hi,
i went through quite a few events in nsed in an attempt to trace down
inefficiencies in the wire chamber reconstruction. the enclosed
histograms break down the misreconstructed events in one paddle
combination (0-14) (i also did 1-14, 1-13). the sample data set was
taken from runs 705-708 (first 25k events in each), and strict cuts were
placed on timing and coplanarity.
black: events w/o 3 segments; mostly no hits in entire chamber,
partially an issue of acceptance; found 1 tree event
blue: no fast fit track; mostly overloads (too many segment
combinations, fixable by loosening cut)
green: no newton fit track: mostly from 3-4 stub events, with ~8/18 hits
red: good events
conclusion: the inefficiencies are mostly due to wire chamber
efficiency and calibration, although some improvements are possible in
the sofware to salvage these events. the forward events are less
efficient because of missing hits, miss-calibrations between adjacent
cells (these stubs are almost never 3 hits in one cell), and a more
complicated acceptance region for curved tracks (as opposed to a true
inefficiency).
some things which should be improved in software: a) make more of an
effort to use real hits instead of fake stubs (no hit data). this is
important for the newton fitter. b) smarter (dynamic) cuts so i) that
we don't loose real stubs/segs/tracks, and ii) we don't get
bloated/overloaded with too many tracks. hopefully better calibrations
will abate this problem, anyways. in my limited viewing of the data, i
did not find any obvious bugs in the reconstruction software, and almost
of the missed events were due to the above explanations.
finally, if possible, i would like to take a short unpol H run at .5
sccm (~1/2 hr) sometime, to have some more recent data for WC
callibrations, and testing reconstruction efficiencies. since the runs
700-800, some of the missing cells have been restored. i would like to
see how this improves our current reconstruction.
--chris
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