feat: Add path length branch to RootTrajectoryStatesWriter (#932)

This adds the path length branch to RootTrajectoryStatesWriter. Motivation is to calculate the theoretical transverse momentum resolution, which requires the path length of the reconstructed tracks
acts-project · Aug 11, 2021 · e98107c · e98107c
1 parent af0ab90
commit e98107c
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diff --git a/Examples/Io/Root/include/ActsExamples/Io/Root/RootTrajectoryStatesWriter.hpp b/Examples/Io/Root/include/ActsExamples/Io/Root/RootTrajectoryStatesWriter.hpp
@@ -106,6 +106,7 @@ class RootTrajectoryStatesWriter final : public WriterT<TrajectoriesContainer> {
   std::vector<int> m_volumeID;      ///< volume identifier
   std::vector<int> m_layerID;       ///< layer identifier
   std::vector<int> m_moduleID;      ///< surface identifier
+  std::vector<float> m_pathLength;  ///< path length
   std::vector<float> m_lx_hit;      ///< uncalibrated measurement local x
   std::vector<float> m_ly_hit;      ///< uncalibrated measurement local y
   std::vector<float> m_x_hit;       ///< uncalibrated measurement global x

diff --git a/Examples/Io/Root/src/RootTrajectoryStatesWriter.cpp b/Examples/Io/Root/src/RootTrajectoryStatesWriter.cpp
@@ -95,6 +95,7 @@ ActsExamples::RootTrajectoryStatesWriter::RootTrajectoryStatesWriter(
     m_outputTree->Branch("volume_id", &m_volumeID);
     m_outputTree->Branch("layer_id", &m_layerID);
     m_outputTree->Branch("module_id", &m_moduleID);
+    m_outputTree->Branch("pathLength", &m_pathLength);
     m_outputTree->Branch("l_x_hit", &m_lx_hit);
     m_outputTree->Branch("l_y_hit", &m_ly_hit);
     m_outputTree->Branch("g_x_hit", &m_x_hit);
@@ -365,6 +366,9 @@ ActsExamples::ProcessCode ActsExamples::RootTrajectoryStatesWriter::writeT(
         m_layerID.push_back(geoID.layer());
         m_moduleID.push_back(geoID.sensitive());
 
+        // get the path length
+        m_pathLength.push_back(state.pathLength());
+
         // expand the local measurements into the full bound space
         Acts::BoundVector meas =
             state.projector().transpose() * state.calibrated();
@@ -581,6 +585,7 @@ ActsExamples::ProcessCode ActsExamples::RootTrajectoryStatesWriter::writeT(
       m_volumeID.clear();
       m_layerID.clear();
       m_moduleID.clear();
+      m_pathLength.clear();
       m_lx_hit.clear();
       m_ly_hit.clear();
       m_x_hit.clear();