VertexBeamspotOrigins.cc

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#include "VertexBeamspotOrigins.h"

VertexBeamspotOrigins::VertexBeamspotOrigins(const edm::ParameterSet& regPSet, edm::ConsumesCollector& iC) {
  // operation mode
  std::string operationModeString       = regPSet.getParameter<std::string>("operationMode");
  if      (operationModeString == "BeamSpotFixed") m_operationMode = OperationMode::BEAM_SPOT_FIXED;
  else if (operationModeString == "BeamSpotSigma") m_operationMode = OperationMode::BEAM_SPOT_SIGMA;
  else if (operationModeString == "VerticesFixed") m_operationMode = OperationMode::VERTICES_FIXED;
  else if (operationModeString == "VerticesSigma") m_operationMode = OperationMode::VERTICES_SIGMA;
  else  throw cms::Exception("Configuration") <<"Unknown operation mode string: "<<operationModeString;

  token_beamSpot     = iC.consumes<reco::BeamSpot>(regPSet.getParameter<edm::InputTag>("beamSpot"));
  m_maxNVertices     = 1;
  if (m_operationMode == OperationMode::VERTICES_FIXED || m_operationMode == OperationMode::VERTICES_SIGMA) {
    token_vertex       = iC.consumes<reco::VertexCollection>(regPSet.getParameter<edm::InputTag>("vertexCollection"));
    m_maxNVertices     = regPSet.getParameter<int>("maxNVertices");
  }

  // mode-dependent z-halflength of tracking regions
  m_zErrorBeamSpot   = regPSet.getParameter<double>("zErrorBeamSpot");
  if (m_operationMode == OperationMode::VERTICES_SIGMA)  m_nSigmaZVertex   = regPSet.getParameter<double>("nSigmaZVertex");
  if (m_operationMode == OperationMode::VERTICES_FIXED)  m_zErrorVertex     = regPSet.getParameter<double>("zErrorVertex");
  m_nSigmaZBeamSpot = -1.;
  if (m_operationMode == OperationMode::BEAM_SPOT_SIGMA) {
    m_nSigmaZBeamSpot = regPSet.getParameter<double>("nSigmaZBeamSpot");
    if (m_nSigmaZBeamSpot < 0.)
      throw cms::Exception("Configuration") << "nSigmaZBeamSpot must be positive for BeamSpotSigma mode!";
  }
}

void VertexBeamspotOrigins::fillDescriptions(edm::ParameterSetDescription& desc, const std::string& defaultBeamSpot,
                                             const std::string& defaultVertex, int defaultMaxVertices) {
  desc.add<std::string>("operationMode", "BeamSpotFixed");
  desc.add<edm::InputTag>("beamSpot", defaultBeamSpot);
  desc.add<edm::InputTag>("vertexCollection", defaultVertex);
  desc.add<int>("maxNVertices", defaultMaxVertices);

  desc.add<double>("nSigmaZBeamSpot", 4.);
  desc.add<double>("zErrorBeamSpot", 24.2);
  desc.add<double>("nSigmaZVertex", 3.);
  desc.add<double>("zErrorVertex", 0.2);
}

VertexBeamspotOrigins::Origins VertexBeamspotOrigins::origins(const edm::Event& iEvent) const {
  Origins ret;

  // always need the beam spot (as a fall back strategy for vertex modes)
  edm::Handle< reco::BeamSpot > bs;
  iEvent.getByToken( token_beamSpot, bs );
  if( !bs.isValid() ) return ret;

  // this is a default origin for all modes
  GlobalPoint default_origin( bs->x0(), bs->y0(), bs->z0() );

  // fill the origins and halfLengths depending on the mode
  if (m_operationMode == OperationMode::BEAM_SPOT_FIXED || m_operationMode == OperationMode::BEAM_SPOT_SIGMA) {
    ret.emplace_back(default_origin,
                     (m_operationMode == OperationMode::BEAM_SPOT_FIXED) ? m_zErrorBeamSpot : m_nSigmaZBeamSpot*bs->sigmaZ() );
  } else if (m_operationMode == OperationMode::VERTICES_FIXED || m_operationMode == OperationMode::VERTICES_SIGMA) {
    edm::Handle< reco::VertexCollection > vertices;
    iEvent.getByToken( token_vertex, vertices );
    int n_vert = 0;
    for(const auto& v: *vertices) {
      if(v.isFake() || !v.isValid()) continue;

      ret.emplace_back( GlobalPoint( v.x(), v.y(), v.z() ),
                        (m_operationMode == OperationMode::VERTICES_FIXED) ? m_zErrorVertex : m_nSigmaZVertex*v.zError() );
      ++n_vert;
      if(m_maxNVertices >= 0 && n_vert >= m_maxNVertices) {
        break;
      }
    }
    // no-vertex fall-back case:
    if(ret.empty()) {
      ret.emplace_back( default_origin,
                        (m_nSigmaZBeamSpot > 0.) ? m_nSigmaZBeamSpot*bs->z0Error() : m_zErrorBeamSpot );
    }
  }

  return ret;
}