[PWGJE,EMCAL-568] Add option to use energy calibration done with old cell format

- The Pi0 was observed to be wider when using 2024 data. This might be introduced with the energy calibration usign the new cell format
- In this PR, an option to correct the cell energy by dividing with the new and multiplying with the old gain calib is introduced
- Option is off by default

Author: jokonig

PWGJE/TableProducer/emcalCorrectionTask.cxx

@@ -35,6 +35,7 @@
 #include "EMCALBase/ClusterFactory.h"
 #include "EMCALBase/Geometry.h"
 #include "EMCALBase/NonlinearityHandler.h"
+#include "EMCALCalib/GainCalibrationFactors.h"
 #include "EMCALCalibration/EMCALTempCalibExtractor.h"
 #include "EMCALReconstruction/Clusterizer.h"
 #include "Framework/ASoA.h"
@@ -118,6 +119,7 @@ struct EmcalCorrectionTask {
   Configurable<std::string> pathTempCalibCCDB{"pathTempCalibCCDB", "Users/j/jokonig/EMCalTempCalibParams", "Path in the ccdb where slope and intercept for each cell are stored"}; // change to official path as soon as it is available
   Configurable<bool> useTempCalibMean{"useTempCalibMean", false, "Switch to turn on Temperature mean calculation instead of median."};
   Configurable<float> mcCellEnergyResolutionBroadening{"mcCellEnergyResolutionBroadening", 0., "Relative widening of the MC cell energy resolution. 0 for no widening, 0.1 for 10% widening, etc. Only applied to MC."};
+  Configurable<bool> applyGainCalibShift{"applyGainCalibShift", false, "Apply shift for cell gain calibration to use values before cell format change (Sept. 2023)"};
 
   // Require EMCAL cells (CALO type 1)
   Filter emccellfilter = aod::calo::caloType == selectedCellType;
@@ -151,6 +153,9 @@ struct EmcalCorrectionTask {
   std::unique_ptr<o2::emcal::EMCALTempCalibExtractor> mTempCalibExtractor;
   bool mIsTempCalibInitialized = false;
 
+  // Gain calibration
+  std::array<float, 17664> mArrGainCalibDiff;
+
   std::vector<std::pair<int, int>> mExtraTimeShiftRunRanges;
 
   // Current run number
@@ -184,6 +189,11 @@ struct EmcalCorrectionTask {
       mTempCalibExtractor = std::make_unique<o2::emcal::EMCALTempCalibExtractor>();
     }
 
+    // gain calibration shift initialization
+    if (applyGainCalibShift) {
+      initializeGainCalibShift();
+    }
+
     // read all the cluster definitions specified in the options
     if (clusterDefinitions->length()) {
       std::stringstream parser(clusterDefinitions.value);
@@ -361,6 +371,9 @@ struct EmcalCorrectionTask {
         if (applyCellAbsScale) {
           amplitude *= getAbsCellScale(cell.cellNumber());
         }
+        if (applyGainCalibShift) {
+          amplitude *= mArrGainCalibDiff[cell.cellNumber()];
+        }
         if (applyTempCalib) {
           amplitude *= mTempCalibExtractor->getGainCalibFactor(static_cast<uint16_t>(cell.cellNumber()));
         }
@@ -611,6 +624,9 @@ struct EmcalCorrectionTask {
         if (static_cast<bool>(hasShaperCorrection) && emcal::intToChannelType(cell.cellType()) == emcal::ChannelType_t::LOW_GAIN) { // Apply shaper correction to LG cells
           amplitude = o2::emcal::NonlinearityHandler::evaluateShaperCorrectionCellEnergy(amplitude);
         }
+        if (applyGainCalibShift) {
+          amplitude *= mArrGainCalibDiff[cell.cellNumber()];
+        }
         if (applyTempCalib) {
           amplitude *= mTempCalibExtractor->getGainCalibFactor(static_cast<uint16_t>(cell.cellNumber()));
         }
@@ -1013,6 +1029,18 @@ struct EmcalCorrectionTask {
     }
     return timeshift + timesmear;
   };
+
+  void initializeGainCalibShift()
+  {
+    auto& ccdbMgr = o2::ccdb::BasicCCDBManager::instance();
+    uint64_t tsOld = 1634853602000; // timestamp corresponding to LHC22o old gain calib object
+    o2::emcal::GainCalibrationFactors* paramsOld = ccdbMgr.getForTimeStamp<o2::emcal::GainCalibrationFactors>("EMC/Calib/GainCalibFactors", tsOld);
+    uint64_t tsNew = 1734853602000; // timestamp corresponding to new gain calib object (new cell compression)
+    o2::emcal::GainCalibrationFactors* paramsNew = ccdbMgr.getForTimeStamp<o2::emcal::GainCalibrationFactors>("EMC/Calib/GainCalibFactors", tsNew);
+    for (uint16_t i = 0; i < mArrGainCalibDiff.size(); ++i) {
+      mArrGainCalibDiff[i] = paramsOld->getGainCalibFactors(i) == 0 ? 1. : paramsNew->getGainCalibFactors(i) / paramsOld->getGainCalibFactors(i);
+    }
+  }
 };
 
 WorkflowSpec defineDataProcessing(ConfigContext const& cfgc)