1. Correcting the energy sharing problem Jan Stark, LPSC Grenoble CAT Force meeting, May 27 th, 2003 Many thanks to Dean Schamberger, Robert Zitoun and Gregorio Bernardi for all their help.

2. Jan StarkCATF, May 27, 20032 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.

3. Jan StarkCATF, May 27, 20033 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.

4. Jan StarkCATF, May 27, 20034 A corrected event Before correction: After correction:

5. Jan StarkCATF, May 27, 20035 A corrected event (continued) Different views of the same event (after correction):

6. Jan StarkCATF, May 27, 20036 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. eta bin phi bin Tower energy (GeV) before correction eta bin phi bin eta bin phi bin Tower energy (GeV) after correction Tower energy difference | before – after | (GeV) Note the different energy scales.

7. Jan StarkCATF, May 27, 20037 DST/TMB vs. RAW zoom log scale 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

8. Jan StarkCATF, May 27, 20038 Impact on missing E T To estimate the impact of the shared energy problem on missing E T, plot distribution of missing E T 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 GeV missing E T before correction missing E T after correction difference after - before

9. Jan StarkCATF, May 27, 20039 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.