# Presentation: 196442

## Correcting the energy sharing problem

- Jan Stark, LPSC Grenoble

- CAT Force meeting, May 27th, 2003

- Many thanks to Dean Schamberger, Robert Zitoun and
- Gregorio Bernardi for all their help.

## The energy sharing problem

- One of the BLS boards in a backplane was not letting go of
- the analog bus when it should.
-  charge (energy) read from this particular board is fine
-  for the other boards on the backplane we see the average
-      of their own charge and the charge of the bad board
- Six bad boards in total (not all during exactly the same time).
- This means:
-  if charge in bad board (and no charge in the other boards)
-    see seven more boards with half the energy of the
-        bad board
-  if charge in one of the other boards (and none in the bad
-   board)
-    see only half of the “real” energy in the other board

- Same event as above, but energy rather than
- transverse energy is shown.

- eta bin

- phi bin

- The worst bad boards affect data taken from February to April.

- CATF, May 27, 2003

- Jan Stark

## Strategy for the correction

- We know which boards were bad during which period of time (which runs)
- 	 can invert charge averaging.
- To do this for a given event, we need to know the raw number of ADC counts and the gain path
- for each of the affected cells.
- This information is available in the RAW data files. A good place to apply the correction is
- therefore d0reco running over RAW data files.
- But reprocessing RAW data is a heavy burden. It is desirable to have code that applies the
- correction at DST or TMB level.
- Inconveniences of DST/TMB:
-  gain information is not available
-  less information on very low energy cells than in RAW files (offline zero-suppression)
-  finite precision on number of ADC counts due to packing
- Correction at DST/TMB level requires some approximations
- 	 correction less accurate, but still possible.
- Two versions of the correction code have been written; one that works at RAW level, and another
- one that works at DST/TMB level. Will first show some results obtained with RAW data, and then
- discuss differences RAW  DST/TMB.

- CATF, May 27, 2003

- Jan Stark

## A corrected event

- Before correction:

- After correction:

- CATF, May 27, 2003

- Jan Stark

## A corrected event (continued)

- Different views of the same event (after correction):

- CATF, May 27, 2003

- Jan Stark

## Another (more typical) event

- Events where a bad board has a lot of energy look spectacular, but are rare. More abundant
- are events where one of the other boards has energy.

- Tower energy (GeV)
- before correction

- Tower energy (GeV)
- after correction

- Tower energy difference
- | before – after |    (GeV)

- Note the different energy scales.

- CATF, May 27, 2003

- Jan Stark

## DST/TMB vs. RAW

- zoom

- log scale

- GeV

- GeV

- The effects of the inconveniences of DST/TMB can be
- seen in these plots:
-  gain information is not available (need to guess gain)
-        leads to very rare outliers
-  less information on very low energy cells than
-  in RAW files (offline zero-suppression)
-        dominant effect
-  finite precision on ADC counts due to packing
-                very small effect

- Take 300 events from run 175054 and correct the
- shared energy problem, once at RAW level and once
- at TMB level. Compare the cell energies obtained with
- the two different versions of the correction.
- The plots on the right show the difference
-   [cell energy after TMB correction]
-         -  [cell energy after RAW correction]
- for all corrected cells.

- outlier due to wrong
- guess of gain

- either the cell itself, or its
- friend on the bad board is
- killed by the offline zero
- suppression

- CATF, May 27, 2003

- Jan Stark

## Impact on missing ET

- To estimate the impact of the shared energy problem on missing ET, plot distribution of missing ET for the
- first 51k events of run 175054 before and after the correction.

- BTW: these plots have been made using the thumbnail version of the correction.

- log scale

- log scale

- log scale

- GeV

- GeV

- GeV

- missing ET before correction

- missing ET after correction

- difference
- after - before

- CATF, May 27, 2003

- Jan Stark

## Conclusion

- Implemented code to correct the shared energy problem in data.
- Two versions of the code are available:
-   -  one that works on RAW data
- 	Correction integrated into d0reco.
- 	Available in CVS and included in the latest build of p14.03 .
-   -  and one that works on DST and TMB+ (thumbnails that include the CalDataChunk)
- 	Correction implemented as framework module.
- 	Can be added to analysis executables that run in post-processing mode
- 	(i.e. that re-reconstruct EM-candidates, jets, etc. from the CalDataChunk).
- 	This code will be committed to CVS today (requires some changes in
- 	cal_nlc package).
- 	The correction at DST/TMB level is less precise than the correction on RAW data.

- CATF, May 27, 2003

- Jan Stark