ITS3: remove unnecessary recalculation of trackingframe

Signed-off-by: Felix Schlepper <[email protected]>

Author: f3sch

Detectors/ITSMFT/ITS/base/include/ITSBase/GeometryTGeo.h

@@ -333,9 +333,6 @@ class GeometryTGeo : public o2::itsmft::GeometryTGeo
   /// Sym name of the chip in the given layer/halfbarrel/stave/substave/module
   static const char* composeSymNameChip(int lr, int hba, int sta, int ssta, int mod, int chip, bool isITS3 = false);
 
-  // create matrix for transformation from tracking frame to local one for ITS3
-  const Mat3D getT2LMatrixITS3(int isn, float alpha);
-
   TString getMatrixPath(int index) const;
 
   /// Get the transformation matrix of the SENSOR (not necessary the same as the chip)

Detectors/ITSMFT/ITS/base/src/GeometryTGeo.cxx

@@ -899,19 +899,6 @@ TGeoHMatrix& GeometryTGeo::createT2LMatrix(int isn)
   return t2l;
 }
 
-//__________________________________________________________________________
-const o2::math_utils::Transform3D GeometryTGeo::getT2LMatrixITS3(int isn, float alpha)
-{
-  // create for sensor isn the TGeo matrix for Tracking to Local frame transformations with correction for effective thickness
-  static TGeoHMatrix t2l;
-  t2l.Clear();
-  t2l.RotateZ(alpha * RadToDeg()); // rotate in direction of normal to the tangent to the cylinder
-  const TGeoHMatrix& matL2G = getMatrixL2G(isn);
-  const auto& matL2Gi = matL2G.Inverse();
-  t2l.MultiplyLeft(&matL2Gi);
-  return Mat3D(t2l);
-}
-
 //__________________________________________________________________________
 int GeometryTGeo::extractVolumeCopy(const char* name, const char* prefix) const
 {

Detectors/Upgrades/ITS3/macros/align/CheckResidualsITS3.C

@@ -66,16 +66,11 @@ std::optional<Cluster> propagateTo(Track& trk, const o2::itsmft::CompClusterExt&
   ++cTotal;
   auto chipID = clus.getSensorID();
   float sigmaY2{0}, sigmaZ2{0}, sigmaYZ{0};
+  auto isITS3 = o2::its3::constants::detID::isDetITS3(chipID);
   const float alpha = o2::its::GeometryTGeo::Instance()->getSensorRefAlpha(clus.getSensorID());   // alpha for the tracking frame
   const auto locC = o2::its3::ioutils::extractClusterData(clus, pattIt, mDict, sigmaY2, sigmaZ2); // get cluster in sensor local frame with errors
-  Point3D trkC;
-  auto isITS3 = o2::its3::constants::detID::isDetITS3(chipID);
-  if (isITS3) {
-    trkC = o2::its::GeometryTGeo::Instance()->getT2LMatrixITS3(chipID, alpha) ^ (locC); // cluster position in the tracking frame
-  } else {
-    trkC = o2::its::GeometryTGeo::Instance()->getMatrixT2L(chipID) ^ (locC); // cluster position in the tracking frame
-  }
-  const auto gloC = o2::its::GeometryTGeo::Instance()->getMatrixL2G(chipID)(locC); // global cluster position
+  Point3D trkC = o2::its::GeometryTGeo::Instance()->getMatrixT2L(chipID) ^ (locC);                // cluster position in the tracking frame
+  const auto gloC = o2::its::GeometryTGeo::Instance()->getMatrixL2G(chipID)(locC);                // global cluster position
   const auto bz = o2::base::Propagator::Instance()->getNominalBz();
 
   // rotate the parameters to the tracking frame then propagate to the clusters'x

Detectors/Upgrades/ITS3/reconstruction/src/IOUtils.cxx

@@ -48,8 +48,7 @@ void convertCompactClusters(gsl::span<const itsmft::CompClusterExt> clusters,
     float sigmaY2, sigmaZ2, sigmaYZ = 0;
     auto locXYZ = extractClusterData(c, pattIt, dict, sigmaY2, sigmaZ2);
     const auto detID = c.getSensorID();
-    auto& cl3d = output.emplace_back(detID,
-                                     (its3::constants::detID::isDetITS3(detID) ? geom->getT2LMatrixITS3(detID, geom->getSensorRefAlpha(detID)) : geom->getMatrixT2L(detID)) ^ locXYZ); // local --> tracking
+    auto& cl3d = output.emplace_back(detID, geom->getMatrixT2L(detID) ^ locXYZ); // local --> tracking
     if (applyMisalignment) {
       auto lrID = geom->getLayer(detID);
       sigmaY2 += conf.sysErrY2[lrID];
@@ -79,7 +78,6 @@ int loadROFrameDataITS3(its::TimeFrame<7>* tf,
     for (int clusterId{rof.getFirstEntry()}; clusterId < rof.getFirstEntry() + rof.getNEntries(); ++clusterId) {
       auto& c = clusters[clusterId];
       auto sensorID = c.getSensorID();
-      auto isITS3 = its3::constants::detID::isDetITS3(sensorID);
       auto layer = geom->getLayer(sensorID);
 
       float sigmaY2{0}, sigmaZ2{0}, sigmaYZ{0};
@@ -90,16 +88,11 @@ int loadROFrameDataITS3(its::TimeFrame<7>* tf,
       // Transformation to the local --> global
       auto gloXYZ = geom->getMatrixL2G(sensorID) * locXYZ;
 
-      // for cylindrical layers we have a different alpha for each cluster, for regular silicon detectors instead a single alpha for the whole sensor
+      // Inverse transformation to the local --> tracking
+      o2::math_utils::Point3D<float> trkXYZ = geom->getMatrixT2L(sensorID) ^ locXYZ;
+
+      // Tracking alpha angle
       float alpha = geom->getSensorRefAlpha(sensorID);
-      o2::math_utils::Point3D<float> trkXYZ;
-      if (isITS3) {
-        // Inverse transformation to the local --> tracking
-        trkXYZ = geom->getT2LMatrixITS3(sensorID, alpha) ^ locXYZ;
-      } else {
-        // Inverse transformation to the local --> tracking
-        trkXYZ = geom->getMatrixT2L(sensorID) ^ locXYZ;
-      }
 
       tf->addTrackingFrameInfoToLayer(layer, gloXYZ.x(), gloXYZ.y(), gloXYZ.z(), trkXYZ.x(), alpha,
                                       std::array<float, 2>{trkXYZ.y(), trkXYZ.z()},