T0 Global and sector-by-sector
The postscript file for this page can be found here.
The plots drawn on this page are the following.
This plot shows the value of the 12 sector-by-sector rolling calibrations
(blue dots) and of the T0 global rolling calibration (red dashed line). The
y-scale is in ns.
This plot shows the final correction (in ns) applied to each of the 12 DIRC
sectors. The full T0 correction is the sum of the global calibration and of
the sector calibration.
During the PC passes, 13 DIRC timing corrections are computed: they are then
used during the ER passes to reconstruct physics data. These quantities are
called 'rolling calibrations' as they are updated from run to run: values
computed in the previous run are used as inputs on the procedure which
computes the new values.
There are one T0 global and 12 sector-by-sector T0 corrections. Before Run 5a
and the 18 series, only the global T0 correction was a rolling calibration. The
other 12 parameters were hardcoded in the reconstruction code.
These T0 calibrations are usually very stable: the global one can fluctuate at
the ns level but the sector-by-sector calibrations are pretty constant over
large sets of consecutive runs.
A bad sector-by-sector correction would hamper the reconstruction for tracks
crossing this sector (and the neighboor ones!). A bad global T0 correction
would screw up the whole DIRC reconstruction.
Back to the DIRC QA plots page