Offline software meeting minutes

[David Lawrence <davidl@jlab.org>]

Hi Offliners,

    The minutes from last Thursday's offline software meeting have been 
posted at:

http://www.jlab.org/Hall-D/software/wiki/index.php/July_3%2C_2008_Software

and are copied below.

Regards,
-David

=======================

Attendees: David L. (chair), Mac M., Mark I., Simon T., Sebastien P., 
Beni Z., Elliott W., Elke A., Jim S., Elton S., Eugene C., Alex S.

On the phone: Mihajlo K.

Sebastien gave a presentation on the current status of charged track 
reconstruction for CLAS12 in Hall-B. The CLAS12 detector consists of a 
central region with a solenoidal magnetic field and a forward region 
with a toroidal magnetic field. The tracking systems consists of silicon 
detectors in the barrel region and drift chambers in the forward region 
surrounding the torus magnet.

An overview of the basic track finding method was given which included 
rejection of uncorrelated noise.

The fitting procedure uses a Kalman filter method. The resolution of the 
left-right ambiguity is integrated into the fitter such that hits for 
which the L/R is clearly resolved, are used while hits without use the 
wire position with large errors. Subsequent passes can resolve more hits 
as the track is refined.

Misalignment studies have been done which demonstrate the effect a 
specific set of misalignments and translations of the detectors has on 
the reconstructed track resolution.

Sebastien noted that the result of the fit has a dependence on the 
starting parameters.

One of the issues CLAS12 has is the matching of tracks from the 2 
magnetic field regions. Matching efficiency was shown to be a somewhat 
strong function of the DC occupancy with 98% at zero percent occupancy 
and 82% at 7 percent occupancy.

Finally, tracking resolutions were shown for both the drift chambers 
alone and the drift chambers combined with the forward silicone tracker 
(FST). The FST provided very large improvements in the vertex resolution 
and significant improvements in the momentum and angular resolutions. 
The notable exception was the polar angle theta which showed only a 
modest improvement with the inclusion of the FST.

-- 

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  David Lawrence Ph.D.
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