I reconstructed tracks for R2 DC using the single superlayer tracking
program. The hits were selected from HBT and only those within +-5 degrees
from the midplane were accepted.
I analyzed run 3606. The main torus was set at half of the full field.
I assumed 500ps/ch in the raw TDC spectra. The gas was AR/CO2 90/10
mixture (by volume). Nearly 5000 sample tracks were used for both R2
axial and stereo superlayer (sector 4 only).
Here are some results that I found (for region 2 sector 4 only).
1. The absolute layer efficiency was 98.0+-0.5%.
2. The single layer resolution was 600 microns. This was obtained using
RAW drift times (fitted to straight tracks). NO corrections at all except
a constant offset was removed. Tracks are distributed mainly in the
forward and intermediate region of the sector.
3. The longest maximum drift time tmax at forward angle (wire #1-#16) is
750ns in the axial superlayer. It decreases at 110ns/Tesla as the B field
becomes smaller at large scattering angle. A liner dependence of the maximum
drift time on the strength of the B field roughly holds for 0.4T<B<0.9T.
4. The maximum drift time in the stereo superlayer is 100ns longer compared
to the nearby region in the axial layer.
5. A single distance-time correlation function x(t/tmax) gives good results
for both superlayers, or in another word, for different tmax's.
6. It seems that Garfield simulation can not reproduce the results in the
case the B field is non-zero for the gas mixture.