[PWGHF] Add possibility to reapply trigger selections in Xic+ candidate creator (#16732)

Author: fgrosa

PWGHF/TableProducer/candidateCreatorXicToXiPiPi.cxx

@@ -111,12 +111,21 @@ struct HfCandidateCreatorXicToXiPiPi {
   Configurable<bool> constrainXicPlusToPv{"constrainXicPlusToPv", false, "Constrain XicPlus to PV"};
   Configurable<int> kfConstructMethod{"kfConstructMethod", 2, "Construct method of XicPlus: 0 fast mathematics without constraint of fixed daughter particle masses, 2 daughter particle masses stay fixed in construction process"};
   Configurable<bool> rejDiffCollTrack{"rejDiffCollTrack", true, "Reject tracks coming from different collisions (effective only for KFParticle w/o derived data)"};
+  // configurables for software trigger selections
+  struct : ConfigurableGroup {
+    std::string prefix = "softtrig";
+    Configurable<bool> applySoftwareTrigSelections{"applySoftwareTrigSelections", false, "Enable application of software trigger selections"};
+    Configurable<float> minDecayLength{"minDecayLength", 0.015, "Minimum decay length (computed with DCAFitter)"};
+    Configurable<float> minCosPA{"minCosPA", 0.9, "Minimum coine of pointing angle (computed with DCAFitter)"};
+    Configurable<float> maxChi2Pca{"maxChi2Pca", 3., "Maximum chi2 PCA (computed with DCAFitter)"};
+  } softTrigCuts;
 
   Service<o2::ccdb::BasicCCDBManager> ccdb{};
   o2::base::MatLayerCylSet* lut{};
   o2::base::Propagator::MatCorrType matCorr = o2::base::Propagator::MatCorrType::USEMatCorrLUT;
 
   o2::vertexing::DCAFitterN<3> df;
+  o2::vertexing::DCAFitterN<2> df2Prong;
 
   HfEventSelection hfEvSel;
 
@@ -196,6 +205,66 @@ struct HfCandidateCreatorXicToXiPiPi {
     df.setMinRelChi2Change(minRelChi2Change);
     df.setUseAbsDCA(useAbsDCA);
     df.setWeightedFinalPCA(useWeightedFinalPCA);
+
+    if (softTrigCuts.applySoftwareTrigSelections) {
+      float maxRadSoftTrig = 200.;
+      float maxDZIniSoftTrig = 1.e9;
+      float maxDXYIniSoftTrig = 4.;
+      float minParamChangeSoftTrig = 1.e-3;
+      float maxChi2SoftTrig = 0.9;
+      float minRelChi2ChangeSoftTrig = 0.9;
+      df2Prong.setPropagateToPCA(true);
+      df2Prong.setMaxR(maxRadSoftTrig);
+      df2Prong.setMaxDZIni(maxDZIniSoftTrig);
+      df2Prong.setMaxDXYIni(maxDXYIniSoftTrig);
+      df2Prong.setMinParamChange(minParamChangeSoftTrig);
+      df2Prong.setMinRelChi2Change(minRelChi2ChangeSoftTrig);
+      df2Prong.setMaxChi2(maxChi2SoftTrig);
+      df2Prong.setUseAbsDCA(false);
+      df2Prong.setWeightedFinalPCA(false);
+    }
+  }
+
+  /// Method that reapplies the selections applied in the software trigger
+  /// \param pVecCascade is the cascade momentum vector
+  /// \param trackParBachelor is the array with two bachelor track parametrisations
+  /// \param collision is the collision containing the candidate
+  template <typename TTrackParCov, typename Coll>
+  bool isSelectedXicSoftwareTriggers(std::array<float, 3> const& pVecCascade, std::array<TTrackParCov, 2> const& trackParBachelor, Coll const& collision)
+  {
+    int nCand{0};
+    try {
+      nCand = df2Prong.process(trackParBachelor[0], trackParBachelor[1]);
+    } catch (...) {
+      LOG(error) << "Exception caught in DCA fitter process call for bachelor + bachelor in software trigger selection function!";
+      return false;
+    }
+    if (nCand == 0) {
+      return false;
+    }
+
+    const auto& vtx = df2Prong.getPCACandidate();
+    if (df2Prong.getChi2AtPCACandidate() > softTrigCuts.maxChi2Pca) {
+      return false;
+    }
+
+    std::array<float, 3> pVecBachFirst{}, pVecBachSecond{};
+    const auto& trackBachFirstProp = df2Prong.getTrack(0);
+    const auto& trackBachSecondProp = df2Prong.getTrack(1);
+    trackBachFirstProp.getPxPyPzGlo(pVecBachFirst);
+    trackBachSecondProp.getPxPyPzGlo(pVecBachSecond);
+    auto momXiBachBach = RecoDecay::pVec(pVecCascade, pVecBachFirst, pVecBachSecond);
+
+    std::array<float, 3> primVtx = {collision.posX(), collision.posY(), collision.posZ()};
+    if (RecoDecay::cpa(primVtx, std::array{vtx[0], vtx[1], vtx[2]}, momXiBachBach) < softTrigCuts.minCosPA) {
+      return false;
+    }
+
+    if (RecoDecay::distance(primVtx, vtx) < softTrigCuts.minDecayLength) {
+      return false;
+    }
+
+    return true;
   }
 
   template <o2::hf_centrality::CentralityEstimator CentEstimator, typename Collision>
@@ -282,6 +351,13 @@ struct HfCandidateCreatorXicToXiPiPi {
       auto trackParCovCharmBachelor0 = getTrackParCov(trackCharmBachelor0);
       auto trackParCovCharmBachelor1 = getTrackParCov(trackCharmBachelor1);
 
+      // if enabled, apply selections of software trigger
+      if (softTrigCuts.applySoftwareTrigSelections) {
+        if (!isSelectedXicSoftwareTriggers(pVecCasc, std::array{trackParCovCharmBachelor0, trackParCovCharmBachelor1}, collision)) {
+          continue;
+        }
+      }
+
       // reconstruct the 3-prong secondary vertex
       try {
         if (df.process(trackCasc, trackParCovCharmBachelor0, trackParCovCharmBachelor1) == 0) {
@@ -459,9 +535,20 @@ struct HfCandidateCreatorXicToXiPiPi {
         continue;
       }
       auto casc = cascAodElement.kfCascData_as<KFCascFull>();
+
       auto trackCharmBachelor0 = rowTrackIndexXicPlus.prong0_as<TracksWCovExtraPidPrPi>();
       auto trackCharmBachelor1 = rowTrackIndexXicPlus.prong1_as<TracksWCovExtraPidPrPi>();
 
+      // if enabled, apply selections of software trigger
+      if (softTrigCuts.applySoftwareTrigSelections) {
+        auto trackParCovCharmBachelor0 = getTrackParCov(trackCharmBachelor0);
+        auto trackParCovCharmBachelor1 = getTrackParCov(trackCharmBachelor1);
+        std::array<float, 3> const pVecCasc = {casc.px(), casc.py(), casc.pz()};
+        if (!isSelectedXicSoftwareTriggers(pVecCasc, std::array{trackParCovCharmBachelor0, trackParCovCharmBachelor1}, collision)) {
+          continue;
+        }
+      }
+
       //-------------------preselect cascade candidates--------------------------------------
       if (doCascadePreselection) {
         if (std::abs(casc.dcaXYCascToPV()) > dcaXYToPVCascadeMax) {