing an unbiased analysis of the experimental results
and easy extension to other detectors with similar requirements.
