Ssd Progress since the last meeting

Hey everybody,
here some parts of the progress we made in the last weeks.

Part of Jerome Baudot:

Jerome is working on the calibration.
Usually we should measure for the p- and n-side of a wafer the same amount of lost charge for a crossing particle.
Since the wafers (the ADC-chip) are not yet calibrated, we do not have a 100% matching of the charges.
These matching is needed for the clusterfinding algorithm.
85% of hits are of type (so called) 1-1 or 1-2, which means that the clusters on both sides of the wafer can exactly be matched to one hit.
15% of the hits are ambiguous, e.g. two particles close together, which produce 2 cluster on both sides, which produce 4 crossing points and therefore 2 hit solutions. See picture 0.

In the case of ambiguity a charge matching is used to find the correct hits, because it is expected, that the two matching clusters should carry the same amount of charge.

For the callibration the pulser runs a used, which pulse single strips with a certain ADC value. Picture 1 and 2 show the pulse values for the p- and n-side.
Picture 3 shows the ratio of the two pictures. For a perfect calibrated detector the picture should be completely green (=1). So it is visible, that some chips have to be calibrated. The white parts steem from chips, where the pulse system does not work.
(Click on the picture to enlarge. A new window will open.)


Picture 1: Mean response per chip. P-Side. Pulsing ladder 1 and 9 did not work.	Picture 2: Mean response per chip. N-Side. Pulsing ladder 1 and 9 did not work.	Picture 3: Ratio of p- to n-side. The wite parts come from a non working pulser for the chip. (The Chip works!!) The picture shows that most of the ratios are close to one. Only ladder 7 (which had a high voltage problem) and some chips must be calibrated.

Picture 3 shows, that some wafers need to be calibrated, to ensure a good cluster matching. Picture 4 shows the difference in the p/n-side ratio for two different runs. The difference is smaller than 5%.

Picture 4: The difference of two ratio pictures of two different runs. There values are distributed around zero (as expected), and show a difference smaller than 5% between two runs.

The calculated calibration values have to be filled into a database and be normalized (all chips should see the same pulse value). This will be done in the next weeks (after the upcoming conferences). After the calibration values are in the database and used by the cluster finding algorithm, the improvement of hit-finding (e.g. in the alignment) will be checked.
More information of Jeromes work can be found Here.

Joergs work: The alignment:
The alignment procedure is stopped in the moment,
because we realized, that we get different alignment parameters for different magnetic fields.
After playing with no field data and registering a strange behavior, I seperated the so far used data depending on the magnetic field.
Using the same global alignment parameters on these sets shows different behaviors for each of them. Since they should all look the same, it is clear, that we cannot do an alignment, which is correct for all data we use. So all our up to now alignment parameters (global and ladder alignment) are not usable.
(Click on the picture to enlarge. A new window will open.)


Picture 4: Residual in x agains phi for data with magnetic field.	Picture 5: Residual in x agains phi for data with reversed magnetic field.	Picture 6: Residual in x agains phi for data with no field data.

We discussed about the reason of this behavior and Lilian believes, that we are not using the right option parameters to get the data.
Therefore, Lilian asked for some processed data:

Here is the part of his email including the data:

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During one of the last S&C meeting you mentioned submitting a request. Here it comes :

20 kevents of CuCu200 (minbias) 6054020 for instance
100 kevents of CuCu200 (no field) 6065037 and 6065045 for instance
20 kevents of CuCu62 (minbias)

I know that people moved to 62 GeV data to solve SVT problems recently. The data must be with the TPC and if possible with the SVT. The tracking should be restricted to the TPC (unless people are confident in the tracks found by EST in the SVT) but the SVT and SSD hits should be written in StEvent. The option for the SSD are (ssddat and spt).
--------------------------------------------------------------------------------------------------------------

Since it does not make sense to process any of our own processed data, we stopped the alignment until we can use the data, mentioned above.
These data should not show any variation for different kind of fields.

Lilian and Jonathan:

Lilian is in the moment in his well-deserved holidays.
Before, he was working with Jonathan on the ITTF tracking, and he was trying to produce compress pedestal calibration files and debugging our codes. Jonathan has managed to run the ITTF tracking on simulated data.
Pictures 7, 8 and 9 show the improvement of the z, x and y position with and without the SSD.
Remember, only simulated data are used. The improvement is clearly visible (as expected). To get these pictures for real data, the alignment has to be done.
But up to know Jonathan is doing a very good job and playing with the tracking parameters.
(Click on the picture to enlarge. A new window will open.)


Picture 7: z-coordinate of first hit.	Picture 8: x-coordinate of first hit.	Picture 9: y-coordinate of first hit.

More of Jonathans work can be found Here.

Summary

To sum up we can say, that step by step we manage all parts of our to do list.
Stupidly all progress on the tracking and other parts depends on the alignment,
which has to start again. Luckily all align procedures, codes and kumacs are written.
But the procedure of alignment is very time intensive and we are still outnumbered and short of manpower.

After we got the new processed data (which hopefully look similar for all magnetic fields) we will concentrade on the alignment, and afterwards will tune the tracking parameters. Jonathan knows how to tune the parameters and in the moment I guess, that all procedures and steps we have to take are understood.
It is only a matter of time to go them.

Cu at the collaboration meeting,

your SSD team

Jorg REINNARTH

Last modified: Wed Jul 20 15:46:34 CEST 2005