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Fix for FastSim decays of exotic-descendent SM particles decaying outside pipe #36122

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merged 4 commits into from Dec 1, 2021
Merged

Fix for FastSim decays of exotic-descendent SM particles decaying outside pipe #36122

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1066de4
added lines to skip FastSim decays for SM particles that cross the be…
sbein Nov 14, 2021
3cdd06b
post code checks
sbein Nov 15, 2021
d3a116f
taking @perrotta's suggestion and reducing repetition of calculations
sbein Nov 30, 2021
2fe14d6
ran formatting again
sbein Nov 30, 2021
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3 changes: 2 additions & 1 deletion FastSimulation/SimplifiedGeometryPropagator/interface/ParticleManager.h
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Expand Up @@ -146,7 +146,8 @@ inline bool isExotic(int pdgid_) {
return ((pdgid >= 1000000 && pdgid < 4000000 && pdgid != 3000022) || // SUSY, R-hadron, and technicolor particles
pdgid == 17 || // 4th generation lepton
pdgid == 34 || // W-prime
pdgid == 37); // charged Higgs
pdgid == 37 || // charged Higgs
pdgid == 39); // bulk graviton
}

#endif
16 changes: 12 additions & 4 deletions FastSimulation/SimplifiedGeometryPropagator/src/ParticleManager.cc
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Expand Up @@ -216,19 +216,27 @@ std::unique_ptr<fastsim::Particle> fastsim::ParticleManager::nextGenParticle() {
}
// particles which do not descend from exotics must be produced within the beampipe
int exoticRelativeId = 0;
if (productionVertex->position().perp2() * lengthUnitConversionFactor2_ > beamPipeRadius2_) //
{
const bool producedWithinBeamPipe =
productionVertex->position().perp2() * lengthUnitConversionFactor2_ < beamPipeRadius2_;
if (producedWithinBeamPipe) {
exoticRelativesChecker(productionVertex, exoticRelativeId, 0);
if (!isExotic(exoticRelativeId)) {
continue;
}
}

// particle must not decay before it reaches the beam pipe
if (endVertex && endVertex->position().perp2() * lengthUnitConversionFactor2_ < beamPipeRadius2_) {
// FastSim will not make hits out of particles that decay before reaching the beam pipe
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@perrotta perrotta Nov 28, 2021 •
edited

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Especially because this is FastSim, it is probably worth trying to avoid repeated computations of the same quantities.
A possibile suggestion:

    // particles which do not descend from exotics must be produced within the beampipe
    int exoticRelativeId = 0;
    const bool producedWithinBeamPipe = 
        productionVertex->position().perp2() * lengthUnitConversionFactor2_ < beamPipeRadius2_;
    if (!producedWithinBeamPipe) {
      exoticRelativesChecker(productionVertex, exoticRelativeId, 0);
      if (!isExotic(exoticRelativeId)) {
        continue;
      }
    }

    // FastSim will not make hits out of particles that decay before reaching the beam pipe
    const bool decayedWithinBeamPipe =
        endVertex && endVertex->position().perp2() * lengthUnitConversionFactor2_ < beamPipeRadius2_;
    if (decayedWithinBeamPipe) {
      continue;
    }

    // SM particles that descend from exotics and cross the beam pipe radius should make hits but not be decayed
    if (producedWithinBeamPipe && !decayedWithinBeamPipe) {
      exoticRelativesChecker(productionVertex, exoticRelativeId, 0);
    }

const bool decayedWithinBeamPipe =
endVertex && endVertex->position().perp2() * lengthUnitConversionFactor2_ < beamPipeRadius2_;
if (decayedWithinBeamPipe) {
continue;
}

// SM particles that descend from exotics and cross the beam pipe radius should make hits but not be decayed
if (producedWithinBeamPipe && !decayedWithinBeamPipe) {
exoticRelativesChecker(productionVertex, exoticRelativeId, 0);
}

// make the particle
std::unique_ptr<Particle> newParticle(
new Particle(particle.pdg_id(),
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