StubPtConsistency.cc

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#include <iostream>
#include <memory>

#include "L1Trigger/TrackTrigger/interface/StubPtConsistency.h"
#include "CLHEP/Units/PhysicalConstants.h"

namespace StubPtConsistency {

  float getConsistency(TTTrack<Ref_Phase2TrackerDigi_> aTrack,
                       const TrackerGeometry* theTrackerGeom,
                       const TrackerTopology* tTopo,
                       double mMagneticFieldStrength,
                       int nPar) {
    if (!(nPar == 4 || nPar == 5))
      throw cms::Exception("IncorrectInput") << "Not a valid nPar option!";

    double trk_bendchi2 = 0.0;
    double bend_resolution = 0.483;
    // B*c/2E11 - converts q/pt to track angle at some radius from beamline
    float speedOfLightConverted = CLHEP::c_light / 1.0E5;

    // Need the pT signed in order to determine if bend is positive or negative
    // P(MeV/c) = (c/10^9)·Q·B(kG)·R(cm)
    float trk_signedPt = speedOfLightConverted * mMagneticFieldStrength / aTrack.rInv();

    // loop over stubs
    const auto& stubRefs = aTrack.getStubRefs();
    int nStubs = stubRefs.size();

    for (const auto& stubRef : stubRefs) {
      DetId detIdStub = theTrackerGeom->idToDet((stubRef->clusterRef(0))->getDetId())->geographicalId();
      MeasurementPoint coords = stubRef->clusterRef(0)->findAverageLocalCoordinatesCentered();
      const GeomDet* theGeomDet = theTrackerGeom->idToDet(detIdStub);
      Global3DPoint posStub = theGeomDet->surface().toGlobal(theGeomDet->topology().localPosition(coords));

      float stub_r = posStub.perp();
      float stub_z = posStub.z();

      bool isBarrel = (detIdStub.subdetId() == StripSubdetector::TOB);

      const GeomDetUnit* det0 = theTrackerGeom->idToDetUnit(detIdStub);
      const GeomDetUnit* det1 = theTrackerGeom->idToDetUnit(tTopo->partnerDetId(detIdStub));
      const PixelGeomDetUnit* unit = reinterpret_cast<const PixelGeomDetUnit*>(det0);
      const PixelTopology& topo = unit->specificTopology();

      // Calculation of snesor spacing obtained from TMTT: https://github.com/CMS-TMTT/cmssw/blob/TMTT_938/L1Trigger/TrackFindingTMTT/src/Stub.cc#L138-L146
      float stripPitch = topo.pitch().first;

      float modMinR = std::min(det0->position().perp(), det1->position().perp());
      float modMaxR = std::max(det0->position().perp(), det1->position().perp());
      float modMinZ = std::min(det0->position().z(), det1->position().z());
      float modMaxZ = std::max(det0->position().z(), det1->position().z());
      float sensorSpacing = sqrt((modMaxR - modMinR) * (modMaxR - modMinR) + (modMaxZ - modMinZ) * (modMaxZ - modMinZ));

      // Approximation of phiOverBendCorrection, from TMTT: https://github.com/CMS-TMTT/cmssw/blob/TMTT_938/L1Trigger/TrackFindingTMTT/src/Stub.cc#L440-L448
      bool tiltedBarrel = (isBarrel && tTopo->tobSide(detIdStub) != 3);
      float gradient = 0.886454;
      float intercept = 0.504148;
      float correction;
      if (tiltedBarrel)
        correction = gradient * fabs(stub_z) / stub_r + intercept;
      else if (isBarrel)
        correction = 1;
      else
        correction = fabs(stub_z) / stub_r;

      float stubBend = stubRef->bendFE();
      if (!isBarrel && stub_z < 0.0)
        stubBend = -stubBend;  // flip sign of bend if in negative end cap

      float trackBend = -(sensorSpacing * stub_r * mMagneticFieldStrength * (speedOfLightConverted / 2)) /
                        (stripPitch * trk_signedPt * correction);
      float bendDiff = trackBend - stubBend;

      trk_bendchi2 += (bendDiff * bendDiff) / (bend_resolution * bend_resolution);
    }  // end loop over stubs

    float bendchi2 = trk_bendchi2 / nStubs;
    return bendchi2;
  }  //end getConsistency()
}  // namespace StubPtConsistency