The Preshower calibration in the 2010 run. (Sobczak, Niess, Monteil)

1. April, 21st, 2010 - Clermont team - Calorimetry meeting The Preshower calibration in the 2010 run. (Sobczak, Niess, Monteil) • Calibrating the Preshower w/ tracks: reminder. • Use any L+D track which extrapolation hits the Prs. • Build the charge distribution for the 6016 channels: • Correcting for the track length as given by the track extrapolation. • Store for further study the kinematical and PID characteristics of the tracks. • Fit a Landau distribution convoluted with a gaussian to the charge distribution. • Use the Most Probable Value (MPV) of the Landau as the estimate of the cell response. PRS timing and calibration

2. April, 21st, 2010 - Clermont team - Calorimetry meeting 1. Calibrating the Preshower w/ tracks: reminder. • One channel in 2010 data for illustration. • Harware corrections: • Within a board, intercalibrate the channels w.r.t to the hottest one. • Then use the hottest MPV within each board to get the relevant HV of the tubes (equalizes boards). • Software correction: just get the 6016 MPV and normalize to the desired value. Currently, 15 ADC counts. PRS timing and calibration

3. April, 21st, 2010 - Clermont team - Calorimetry meeting 2. The calibration w/ 2009 data: • We used tracks found in the few hundred kevents posterior to the 2009 scan to deal with realistic timing conditions (see Krzysztof’s talk 17/02/2010). • Everywhere an improvement in the precision was seen w.r.t the cosmics calibration, the coefficients (so-called numeric gains) were applied in the electronics. Exclude only the y outermost boards. • Simultaneously, HV were tuned using Anatoli’s law: DAC=f(HV). A-side was moved relatively to C-side since we inject there the delays (see Valentin’s talk 17/02/2010). • Expectation: everyone at 20 ADC counts. PRS timing and calibration

4. April, 21st, 2010 - Clermont team - Calorimetry meeting 2. The calibration w/ 2009 data: performance measured w/ 28Mtracks MagDown 2010 data : the observed picture is far from expectation ! Explanation: we messed up HV files and started from the HV settings dealing with the TOTAL CHARGE at 20 ADC counts. The difference in signal shape for the different cell geometries makes the further differences observed per region. PRS timing and calibration

5. April, 21st, 2010 - Clermont team - Calorimetry meeting • Actions: • We diagnosed that with the very first data. Three regional corrective factors per side were measured with the first 300 kevents and set in the CondDb. Thanks to Olivier D. 2010-03-09  ... ].  (local tag : prs-20100407 ) • 9 Mevents MagDown (28 M of useful tracks) were used to compute the MPVs. The corrective factors were set in CondDb since Friday 16/04.SQLDDDB v25r6  (local tag prs_20100414) • Bottomline: if you are processing data with the latter tag (for instance data reprocessed the weekend of 17/04), you’ll find the PreShower with the current best knowledge of its calibration. PRS timing and calibration

6. April, 21st, 2010 - Clermont team - Calorimetry meeting 4. Performance / cross-checks: A-side. PRS timing and calibration

7. April, 21st, 2010 - Clermont team - Calorimetry meeting 4. Performance / cross-checks: C-side. PRS timing and calibration

8. April, 21st, 2010 - Clermont team - Calorimetry meeting 4. Performance / cross-checks: C-side vs A-side in numbers. PRS timing and calibration

9. April, 21st, 2010 - Clermont team - Calorimetry meeting 4. Performance / cross-checks: Comparison MagDown (28 Mtracks) vs MagUp (24 Mtracks). r=0.969 No effect on calibration coefficients. Checked also per region. PRS timing and calibration

10. April, 21st, 2010 - Clermont team - Calorimetry meeting 4. Performance / cross-checks: EF and the 2010 calibration EF sees a smooth calibration coefficients distribution. MPV spread is already lower than EF spread. It gives a first estimate of the achieved precision. Typically better than 6%. Comprehensively exposed in Aurelien’s talk. Performance to be quantified on future tracks. But already confident that we’re close to the target. PRS timing and calibration

11. April, 21st, 2010 - Clermont team - Calorimetry meeting 5. Conclusions: • From Aurelien’s Energy Flow, the current calibration is seen better than the EF intrinsic limit (say < 5 %). We are close to the target. • We stay with these numbers till the ECAL gets calibrated. • Then, we’ll feed the electronics with the updated numeric gains within boards and will modify the PMT HV such that all channels are at 10 ADC counts. • Meanwhile, we’ll complete the refined analysis of the MIP calibration regarding impact of the track length corrections, P and PT dependencies of the corrective factors etc … PRS timing and calibration