The first combined cosmic run of TRT and SCT since SR1.
The entire SCT barrel and the following part of the TRT barrel was read out.
Alignment of the Barrel
Ran the L1 TRT barrel alignment using data from the entire M6 run.
Track requirements:
> 20 TRT hits
> 5 SCT hits
rejected tube hits
Total Events: 11,319
Tracks: 3,973
Aligned 5 DoF.(2 Translations, 3 Rotations)
Used internal alignments derived for SCT.
Saw convergence after a few iterations.
Overall resolution (entire barrel, no explicit endcap rejection) improved from 500 to 330 microns.
L2 Alignment was also run on the TRT Barrel in M6.
Convergence of the modules was much worse.
No increase in tracks and hits with iteration.
Most L2 alignments were larger than expected, 0(500 microns) from Survey.
In the end the decision was made to only put the L1 alignment constants in the database.
Before the SCT internal alignment, the TRT L1 alignment was run on three subsets of the M6 data
In M6 the barrel was aligned with 5 DoF and with 3 (dx, rotz, roty).
Same track selection as above.
We saw conversion of the alignment parameters as a function of iteration, and increase in the number of hits and tracks.
Overall resolution (entire barrel, no explicit endcap rejection) improved from 450 to 300 microns.
The results are given in the following:
Full report of barrel alignment in M6 given here.
Alignment of the Endcap A
In M6 ~1/3 of endcap A was readout.
The tracking in the endcaps from M6 was first seen to be very bad.
Pattern recognition was failing and track fits were horrible.
The search road in pattern rec was widened to O(mm) allowing for some track finding.
Ran the L1 alignment on the endcap, this was an alignment wrt SCT barrel.
There was no TRT Calibration for the endcaps at the time.
Tracks with TRT endcap hits were required to have > 20 TRT hits and > 5 SCT hits.
Ran the alignment with both 6 DoF and 4 DoF (3 translations + rotations around Z)
Results were consistent, but convergence was worse for 6 DoF, decided to put the results with 4 DoF in the DB.
The following are the constants that were derived, (see however endcap shift above)
The following plot shows the TRT residual before(red) and after(black) the L1 alignment.
Note: There is no TRT calibration used.
Full report of endcap alignment in M6 given here.