[PWGCF] Add gain eq to FIT for the long range correlations (#13009)

Author: joachimckh

PWGCF/TwoParticleCorrelations/Tasks/longRangeDihadronCor.cxx

@@ -11,7 +11,7 @@
 
 /// \file longRangeDihadronCor.cxx
 /// \brief long range di-hadron correlation for O-O, Pb-Pb collisions
-/// \author Zhiyong Lu (zhiyong.lu@cern.ch)
+/// \author Zhiyong Lu (zhiyong.lu@cern.ch), Joachim Hansen (joachim.hansen@cern.ch)
 /// \since  Sep/10/2025
 
 #include "PWGCF/Core/CorrelationContainer.h"
@@ -150,15 +150,21 @@ struct LongRangeDihadronCor {
   ConfigurableAxis axisAmplitudeFt0a{"axisAmplitudeFt0a", {5000, 0, 1000}, "FT0A amplitude"};
   ConfigurableAxis axisChannelFt0aAxis{"axisChannelFt0aAxis", {96, 0.0, 96.0}, "FT0A channel"};
 
+  Configurable<std::string> cfgGainEqPath{"cfgGainEqPath", "Analysis/EventPlane/GainEq", "CCDB path for gain equalization constants"};
+  Configurable<int> cfgCorrLevel{"cfgCorrLevel", 1, "calibration step: 0 = no corr, 1 = gain corr"};
+  ConfigurableAxis cfgaxisFITamp{"cfgaxisFITamp", {1000, 0, 5000}, ""};
+  AxisSpec axisFit{cfgaxisFITamp, "fit amplitude"};
+  AxisSpec axisChID = {220, 0, 220};
   // make the filters and cuts.
   Filter collisionFilter = (nabs(aod::collision::posZ) < cfgCutVtxZ);
-  Filter trackFilter = (nabs(aod::track::eta) < cfgCutEta) && (aod::track::pt > cfgCutPtMin) && (aod::track::pt < cfgCutPtMax) && ((requireGlobalTrackInFilter()) || (aod::track::isGlobalTrackSDD == (uint8_t) true)) && (aod::track::tpcChi2NCl < cfgCutChi2prTPCcls) && (nabs(aod::track::dcaZ) < cfgCutDCAz);
+  Filter trackFilter = (nabs(aod::track::eta) < cfgCutEta) && (aod::track::pt > cfgCutPtMin) && (aod::track::pt < cfgCutPtMax) && ((requireGlobalTrackInFilter()) || (aod::track::isGlobalTrackSDD == static_cast<uint8_t>(true))) && (aod::track::tpcChi2NCl < cfgCutChi2prTPCcls) && (nabs(aod::track::dcaZ) < cfgCutDCAz);
   using FilteredCollisions = soa::Filtered<soa::Join<aod::Collisions, aod::EvSel, aod::CentFT0Cs, aod::CentFT0CVariant1s, aod::CentFT0Ms, aod::CentFV0As, aod::Mults>>;
   using FilteredTracks = soa::Filtered<soa::Join<aod::Tracks, aod::TrackSelection, aod::TracksExtra, aod::TracksDCA>>;
 
   // FT0 geometry
   o2::ft0::Geometry ft0Det;
   std::vector<o2::detectors::AlignParam>* offsetFT0;
+  std::vector<float> cstFT0RelGain{};
 
   // Corrections
   TH3D* mEfficiency = nullptr;
@@ -272,6 +278,8 @@ struct LongRangeDihadronCor {
       registry.add("Trig_hist", "", {HistType::kTHnSparseF, {{axisSample, axisVertex, axisPtTrigger}}});
       registry.add("Assoc_amp_same", "", {HistType::kTH2D, {axisChannelFt0aAxis, axisAmplitudeFt0a}});
       registry.add("Assoc_amp_mixed", "", {HistType::kTH2D, {axisChannelFt0aAxis, axisAmplitudeFt0a}});
+      registry.add("FT0Amp", "", {HistType::kTH2F, {axisChID, axisFit}});
+      registry.add("FT0AmpCorr", "", {HistType::kTH2F, {axisChID, axisFit}});
     }
 
     registry.add("eventcount", "bin", {HistType::kTH1F, {{4, 0, 4, "bin"}}}); // histogram to see how many events are in the same and mixed event
@@ -354,6 +362,32 @@ struct LongRangeDihadronCor {
     }
   }
 
+  void loadGain(aod::BCsWithTimestamps::iterator const& bc)
+  {
+    cstFT0RelGain.clear();
+    cstFT0RelGain = {};
+    std::string fullPath;
+
+    auto timestamp = bc.timestamp();
+    constexpr int ChannelsFT0 = 208;
+    if (cfgCorrLevel == 0) {
+      for (auto i{0u}; i < ChannelsFT0; i++) {
+        cstFT0RelGain.push_back(1.);
+      }
+    } else {
+      fullPath = cfgGainEqPath;
+      fullPath += "/FT0";
+      const auto objft0Gain = ccdb->getForTimeStamp<std::vector<float>>(fullPath, timestamp);
+      if (!objft0Gain) {
+        for (auto i{0u}; i < ChannelsFT0; i++) {
+          cstFT0RelGain.push_back(1.);
+        }
+      } else {
+        cstFT0RelGain = *(objft0Gain);
+      }
+    }
+  }
+
   void loadCorrection(uint64_t timestamp)
   {
     if (correctionsLoaded) {
@@ -434,15 +468,21 @@ struct LongRangeDihadronCor {
   void getChannel(TFT0s const& ft0, std::size_t const& iCh, int& id, float& ampl)
   {
     int switchCor = cfgSwitchCor;
+    int rID{0};
     if (switchCor == kFT0C) {
       id = ft0.channelC()[iCh];
+      rID = id + 96;
       ampl = ft0.amplitudeC()[iCh];
     } else if (switchCor == kFT0A) {
       id = ft0.channelA()[iCh];
+      rID = id;
       ampl = ft0.amplitudeA()[iCh];
     } else {
       LOGF(fatal, "Cor Index %d out of range", switchCor);
     }
+    registry.fill(HIST("FT0Amp"), rID, ampl);
+    ampl = ampl / cstFT0RelGain[iCh];
+    registry.fill(HIST("FT0AmpCorr"), rID, ampl);
   }
 
   template <CorrelationContainer::CFStep step, typename TTracks, typename TFT0s>
@@ -613,6 +653,7 @@ struct LongRangeDihadronCor {
     if (!collision.has_foundFT0())
       return;
     loadAlignParam(bc.timestamp());
+    loadGain(bc);
     loadCorrection(bc.timestamp());
     if (!cfgCentTableUnavailable) {
       getCentralityWeight(weightCent, cent);