# Presentation: 196454

## Calorimeter calibration

- Short description of readout and calibration
- Linearity ramp    gains
- Non linearity (SCA, pulser)
- Correction of non linearity
- Resolution on Z peak

- Robert ZitounSUNY Stony Brook and LAPP

- All D0 MeetingFebruary 22, 2002

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## 

preamp matching the cell capacitance + shaper
2 gains in the ratio 18
2 analog memories (SCA) to wait for level 1
BLS to subtract the baseline (3 ticks earlier)
another SCA to wait for level 2
12 bits ADC (1 ADC count ~ 5 MeV)
Gain selector (forced 8, forced 1, normal)Multiplies ADC counts by 8 in 1 mode so that same input signal gives same output

Calibration needed to accurately measure gains in both modes a8 and a1 (g = a8/a1~1 defined by precision resistors)

- preamp matching the cell capacitance + shaper
- 2 gains in the ratio 18
- 2 analog memories (SCA) to wait for level 1
- BLS to subtract the baseline (3 ticks earlier)
- another SCA to wait for level 2
- 12 bits ADC (1 ADC count ~ 5 MeV)
- Gain selector (forced 8, forced 1, normal)Multiplies ADC counts by 8 in 1 mode so that same input signal gives same output
- Calibration needed to accurately measure gains in both modes a8 and a1 (g = a8/a1~1 defined by precision resistors)

**Readout chain**

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Calibration

- Current generator driven by a (pair of) DAC
- Inductance (1mH) loaded by the current
- On a command signal, a switch disrupts the current to the inductance
- Inductance unloads into a resistor and produces an exponential signal towards the preamplifiers

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Linearity ramps

- Send (not so well ) known calibration pulses
- Increase DAC setting from zero to saturation(1 DAC unit ~ 1 MeV)
- Forced 8 and 1 modes
- Fit slopes  *a*8 and *a*1 (or                 )

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Linearity ramps (2)

- Dispersion     ~5% in em           ~10% in had

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Slope correction to Z  ee events

- Present reco_analyze versions:single slope for all cells/gain in 			 resolution worsened
- Use rootuple files from Marco’s NewStream
- redo Scone clustering
- apply cell by cell slope correction
- Absolute DAC/GeV normalization not (yet) available		 Trimmed so that Z peak at the same place as without correction
- Event selection
- require 2 certified (iso, emf, HMx9) clusters in CC (|*z*3|<110cm)
- reject clusters in cracks
- pT1, pT2>20 GeV

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## pT1, pT2>20 GeV         	      pT1, pT2>30 GeV 				      back to back

**Slope correction to Z ******** ee events (2)**

- raw data

- +  energy correction (Sabine Crépé)

- slope +  corrections

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Residuals from a line (ax+b)

below 10 ADC counts (<0.3%) above ~2 GeV
non linearity same for all channels
 8 and  1 gain residuals scale
Intercept b non zero ~ 50 ADC counts

- below 10 ADC counts (<0.3%) above ~2 GeV
- non linearity same for all channels
-  8 and  1 gain residuals scale
- Intercept b non zero ~ 50 ADC counts

**Non linearity**

- Pulser or Readout ?

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Take 2 runs
forced 8 with DAC = 0,   200,   400, ...
forced 1 with DAC = 0, 1600, 3200,...

Linear pulsers  same charge in SCA  same count number after conversion

Scaling implies non linear readout
Traced down to SCA chip 

- forced 8 with DAC = 0,   200,   400, ...
- forced 1 with DAC = 0, 1600, 3200,...
- Linear pulsers  same charge in SCA  same count number after conversion
- Scaling implies non linear readout
- Traced down to SCA chip

**SCA non linearity**

- However ...

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Pulser non linearity

- Low DAC broken scaling  pulsers not linear
- Non linearity traced down to DAC component
- Final model
- SCA gain  1
- SCA gain  8
- DAC
- unique **  for ~50,000 channels
- different **  for each channel (not going to reco)

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Final residuals

- ADC to energy conversion with
- universal function for SCA non linearity
- 2 gains a8 and a1 (or a8 and g = a8/a1)
- Residuals better than 10 ADC counts on the whole range for both gains

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## What if not corrected?

- Energy biased towards lower value
- 2.0 GeV pulse  ~ 400 ADC counts
- reco_analyze ~ 400 /0.25 = 1.7 GeV

- ~300 MeV underestimation

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Channel energy correction

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## Calibration correction to Zee events

**Calibration correction to Z********ee events**

- No calibcorrection
- with calibcorrection(slopes +non linearity)
- Do not take resolutions too seriously:
- large statistical fluctuations (commercial plots)
- Breit-Wigner of width 2.5 GeV should give  ~ 3.0 GeV

- M = 85.0 GeV
-  = 3.0 GeV

- M = 91.8 GeV
-  = 2.0 GeV

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)

## To do

- Timing corrections
- physics pulses   20 ns   0.3% on signal  (Mingchen Gao)
- calib pulses: up to  1%. May cancel with previous (S. Beauceron, U. Bassler)
- Correction factor from calibration to physics pulses (P. Pétroff et (L)al.)
- Calibration pulses bounce back from the detector mostly for hadronic channels	 some more work to certify
- Non linearity correction to be implemented soon
- Slopes correction need database (flat file?)

- R. Zitoun, Stony Brook and LAPP (http://www-d0.fnal.gov/~zitoun)