Phase2StripCPE.cc

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#include "RecoLocalTracker/Phase2TrackerRecHits/interface/Phase2StripCPE.h"
#include "Geometry/CommonTopologies/interface/PixelTopology.h"
#include "FWCore/MessageLogger/interface/MessageLogger.h"

Phase2StripCPE::Phase2StripCPE(edm::ParameterSet& conf,
                               const MagneticField& magf,
                               const TrackerGeometry& geom,
                               const SiPhase2OuterTrackerLorentzAngle& LorentzAngle)
    : magfield_(magf),
      geom_(geom),
      lorentzAngleMap_(LorentzAngle),
      tanLorentzAnglePerTesla_(conf.getParameter<double>("TanLorentzAnglePerTesla")) {
  use_LorentzAngle_DB_ = conf.getParameter<bool>("LorentzAngle_DB");
  fillParam();
}

Phase2StripCPE::LocalValues Phase2StripCPE::localParameters(const Phase2TrackerCluster1D& cluster,
                                                            const GeomDetUnit& detunit) const {
  auto const& p = m_Params[detunit.index() - m_off];
  auto const& topo = *p.topology;
  float ix = cluster.center() - 0.5f * p.coveredStrips;
  float iy = float(cluster.column()) + 0.5f;  // halfway the column

  LocalPoint lp(topo.localX(ix), topo.localY(iy), 0);  // x, y, z

  return std::make_pair(lp, p.localErr);
}

LocalVector Phase2StripCPE::driftDirection(const Phase2TrackerGeomDetUnit& det) const {
  LocalVector lbfield = (det.surface()).toLocal(magfield_.inTesla(det.surface().position()));

  float langle =
      use_LorentzAngle_DB_ ? lorentzAngleMap_.getLorentzAngle(det.geographicalId().rawId()) : tanLorentzAnglePerTesla_;

  float dir_x = -langle * lbfield.y();
  float dir_y = langle * lbfield.x();
  float dir_z = 1.f;  // E field always in z direction

  return LocalVector(dir_x, dir_y, dir_z);
}

void Phase2StripCPE::fillParam() {
  // in phase 2 they are all pixel topologies...
  auto const& dus = geom_.detUnits();
  m_off = dus.size();
  // skip Barrel and Foward pixels...
  for (unsigned int i = 3; i < 7; ++i) {
    LogDebug("LookingForFirstPhase2OT") << " Subdetector " << i << " GeomDetEnumerator "
                                        << GeomDetEnumerators::tkDetEnum[i] << " offset "
                                        << geom_.offsetDU(GeomDetEnumerators::tkDetEnum[i]) << std::endl;
    if (geom_.offsetDU(GeomDetEnumerators::tkDetEnum[i]) != dus.size()) {
      if (geom_.offsetDU(GeomDetEnumerators::tkDetEnum[i]) < m_off)
        m_off = geom_.offsetDU(GeomDetEnumerators::tkDetEnum[i]);
    }
  }
  LogDebug("LookingForFirstPhase2OT") << " Chosen offset: " << m_off;

  m_Params.resize(dus.size() - m_off);
  // very very minimal, for sure it will need to expand...
  for (auto i = m_off; i != dus.size(); ++i) {
    auto& p = m_Params[i - m_off];

    const Phase2TrackerGeomDetUnit& det = (const Phase2TrackerGeomDetUnit&)(*dus[i]);
    assert(det.index() == int(i));
    p.topology = &det.specificTopology();

    auto pitch_x = p.topology->pitch().first;
    auto pitch_y = p.topology->pitch().second;

    // see https://github.com/cms-sw/cmssw/blob/CMSSW_8_1_X/RecoLocalTracker/SiStripRecHitConverter/src/StripCPE.cc
    auto thickness = det.specificSurface().bounds().thickness();
    auto drift = driftDirection(det) * thickness;
    auto lvec = drift + LocalVector(0, 0, -thickness);
    p.coveredStrips = lvec.x() / pitch_x;  // simplifies wrt Phase0 tracker because only rectangular modules

    constexpr float o12 = 1. / 12;
    p.localErr = LocalError(o12 * pitch_x * pitch_x, 0, o12 * pitch_y * pitch_y);  // e2_xx, e2_xy, e2_yy
  }
}