ITS: add preliminary cell cuts

Author: f3sch

Detectors/ITSMFT/ITS/tracking/CMakeLists.txt

@@ -32,7 +32,7 @@ o2_add_library(ITStracking
                PRIVATE_LINK_LIBRARIES
                        O2::Steer
                        TBB::tbb)
-target_compile_options(${targetName} PRIVATE -O0 -g -fPIC -fno-omit-frame-pointer)
+# target_compile_options(${targetName} PRIVATE -O0 -g -fPIC -fno-omit-frame-pointer)
 
 o2_add_library(ITSTrackingInterface
                TARGETVARNAME targetName
@@ -41,7 +41,7 @@ o2_add_library(ITSTrackingInterface
                        O2::ITStracking
                        O2::Framework
                        O2::GPUTracking)
-target_compile_options(${targetName} PRIVATE -O0 -g -fPIC -fno-omit-frame-pointer)
+# target_compile_options(${targetName} PRIVATE -O0 -g -fPIC -fno-omit-frame-pointer)
 
 o2_target_root_dictionary(ITStracking
                           HEADERS include/ITStracking/Tracklet.h

Detectors/ITSMFT/ITS/tracking/include/ITStracking/Configuration.h

@@ -57,6 +57,7 @@ struct TrackingParameters {
   int NTimeSlices{1};
   /// Trackleting cuts
   float TrackletMinPt = 0.3f;
+  float TrackletNSigmaVtxZ{-1.f};
   /// Cell finding cuts
   float CellDeltaTanLambdaSigma = 0.007f;
   /// Fitter parameters
@@ -84,6 +85,8 @@ struct TrackingParameters {
   float SeedingMaxChi2Iter{3.f};           // maximum chi2 change required to end iteration
   float SeedingTukeyStartIter{5.f};        // start value for tukey scaling for iteration
   float SeedingMinWghTrk{0.05f};           // minimum weight a track has to have to be accounted
+  float SeedingMinPtTrk{0.0};              // minimum pt for cells to enter pool
+  float SeedingMaxTglTrk{6.f};             // maximum accepted tgl for cells to enter pool
   int SeedingMaxFitIter{3};                // maximum iterations for fit
   int SeedingMinTracksIter{50};            // minimum tracks needed for one iteration
   int SeedingDBScanMinPt{100};             // DBSCAN: minimum number of cluster points

Detectors/ITSMFT/ITS/tracking/include/ITStracking/MathUtils.h

@@ -78,7 +78,7 @@ GPUhdi() float computeCurvatureCentreX(float x1, float y1, float x2, float y2, f
 
 GPUhdi() float computeTanDipAngle(float x1, float y1, float x2, float y2, float z1, float z2)
 {
-  // in case the points vertically align we go to pos/neg inifinity.
+  // in case the points vertically align we go to pos/neg infinity.
   const float d = o2::gpu::CAMath::Hypot(x1 - x2, y1 - y2);
   if (o2::gpu::CAMath::Abs(d) < o2::its::constants::Tolerance) {
     return ((z1 > z2) ? -1.f : 1.f) * o2::constants::math::VeryBig;
@@ -96,6 +96,11 @@ GPUhdi() float Sq(float v)
   return v * v;
 }
 
+GPUhdi() float SqDiff(float x, float y)
+{
+  return Sq(x - y);
+}
+
 GPUhdi() float MSangle(float mass, float p, float xX0)
 {
   float beta = p / o2::gpu::CAMath::Hypot(mass, p);

Detectors/ITSMFT/ITS/tracking/src/Configuration.cxx

@@ -198,6 +198,7 @@ std::vector<RecoIteration> TrackingMode::getRecoIterations(TrackingMode::Type mo
     recoIterations[0].steps.set(kRunTrackleting, kRunCellFinding, kRunCellSeeding, kUpdateClusters);
     recoIterations[0].params.NLayers = 3;                                                   // only do cell finding up until the third layer
     recoIterations[0].params.UseDiamond = true;                                             // use the blown up diamond constrain to (e.g. luminous region)
+    recoIterations[0].params.TrackletNSigmaVtxZ = 1.f;                                      // since diamond is used restrict at least to fit within luminous
     recoIterations[0].params.CorrType = o2::base::PropagatorF::MatCorrType::USEMatCorrNONE; // do not use material
     recoIterations[0].params.SeedingDCATolerance = tc.seedingDCATolerance;
     recoIterations[0].params.SeedingDCAMaxPull = tc.seedingDCAMaxPull;

Detectors/ITSMFT/ITS/tracking/src/TrackerTraits.cxx

@@ -183,6 +183,18 @@ void TrackerTraits<NLayers>::computeLayerTracklets(const int iteration, const in
                     ((deltaPhi < mTimeFrame->getPhiCut(iLayer) || o2::gpu::GPUCommonMath::Abs(deltaPhi - o2::constants::math::TwoPI) < mTimeFrame->getPhiCut(iLayer)))) {
                   const float phi{o2::gpu::CAMath::ATan2(currentCluster.yCoordinate - nextCluster.yCoordinate, currentCluster.xCoordinate - nextCluster.xCoordinate)};
                   const float tanL = (currentCluster.zCoordinate - nextCluster.zCoordinate) / (currentCluster.radius - nextCluster.radius);
+
+                  if (mRecoParams[iteration].params.TrackletNSigmaVtxZ > 0) {
+                    // Check if assumed line extrapolation is compatible with current vertex
+                    // use straighline approximation to vertex radius
+                    // TODO account for cluster z errs
+                    const float zAtVtx = nextCluster.zCoordinate + (tanL * (pv.getR() - nextCluster.radius));
+                    const float zChi2 = math_utils::SqDiff(nextCluster.zCoordinate, pv.getZ()) / (pv.getSigmaZ2());
+                    if (zChi2 > mRecoParams[iteration].params.TrackletNSigmaVtxZ) {
+                      continue;
+                    }
+                  }
+
                   if constexpr (decltype(Tag)::value == PassMode::OnePass::value) {
                     tracklets.emplace_back(currentSortedIndex, mTimeFrame->getSortedIndex(targetROF, iLayer + 1, iNext), tanL, phi, pivotROF, targetROF);
                   } else if constexpr (decltype(Tag)::value == PassMode::TwoPassCount::value) {
@@ -511,6 +523,13 @@ void TrackerTraits<NLayers>::findCellSeeds(const int iteration)
     tbb::parallel_for(size_t(0), cells.size(), [&](size_t iCell) {
       // relate each cell to the imposed mean vertex or assumed beamline if the former is not provided
       auto& cell = cells[iCell];
+      // impose general quality cuts
+      if (o2::gpu::CAMath::Abs(cell.getTgl()) > mRecoParams[iteration].params.SeedingMaxTglTrk) {
+        return;
+      }
+      if (cell.getPt() < mRecoParams[iteration].params.SeedingMinPtTrk) {
+        return;
+      }
       dataformats::VertexBase vtx;
       dataformats::DCA dca;
       float z = cell.getZAt(0., getBz());