TPC SCD: TrackResiduals y/x grid edge from the pad plane

Detectors/TPC/calibration/SpacePoints/include/SpacePoints/TrackResiduals.h

@@ -460,7 +460,6 @@ class TrackResiduals
 
   // some constants
   static constexpr float sFloatEps{1.e-7f}; ///< float epsilon for robust linear fitting
-  static constexpr float sDeadZone{1.5f};   ///< dead zone for TPC in between sectors
   static constexpr int sSmtLinDim{4};       ///< max matrix size for smoothing (pol1)
   static constexpr int sMaxSmtDim{7};       ///< max matrix size for smoothing (pol2)
 
@@ -483,7 +482,7 @@ class TrackResiduals
   int mNVoxPerSector{};                                    ///< number of voxels per sector
   float mDX{};                                             ///< x bin size
   float mDXI{};                                            ///< inverse of x bin size
-  std::vector<float> mMaxY2X{};                            ///< max y/x at each x bin, accounting dead zones
+  std::vector<float> mMaxY2X{};                            ///< max y/x at each x bin: the pad plane's edge in its pad row
   std::vector<float> mDY2X{};                              ///< y/x bin size at given x bin
   std::vector<float> mDY2XI{};                             ///< inverse y/x bin size at given x bin
   std::vector<float> mY2XBinsDH{};                         ///< half width in y/x within the interval [-1..1]

Detectors/TPC/calibration/SpacePoints/src/TrackResiduals.cxx

@@ -17,6 +17,7 @@
 ///
 
 #include "SpacePoints/TrackResiduals.h"
+#include "TPCBase/Mapper.h"
 #include "CommonConstants/MathConstants.h"
 #include "ReconstructionDataFormats/Track.h"
 #include "MathUtils/fit.h"
@@ -164,14 +165,21 @@ void TrackResiduals::initBinning()
     mDXI = 1.f / mDX; // should not be used
   }
   //
-  // Y/X binning
+  // Y/X binning: y/x = +-mMaxY2X is the pad plane's edge in the pad row of the x bin (the outer edge of its outermost pads; with uniform
+  // X-binning the pad row closest to the bin centre), so the outermost y/x bins end with the row's last pads
   mMaxY2X.resize(mNXBins);
   mDY2XI.resize(mNXBins);
   mDY2X.resize(mNXBins);
   //
+  const auto& mapper = Mapper::instance();
   for (int ix = 0; ix < mNXBins; ++ix) {
     float x = getX(ix);
-    mMaxY2X[ix] = tan(.5f * SECPHIWIDTH) - sDeadZone / x;
+    int row = ix;
+    if (mUniformBins[VoxX]) {
+      row = int(std::min_element(param::RowX, param::RowX + param::NPadRows, [x](float a, float b) { return std::abs(a - x) < std::abs(b - x); }) - param::RowX);
+    }
+    const float halfWidth = 0.5f * mapper.getNumberOfPadsInRowSector(row) * mapper.getPadRegionInfo(Mapper::REGION[row]).getPadWidth();
+    mMaxY2X[ix] = halfWidth / x;
     mDY2XI[ix] = mNY2XBins / (2.f * mMaxY2X[ix]);
     mDY2X[ix] = 1.f / mDY2XI[ix];
   }

Detectors/TPC/calibration/SpacePoints/test/testTrackResiduals.cxx

@@ -19,6 +19,7 @@
 #define BOOST_TEST_DYN_LINK
 #include <boost/test/unit_test.hpp>
 #include "SpacePoints/TrackResiduals.h"
+#include "TPCBase/Mapper.h"
 
 namespace o2::tpc
 {
@@ -58,4 +59,16 @@ BOOST_AUTO_TEST_CASE(TrackResidualsBinning_test)
   }
 }
 
+// the y/x grid ends at the pad plane's edge of each pad row
+BOOST_AUTO_TEST_CASE(TrackResidualsY2XEdge_test)
+{
+  TrackResiduals resid;
+  resid.initBinning();
+  const auto& mapper = Mapper::instance();
+  for (int ix = 0; ix < resid.getNXBins(); ++ix) {
+    const float halfWidth = 0.5f * mapper.getNumberOfPadsInRowSector(ix) * mapper.getPadRegionInfo(Mapper::REGION[ix]).getPadWidth();
+    BOOST_CHECK_CLOSE(resid.getMaxY2X(ix) * resid.getX(ix), halfWidth, 1e-3);
+  }
+}
+
 } // namespace o2::tpc