[ALICE3] TRK/FT3 digitizer: noise rate set in hits/px/s instead of hits/px/ROF + uniform ToA within ROF for noise digits

Author: atriolo

Detectors/Upgrades/ALICE3/TRKFT3/common/simulation/include/TRKFT3Simulation/ChipDigitsContainer.h

@@ -46,7 +46,7 @@ class ChipDigitsContainer
   o2::trkft3::PreDigit* findDigit(ULong64_t key);
   void addDigit(ULong64_t key, UInt_t roframe, UShort_t row, UShort_t col, int charge, o2::MCCompLabel lbl, float toa = 0.f);
   template <int DetID>
-  void addNoise(UInt_t rofMin, UInt_t rofMax, const o2::trkft3::DigiParams<DetID>* params, int subDetID, int layer);
+  void addNoise(UInt_t rofMin, UInt_t rofMax, const o2::trkft3::DigiParams<DetID>* params, int subDetID, int layer, float rofLengthNS);
 
   /// Get global ordering key made of readout frame, column and row
   static ULong64_t getOrderingKey(UInt_t roframe, UShort_t row, UShort_t col)
@@ -85,7 +85,7 @@ inline void ChipDigitsContainer::addDigit(ULong64_t key, UInt_t roframe, UShort_
 } // namespace o2::trkft3
 
 template <int DetID>
-void o2::trkft3::ChipDigitsContainer::addNoise(UInt_t rofMin, UInt_t rofMax, const o2::trkft3::DigiParams<DetID>* params, int subDetID, int layer)
+void o2::trkft3::ChipDigitsContainer::addNoise(UInt_t rofMin, UInt_t rofMax, const o2::trkft3::DigiParams<DetID>* params, int subDetID, int layer, float rofLengthNS)
 {
   UInt_t row = 0;
   UInt_t col = 0;
@@ -102,7 +102,7 @@ void o2::trkft3::ChipDigitsContainer::addNoise(UInt_t rofMin, UInt_t rofMax, con
     maxRows = o2::trk::constants::moduleMLOT::chip::nRows;
     maxCols = o2::trk::constants::moduleMLOT::chip::nCols;
   }
-  mean = params->getNoisePerPixel() * maxRows * maxCols;
+  mean = params->getNoisePerPixel() * rofLengthNS * 1e-9 * maxRows * maxCols; // hits per ROF in the chip, calculated from the noise rate in hits/s
   nel = static_cast<int>(params->getChargeThreshold() * 1.1);
 
   LOG(debug) << "Adding noise for chip " << mChipIndex << " with mean " << mean << " and charge " << nel;
@@ -121,7 +121,8 @@ void o2::trkft3::ChipDigitsContainer::addNoise(UInt_t rofMin, UInt_t rofMax, con
       }
       auto key = getOrderingKey(rof, row, col);
       if (!findDigit(key)) {
-        addDigit(key, rof, row, col, nel, o2::MCCompLabel(true), 0.f); /// TODO: find a better ToA for noise
+        float toa = gRandom->Uniform(0.f, rofLengthNS); // noise fires uniformly in the ROF
+        addDigit(key, rof, row, col, nel, o2::MCCompLabel(true), toa);
       }
     }
   }

Detectors/Upgrades/ALICE3/TRKFT3/common/simulation/include/TRKFT3Simulation/DPLDigitizerParam.h

@@ -31,7 +31,7 @@ struct DPLDigitizerParam : public o2::conf::ConfigurableParamHelper<DPLDigitizer
   }
 
   bool continuous = true;                   ///< flag for continuous simulation
-  float noisePerPixel = DEFNoisePerPixel(); ///< ALPIDE Noise per channel
+  float noisePerPixel = DEFNoisePerPixel(); ///< ALMIRA chips noise rate in hits/pixel/s
   float strobeFlatTop = 20.;                ///< strobe shape flat top
   float strobeMaxRiseTime = 0.;             ///< strobe max rise time
   float strobeQRiseTime0 = 0.;              ///< q @ which strobe rise time is 0
@@ -54,7 +54,7 @@ struct DPLDigitizerParam : public o2::conf::ConfigurableParamHelper<DPLDigitizer
  private:
   static constexpr float DEFNoisePerPixel()
   {
-    return N == o2::detectors::DetID::TRK ? 1e-7 : 1e-8; // ITS/MFT values here!!
+    return N == o2::detectors::DetID::TRK ? 0.2 : 0.2; // TRK/FT3 values here. At the moment the noise should be the same for both cases, but option to set it differently left for the future
   }
 
   static constexpr std::string_view ParamName[2] = {"TRKDigitizerParam", "FT3DigitizerParam"};

Detectors/Upgrades/ALICE3/TRKFT3/common/simulation/include/TRKFT3Simulation/DigiParams.h

@@ -124,7 +124,7 @@ class DigiParams
 
  private:
   static constexpr double infTime = 1e99;
-  float mNoisePerPixel = 1.e-7;          ///< Noise per chip
+  float mNoisePerPixel = 0.2;            ///< noise rate per pixel, in hits/s
   double mTimeOffset = -2 * infTime;     ///< time offset (in seconds!) to calculate ROFrame from hit time
   int mChargeThreshold = 75;             ///< charge threshold in Nelectrons
   int mMinChargeToAccount = 7;           ///< minimum charge contribution to account

Detectors/Upgrades/ALICE3/TRKFT3/common/simulation/src/DigiParams.cxx

@@ -68,7 +68,7 @@ void DigiParams<DetIDV>::print() const
   printf("Min N electrons to account     : %d\n", mMinChargeToAccount);
   printf("Number of charge sharing steps : %d\n", mNSimSteps);
   printf("ELoss to N electrons factor    : %e\n", mEnergyToNElectrons);
-  printf("Noise level per pixel          : %e\n", mNoisePerPixel);
+  printf("Noise rate per pixel           : %e/s\n", mNoisePerPixel);
   printf("Charge time-response:\n");
   mSignalShape.print();
 }

Detectors/Upgrades/ALICE3/TRKFT3/common/simulation/src/Digitizer.cxx

@@ -153,7 +153,7 @@ void Digitizer<DetID>::process(const std::vector<Hit>* hits, int evID, int srcID
 template <int DetID>
 void Digitizer<DetID>::setEventTime(const o2::InteractionTimeRecord& irt, int layer)
 {
-  LOG(info) << "Setting event time to " << irt.getTimeNS() << " ns after orbit 0 bc 0";
+  LOG(debug) << "Setting event time to " << irt.getTimeNS() << " ns after orbit 0 bc 0";
   // assign event time in ns
   mEventTime = irt;
   // RO frame corresponding to provided time
@@ -213,7 +213,7 @@ void Digitizer<DetID>::fillOutputContainer(uint32_t frameLast, int layer)
       if (chip.isDisabled() || (layer >= 0 && getROFLayer(chip.getChipIndex()) != layer)) {
         continue;
       }
-      chip.addNoise(mROFrameMin, mROFrameMin, &mParams, mGeometry->getSubDetID(chip.getChipIndex()), mGeometry->getLayer(chip.getChipIndex())); /// TODO: add noise
+      chip.addNoise(mROFrameMin, mROFrameMin, &mParams, mGeometry->getSubDetID(chip.getChipIndex()), mGeometry->getLayer(chip.getChipIndex()), mParams.getROFrameLength(getROFLayer(chip.getChipIndex())));
       auto& buffer = chip.getPreDigits();
       if (buffer.empty()) {
         continue;

Steer/DigitizerWorkflow/src/TRKDigitizerSpec.cxx

@@ -303,7 +303,7 @@ class TRKFT3DPLDigitizerTask : BaseDPLDigitizer
       // parameters of signal time response: flat-top duration, max rise time and q @ which rise time is 0
       digipar.getSignalShape().setParameters(dopt.strobeFlatTop, dopt.strobeMaxRiseTime, dopt.strobeQRiseTime0);
       digipar.setChargeThreshold(dopt.chargeThreshold); // charge threshold in electrons
-      digipar.setNoisePerPixel(dopt.noisePerPixel);     // noise level
+      digipar.setNoisePerPixel(dopt.noisePerPixel);     // noise rate in hits/pixel/s
       digipar.setTimeOffset(dopt.timeOffset);
       digipar.setNSimSteps(dopt.nSimSteps);