Hi,
Just to let you know the current status in case any questions arise
about what we are doing regards to the WC resolution.
The attached figure shows the difference between reconstructed and
calculated momentum for ep elastic scattering. The calculated momentum
uses the reconstructed polar angle so there is a contribution from the
angular resolution as well but is probably small. The resolution is
around 44 MeV or 5.5% which is probably still only comparable to the
current resolution. There are still a few things that I would like to
try to improve this but at least the technique is working.
The difference with what is presented here is that this is based
purely on WC raw data. There are cuts on TOF data, trigger type or
anything else. I just require a negatively charged particle coming
from the target (40 cm H2 data was used, runs 6442-6457). Note I am
using the proper track angle in the time to position algorithm not
setting the angle to zero and apparently have no problems. When I look
at the distribution of hits it is fairly uniform across the cell with a
slight gap at the wire but nothing noticeable at the cell boundaries.
A benefit of this approach is that it is fast. It reconstructs tracks
from raw data at around 2,500 events per second on one of the bud's
which is about 20 times faster than we collect data and about 300 times
faster than we currently reconstruct. This means that one spud or bud
could keep up with the data acquisition easily and that changes or
calibration studies can be performed quickly on large data sets. So
maybe we didn't need to buy the bud's .... oh well :-)
If anything isn't clear send me an E-mail or phone 905-737-5269.
Cheers,
Douglas
26-415 M.I.T.
Tel: +1 (617) 258-7199
77 Massachusetts Avenue Fax: +1 (617)
258-5440
Cambridge, MA 02139, USA E-mail:
hasell@mit.edu
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