From 0ce6748eae75860efd588d6a0844aa03f83734be Mon Sep 17 00:00:00 2001
From: wiechula <Jens.Wiechula@cern.ch>
Date: Thu, 9 Nov 2023 00:54:43 +0100
Subject: [PATCH] Fix TimeGain calibration application: limit to fit range

---
 .../TPC/include/DataFormatsTPC/CalibdEdxCorrection.h      | 8 +++++++-
 .../TPC/calibration/include/TPCCalibration/CalibdEdx.h    | 7 +++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/DataFormats/Detectors/TPC/include/DataFormatsTPC/CalibdEdxCorrection.h b/DataFormats/Detectors/TPC/include/DataFormatsTPC/CalibdEdxCorrection.h
index eb9fd33c27476..4225faf8437c4 100644
--- a/DataFormats/Detectors/TPC/include/DataFormatsTPC/CalibdEdxCorrection.h
+++ b/DataFormats/Detectors/TPC/include/DataFormatsTPC/CalibdEdxCorrection.h
@@ -30,6 +30,11 @@
 namespace o2::tpc
 {
 
+namespace conf_dedx_corr
+{
+GPUconstexpr() float TglScale[4] = {1.9, 1.5, 1.22, 1.02}; ///< Max Tgl values for each ROC type
+}
+
 class CalibdEdxCorrection
 {
  public:
@@ -54,7 +59,8 @@ class CalibdEdxCorrection
       return 1;
     }
 
-    tgl = o2::gpu::CAMath::Abs(tgl);
+    // limit to the fit range in the respective region
+    tgl = o2::gpu::CAMath::Min(conf_dedx_corr::TglScale[stack.type], o2::gpu::CAMath::Abs(tgl));
     auto p = mParams[stackIndex(stack, charge)];
     float result = p[0];
     // Tgl part
diff --git a/Detectors/TPC/calibration/include/TPCCalibration/CalibdEdx.h b/Detectors/TPC/calibration/include/TPCCalibration/CalibdEdx.h
index 54b9d6f98ee35..b07d00c132175 100644
--- a/Detectors/TPC/calibration/include/TPCCalibration/CalibdEdx.h
+++ b/Detectors/TPC/calibration/include/TPCCalibration/CalibdEdx.h
@@ -136,11 +136,10 @@ class CalibdEdx
   /// Save the histograms to a TTree.
   void writeTTree(std::string_view fileName) const;
 
-  constexpr static float MipScale = 1.0 / 50.0;                         ///< Inverse of target dE/dx value for MIPs
-  constexpr static std::array<float, 4> TglScale{1.9, 1.5, 1.22, 1.02}; ///< Max Tgl values for each ROC type
+  constexpr static float MipScale = 1.0 / 50.0; ///< Inverse of target dE/dx value for MIPs
 
-  constexpr static float scaleTgl(float tgl, GEMstack roc) { return tgl / CalibdEdx::TglScale[roc]; }
-  constexpr static float recoverTgl(float scaledTgl, GEMstack roc) { return scaledTgl * CalibdEdx::TglScale[roc]; }
+  constexpr static float scaleTgl(float tgl, GEMstack rocType) { return tgl / conf_dedx_corr::TglScale[rocType]; }
+  constexpr static float recoverTgl(float scaledTgl, GEMstack rocType) { return scaledTgl * conf_dedx_corr::TglScale[rocType]; }
 
  private:
   bool mFitSnp{};