1. Stepan Stepanyan presented code schematics and some results
on progress achieved in track matching, particle identification,
and the building of the final event. The reconstruction code
is geared towards electron scattering experiments, and starts with
identification of electron candidates. Other charged particles
are identified by using momentum (from DC reconstruction) and
time-of-flight. Photon and neutrons are identified by their
differences in shower development in EC and their beta values.
The code works within the RECSIS framework. A schematics is
shown in the attached
postscript file .
Everyone should take a
look at this, as there is a good chance that this will be part
of the first implementation of an event reconstruction code
for CLAS.
Also see individual report below.
2. Kim Egiyan presented a first look at the time resolution of
single strips of EC. He demonstrated that the individual strips
have to be calibrated one by one (there are 1296 strips!) for
optimal resolution.
Also see individual report below.
3. Konstantin Mikhailov presented some events that appear to be coming from a source far upsteam of the targets. He looked at zero B-field runs ith and without targets. Possible candidate for such events is beam-gas interaction in the beam pipe or other beam - vacuum pipe events. The events have energies of up to hundreds of MeV to GeV, and look like electrons. Additional shielding around the beam pipe upstream of CLAS would probably be sufficient to get rid of them. The relative frequency of these events was not clear. It is possible that for running with very thin targets (gas, this foils) they may constitute a non-negligible background. Further analysis is warranted.
4. Bogdan Niczyporuk presented the implementation of the updated mini-torus coil geometry. Due to difficulties he had with the more complicated geometry in the upstream part of the coil,the present implementation may have to be further refined.
Stepan Stepanyan:
Code for track matching, particle identification and building a final event
was presented. Code is written on f77 and works in the RECSIS framework.
It uses the information posted by detector reconstruction codes after Pass 0
analyses. At the moment this information is taken directly from common
blocks due to the incompleteness of information in some of the
reconstruction BOS banks (SCRB, TRKL ...).
The proposal is to include the code in the CLAS tree for common use.
That can help other users to test different ideas for detector analyses,
trigger definitions, get time based tracking to move on, start to
think about final event format in mDST and so on.
Kim Egiyan:
First steps were presented on defining time constants for EC strips. The idea is to use the longest strip in one view to tag a relative time offsets in the other. The idea was tested using strip W35I as a trigger for U inner strips. For large energy deposition (electrons) in the strips the combined time resolution of two strips is about 0.6-0.8ns (for one strip this number will be smaller!). To complete this work precise determination of the effective path length (effective light speed in the strips) and conversion coefficients for the TDC's are needed. Also more statistics for strips at large scattering angles is required. The time walk for different strips was studded as well.