Merge pull request #47484 from 24LopezR/DDM_124X_FixDisplacedSUSYSim

[124X] Fix for long-lived slepton simulation

Author: cmsbuild

Diff for: Configuration/ProcessModifiers/python/fixLongLivedSleptonSim_cff.py

@@ -0,0 +1,4 @@
+import FWCore.ParameterSet.Config as cms
+
+# Designed to disable a bug affecting long lived slepton decays in HepMC-G4 interface
+fixLongLivedSleptonSim = cms.Modifier()

Diff for: SimG4Core/Application/python/g4SimHits_cfi.py

@@ -257,6 +257,7 @@
         ApplyLumiMonitorCuts = cms.bool(False), ## primary for lumi monitors
         Verbosity = cms.untracked.int32(0),
         FixG4Primary = cms.bool(False),
+        IsSlepton = cms.bool(False),
         PDGselection = cms.PSet(
             PDGfilterSel = cms.bool(False),        ## filter out unwanted particles
             PDGfilter = cms.vint32(21,1,2,3,4,5,6) ## list of unwanted particles (gluons and quarks)
@@ -694,3 +695,11 @@
 hgcaltb.toModify(g4SimHits,
                  OnlySDs = ['AHcalSensitiveDetector', 'HGCSensitiveDetector', 'HGCalTB1601SensitiveDetector', 'HcalTB06BeamDetector']
 )
+
+##
+## Fix for long-lived slepton simulation
+##
+from Configuration.ProcessModifiers.fixLongLivedSleptonSim_cff import fixLongLivedSleptonSim
+fixLongLivedSleptonSim.toModify( g4SimHits,
+                                 Generator = dict(IsSlepton = True)
+)

Diff for: SimG4Core/Generators/interface/Generator.h

@@ -46,6 +46,7 @@ class Generator {
   bool fPhiCuts;
   bool fFixG4Primary;
   bool fFiductialCuts;
+  bool fSlepton;
   double theMinPhiCut;
   double theMaxPhiCut;
   double theMinEtaCut;

Diff for: SimG4Core/Generators/src/Generator.cc

@@ -26,6 +26,7 @@ Generator::Generator(const ParameterSet &p)
       fEtaCuts(p.getParameter<bool>("ApplyEtaCuts")),
       fPhiCuts(p.getParameter<bool>("ApplyPhiCuts")),
       fFixG4Primary(p.getParameter<bool>("FixG4Primary")),
+      fSlepton(p.getParameter<bool>("IsSlepton")),
       theMinPhiCut(p.getParameter<double>("MinPhiCut")),  // in radians (CMS standard)
       theMaxPhiCut(p.getParameter<double>("MaxPhiCut")),
       theMinEtaCut(p.getParameter<double>("MinEtaCut")),
@@ -366,7 +367,7 @@ void Generator::HepMC2G4(const HepMC::GenEvent *evt_orig, G4Event *g4evt) {
           // Decay chain outside the fiducial cylinder defined by theRDecLenCut
           // are used for Geant4 tracking with predefined decay channel
           // In the case of decay in vacuum particle is not tracked by Geant4
-        } else if (2 == status && x2 * x2 + y2 * y2 >= theDecRCut2 && std::abs(z2) < Z_hector) {
+        } else if (2 == status && x2 * x2 + y2 * y2 >= theDecRCut2 && (fSlepton || std::abs(z2) < Z_hector)) {
           toBeAdded = true;
           if (verbose > 1)
             edm::LogVerbatim("SimG4CoreGenerator") << "GenParticle barcode = " << (*pitr)->barcode() << " passed case 2"
@@ -476,9 +477,14 @@ void Generator::particleAssignDaughters(G4PrimaryParticle *g4p, HepMC::GenPartic
       LogDebug("SimG4CoreGenerator::particleAssignDaughters")
           << "Assigning a " << (*vpdec)->pdg_id() << " as daughter of a " << vp->pdg_id() << " status=" << status;
 
-    bool checkStatus = fFixG4Primary
-                           ? ((status == 23 && std::abs(vp->pdg_id()) == 1000015) || (status > 50 && status < 100))
-                           : status > 3;
+    bool isInList;
+    if (fSlepton) {
+      std::vector<int> fParticleList = {1000011, 1000013, 1000015, 2000011, 2000013, 2000015};
+      isInList = (std::find(fParticleList.begin(), fParticleList.end(), std::abs(vp->pdg_id())) != fParticleList.end());
+    } else {
+      isInList = std::abs(vp->pdg_id()) == 1000015;
+    }
+    bool checkStatus = fFixG4Primary ? ((status == 23 && isInList) || (status > 50 && status < 100)) : status > 3;
 
     if ((status == 2 || checkStatus) && (*vpdec)->end_vertex() != nullptr) {
       double x2 = (*vpdec)->end_vertex()->position().x();