VKalExtPropagator.cxx

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/*
  Copyright (C) 2002-2026 CERN for the benefit of the ATLAS collaboration
*/
//
// The VKalExtPropagator object is created if ATHENA propagator exists
// and is supplied via jobOptions. A pointer to it is supplied to VKalVrtCore
// for every vertex fit via VKalVrtControlBase object.
// VKalVrtCore uses it to extrapolate tracks for a vertex fit.
//
// If ATHENA propagator doesn't exist, the VKalVrtCore uses its internal
// propagator without material.
//
//-------------------------------------------------------------------------
 
 
// Header include
#include "TrkVKalVrtFitter/VKalExtPropagator.h"
 
#include "TrkVKalVrtFitter/TrkVKalVrtFitter.h"
#include "TrkSurfaces/CylinderSurface.h"
#include "TrkSurfaces/StraightLineSurface.h"
#include "AthContainers/ConstAccessor.h"
//-------------------------------------------------
#include <iostream>
 
 
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
//                  External propagator access for VKalVrt
 
namespace Trk {
 
  // Constructor
  VKalExtPropagator::VKalExtPropagator( TrkVKalVrtFitter* pnt)
  {
       m_extrapolator = nullptr;
       m_vkalFitSvc = pnt;
  }
  VKalExtPropagator::~VKalExtPropagator()= default;
 
 
  void VKalExtPropagator::setPropagator(const IExtrapolator*  Pnt)
  {
     m_extrapolator = Pnt;
  }
 
//Protection against exit outside ID volume (unless explicitly requested in configuration for LLP scenarios -- then uses MS volume)
//
  double VKalExtPropagator::Protection(const double *RefEnd,
                                       const IVKalState& istate) const
  {
      const TrkVKalVrtFitter::State& state = static_cast<const TrkVKalVrtFitter::State&> (istate);
 
      double Xend=RefEnd[0] + state.m_refFrameX;
      double Yend=RefEnd[1] + state.m_refFrameY;
      double Zend=RefEnd[2] + state.m_refFrameZ;
      
      double sizeR = state.m_allowUltraDisplaced ? m_vkalFitSvc->m_MSsizeR : m_vkalFitSvc->m_IDsizeR;
      double sizeZ = state.m_allowUltraDisplaced ? m_vkalFitSvc->m_MSsizeZ : m_vkalFitSvc->m_IDsizeZ;
      double Rlim=std::hypot(Xend, Yend) / sizeR;
      double Zlim=std::abs(Zend) / sizeZ;
 
      double Scale = Rlim; if(Zlim>Rlim) Scale=Zlim;
//std::cout<<"relative TARG="<<RefEnd[0]<<","<<RefEnd[1]<<","<<RefEnd[2]
//<<" global ref.="<<m_vkalFitSvc->state.m_refFrameX<<","<<m_vkalFitSvc->state.m_refFrameY<<","<<m_vkalFitSvc->state.m_refFrameZ
//<<" Limits="<<m_vkalFitSvc->m_IDsizeR<<","<<m_vkalFitSvc->m_IDsizeZ<<" scale="<<Scale<<'\n';
      return Scale;
  }
 
  bool VKalExtPropagator::checkTarget( double *RefEnd,
                                       const IVKalState& istate) const
  {
      //double targV[3]={ RefEnd[0], RefEnd[1], RefEnd[2]};
      return Protection(RefEnd, istate) <= 1.;
  }
/*----------------------------------------------------------------------------------*/
//  Addres of this fuction is supplied to TrkVKalVrtCore for ATLAS InDet extrapolation
//  with material. Each time VKalVrt needs propagation - it calls it.
//
//   In case of usage with first measured point
//    it always use this point as starting point,
//     so ParOld,CovOld,RefStart are irrelevant
//
//  VKalVrtCore works in relative coordinates wrt (state.m_refFrameX,state.m_refFrameY,state.m_refFrameZ)
//  For ATLAS propagator the Core coordinates must be moved back to global ref.frame
/*------------------------------------------------------------------------------------*/
  void VKalExtPropagator::Propagate( long int trkID, long int Charge, const double *ParOld,
                                     const double *CovOld, const double *RefStart, const double *RefEnd,
                                     double *ParNew, double *CovNew,
                                     IVKalState& istate) const
  {
      TrkVKalVrtFitter::State& state = static_cast<TrkVKalVrtFitter::State&> (istate);
 
      int trkID_loc=trkID; if(trkID_loc<0)trkID_loc=0;
//std::cout<<__func__<<" Ext.Propagator TrkID="<<trkID<<"to (local!!!)="<<RefEnd[0]<<", "<<RefEnd[1]<<", "<<RefEnd[2]<<'\n';
//-----------
      double vX=RefEnd[0]; double vY=RefEnd[1]; double vZ=RefEnd[2]; //relative coords
      // Propagation target in GLOBAL frame
      Amg::Vector3D endPointG( vX + state.m_refFrameX, vY + state.m_refFrameY, vZ + state.m_refFrameZ);
//
// ---- Make MeasuredPerigee from input. Mag.field at start point is used here
//
      std::span<const double, 5> PerigeeIni( ParOld, 5 );
      std::array<double, 15> CovPerigeeIni{};
      if( CovOld != nullptr) {
//        for(int i=0; i<15;i++) CovPerigeeIni.push_back( CovOld[i] );
        std::copy(CovOld,CovOld+15,CovPerigeeIni.begin() );
      }else{
//        for(int i=0; i<15;i++) CovPerigeeIni.push_back(0.);
        CovPerigeeIni[0]=1.e6;CovPerigeeIni[2]=1.e6;CovPerigeeIni[5]=1.;CovPerigeeIni[9]=1.;CovPerigeeIni[14]=fabs(PerigeeIni[4]);
      }
      //--- This creates Perigee in GLOBAL frame from input in realtive coordinates
      const Perigee* inpPer =
          m_vkalFitSvc->CreatePerigee( RefStart[0], RefStart[1], RefStart[2], PerigeeIni, CovPerigeeIni, state).release();
      const TrackParameters * inpPar= inpPer;
//
// ----- Magnetic field is taken at target point (GLOBAL calculated from relative frame input)
//
      double fx,fy,fz;
      state.m_fitField.getMagFld(vX,vY,vZ,fx,fy,fz);
//
//-------------------- Extrapolation itself
//
      const Trk::TrackParameters* endPer = myExtrapWithMatUpdate( trkID, inpPar, &endPointG, state);
//-----------------------------------
      if( endPer == nullptr ) {   // No extrapolation done!!!
        ParNew[0]=0.; ParNew[1]=0.;ParNew[2]=0.;ParNew[3]=0.;ParNew[4]=0.;
        delete inpPer; return;
      }
      const Perigee*          mPer = dynamic_cast<const Perigee*>(endPer);
      const AtaStraightLine*  Line = dynamic_cast<const AtaStraightLine*>(endPer);
      AmgVector(5) VectPerig; VectPerig.setZero();
      const AmgSymMatrix(5) *CovMtx=nullptr;
      if( mPer ){
        VectPerig = mPer->parameters();
        CovMtx    = mPer->covariance();
      }
      if( Line ){
        VectPerig = Line->parameters();
        CovMtx    = Line->covariance();
      }
      if( (Line==nullptr && mPer==nullptr) || CovMtx==nullptr ){
        ParNew[0]=0.; ParNew[1]=0.;ParNew[2]=0.;ParNew[3]=0.;ParNew[4]=0.;
        delete endPer;
        delete inpPer; 
        return;
      }
 
      if((*CovMtx)(0,0)<=0. || (*CovMtx)(1,1)<=0.){                     //protection against bad error matrix
        ParNew[0]=0.; ParNew[1]=0.;ParNew[2]=0.;ParNew[3]=0.;ParNew[4]=0.;
        delete inpPer; 
        delete endPer;
        return;
      }
      double CovVertTrk[15];
      long int locCharge=Charge;
      CovVertTrk[ 0] =(*CovMtx)(0,0);
      CovVertTrk[ 1] =(*CovMtx)(1,0);
      CovVertTrk[ 2] =(*CovMtx)(1,1);
      CovVertTrk[ 3] =(*CovMtx)(2,0);
      CovVertTrk[ 4] =(*CovMtx)(2,1);
      CovVertTrk[ 5] =(*CovMtx)(2,2);
      CovVertTrk[ 6] =(*CovMtx)(3,0);
      CovVertTrk[ 7] =(*CovMtx)(3,1);
      CovVertTrk[ 8] =(*CovMtx)(3,2);
      CovVertTrk[ 9] =(*CovMtx)(3,3);
      CovVertTrk[10] =(*CovMtx)(4,0);
      CovVertTrk[11] =(*CovMtx)(4,1);
      CovVertTrk[12] =(*CovMtx)(4,2);
      CovVertTrk[13] =(*CovMtx)(4,3);
      CovVertTrk[14] =(*CovMtx)(4,4);
//std::cout<<" extrapPoint="<<endPer->position().x()<<", "<<endPer->position().y()<<", "<<endPer->position().y()<<'\n';
//std::cout<<" extrapCov="<<(*CovMtx)(0,0)<<", "<<(*CovMtx)(1,1)<<", "<<(*CovMtx)(2,2)<<
//                                          ", "<<(*CovMtx)(3,3)<<", "<<(*CovMtx)(4,4)<<'\n';
 
      double effectiveBMAG=state.m_fitField.getEffField(fx, fy, fz, VectPerig[2], VectPerig[3]);
      if(fabs(effectiveBMAG) < 0.01) effectiveBMAG=0.01;
      if(CovNew != nullptr) {
         m_vkalFitSvc->VKalTransform( effectiveBMAG, VectPerig(0), VectPerig(1),
            VectPerig(2), VectPerig(3), VectPerig(4), CovVertTrk,
                      locCharge,  &ParNew[0] , &CovNew[0]);
      }else{
         double CovVertTrkTmp[15];
         m_vkalFitSvc->VKalTransform( effectiveBMAG, VectPerig(0), VectPerig(1),
            VectPerig(2), VectPerig(3), VectPerig(4), CovVertTrk,
                      locCharge,  &ParNew[0] , CovVertTrkTmp);
      }
      delete inpPer; delete endPer;
  }
 
 
/*--------------------------------------------------------------------------------------*/
/* Logic of material subtruction or addition to track error matrix is implemented here. */
/* What to do depends on direction of extrapolation and relative position of initial,   */
/* final and track reference points                                                     */
/*                                          */
/*    All points are in GLOBAL Atlas frame here!                    */
/*                                              */
/*   Real track (TrkID>=0) extrapolation always starts from INITIAL track object    */
/*   and NOT from parameters provided by VKalVrtCore. More CPU time but better precision*/
/*   Only combined (TrkID<0) tracks use VKalVrtCore parameters for start        */
/*--------------------------------------------------------------------------------------*/
  const TrackParameters* VKalExtPropagator::myExtrapWithMatUpdate(long int TrkID,
                                                                  const TrackParameters *inpPer,
                                                                  Amg::Vector3D * endPoint,
                                                                  const IVKalState& istate) const
  {
      const TrkVKalVrtFitter::State& state = static_cast<const TrkVKalVrtFitter::State&> (istate);
      const EventContext& ctx = (state.m_eventContext)
                                  ? *(state.m_eventContext)
                                  : Gaudi::Hive::currentContext();
 
      const Trk::TrackParameters* endPer=nullptr;
      const Trk::TrackParameters* tmpPer=nullptr;
      ParticleHypothesis prtType = pion;
      //End surface
      PerigeeSurface surfEnd( *endPoint );
      //Initial point (global frame)
      Amg::Vector3D iniPoint =  inpPer->position();
      Amg::Vector3D pmom=inpPer->momentum();
      //Track reference point ( some point on track provided initially, global frame )
      Amg::Vector3D refPoint(0.,0.,0.);
      if(TrkID>=0)refPoint = state.m_trkControl.at(TrkID).trkRefGlobPos;
      //
      Amg::Vector3D step  = (*endPoint) - iniPoint;
      //
      int Strategy = 0; if(TrkID>=0) Strategy = state.m_trkControl[TrkID].extrapolationType;
      //
      // Extrapolation for new track - no material at all
      //
      const TrackParameters *pntOnTrk=nullptr;
      if (TrkID < 0) {
        prtType = undefined;
        if (pmom.dot(step) > 0.) {
          endPer = m_extrapolator->extrapolateDirectly(ctx,
            *inpPer, surfEnd, alongMomentum, true, pion).release();
        } else {
          endPer = m_extrapolator->extrapolateDirectly(ctx,
            *inpPer, surfEnd, oppositeMomentum, true, pion).release();
        }
        return endPer;
      }
      pntOnTrk = dynamic_cast<const TrackParameters*>(
        state.m_trkControl.at(TrkID).TrkPnt);
      if (pntOnTrk == nullptr){
        return endPer;
      }
      prtType = pion; // Pion hypothesis is always used for extrapolation
      // Redefinition of starting point for extrapolation
      iniPoint = pntOnTrk->position();
      step = (*endPoint) - iniPoint;
 
      //
      // Extrapolation for first measured point strategy. Start from it and
      // always add material
      //
      if( Strategy == 0) {
        PropDirection dir = alongMomentum;
        if (pmom.dot(step) < 0) {
          dir = oppositeMomentum;
        }
        endPer = m_extrapolator->extrapolate(
          ctx, *pntOnTrk, surfEnd, dir, true, prtType, addNoise).release();
        return endPer;
      }
      //
      // Extrapolation for any measured point
      //
      if (Strategy == 1) {
        PropDirection dir = alongMomentum;
        MaterialUpdateMode mmode = addNoise;
        if (pmom.dot(step) < 0) {
          dir = oppositeMomentum;
          mmode = removeNoise;
        }
        endPer = m_extrapolator->extrapolate(
          ctx, *pntOnTrk, surfEnd, dir, true, prtType, mmode).release();
        return endPer;
      }
      //
      // Extrapolation for perigee and B-hit
      //
      if (Strategy == 2) {
        double Border = 25.;
        bool dirPositive = true;
        if (pmom.dot(step) < 0.)
          dirPositive = false;
        if ((*endPoint).perp() > Border && iniPoint.perp() > Border) {
          if (dirPositive) {
            endPer = m_extrapolator->extrapolate(
              ctx, *pntOnTrk, surfEnd, alongMomentum, true, prtType, addNoise).release();
          } else {
            endPer = m_extrapolator->extrapolate(ctx,
                                                 *pntOnTrk,
                                                 surfEnd,
                                                 oppositeMomentum,
                                                 true,
                                                 prtType,
                                                 removeNoise).release();
          }
          return endPer;
        }
        if ((*endPoint).perp() < Border && iniPoint.perp() < Border) {
          if (dirPositive) {
            endPer = m_extrapolator->extrapolate(ctx,
                                                 *pntOnTrk,
                                                 surfEnd,
                                                 alongMomentum,
                                                 true,
                                                 prtType,
                                                 removeNoise).release();
          } else {
            endPer = m_extrapolator->extrapolate(ctx,
                                                 *pntOnTrk,
                                                 surfEnd,
                                                 oppositeMomentum,
                                                 true,
                                                 prtType,
                                                 addNoise).release();
          }
          return endPer;
        }
        Amg::Transform3D trnsf;
        trnsf.setIdentity();
        CylinderSurface surfBorder(trnsf, Border, 3000.);
        if (iniPoint.perp() < Border) {
          tmpPer = m_extrapolator->extrapolate(ctx,
                                               *pntOnTrk,
                                               surfBorder,
                                               alongMomentum,
                                               true,
                                               prtType,
                                               removeNoise).release();
          if (tmpPer == nullptr) {
            return nullptr;
          }
          endPer = m_extrapolator->extrapolate(
            ctx, *tmpPer, surfEnd, alongMomentum, true, prtType, addNoise).release();
        } else {
          endPer = m_extrapolator->extrapolate(
            ctx, *pntOnTrk, surfEnd, oppositeMomentum, true, prtType, addNoise).release();
          return endPer;
        }
        delete tmpPer;
        return endPer;
      }
      return endPer;
  }
 
/*--------------------------------------------------------------------------------------*/
/* Extrapolation to line                                                                */
/*                                          */
/*    All points are in GLOBAL Atlas frame here!                    */
/*         DOESN't WORK FOR COMBINED TRACKS!                        */
/*--------------------------------------------------------------------------------------*/
  const TrackParameters* VKalExtPropagator::myExtrapToLine(long int TrkID,
                                                           const TrackParameters *inpPer,
                                                           Amg::Vector3D * endPoint,
                                                           StraightLineSurface  &lineTarget,
                                                           const IVKalState& istate) const
  {
      const TrkVKalVrtFitter::State& state = static_cast<const TrkVKalVrtFitter::State&> (istate);
      const EventContext& ctx = (state.m_eventContext)
                                  ? *(state.m_eventContext)
                                  : Gaudi::Hive::currentContext();
 
 
      const Trk::TrackParameters* endPer=nullptr;
      ParticleHypothesis prtType = muon;
//Initial point
      Amg::Vector3D iniPoint =  inpPer->position();
      Amg::Vector3D step  = (*endPoint) - iniPoint;
//
      int Strategy = 0; if(TrkID>=0) Strategy = state.m_trkControl[TrkID].extrapolationType;
//
// Extrapolation for new track - no material at all
//
      const TrackParameters *pntOnTrk=nullptr;
      if(TrkID<0){
        return endPer;
      }
        pntOnTrk=dynamic_cast<const TrackParameters*> (state.m_trkControl.at(TrkID).TrkPnt);
        if(!pntOnTrk) return endPer;
        //double inpMass=state.m_trkControl[TrkID].prtMass;
        //if(     inpMass >  0. && inpMass< 20.) {  prtType=electron; }  //VK  Disabled according to users request
        //else if(inpMass > 20. && inpMass<120.) {  prtType=muon; }      //    May be activated in future
        //else if(inpMass >120. && inpMass<200.) {  prtType=pion; }
        //else if(inpMass >200. && inpMass<700.) {  prtType=kaon; }
        //else if(inpMass >700. && inpMass<999.) {  prtType=proton; }
        //else {  prtType=undefined; }
        prtType=muon;                   // Muon hypothesis is always used for extrapolation
        iniPoint =  pntOnTrk->position();
        step  = (*endPoint) - iniPoint;
 
      Amg::Vector3D pmom=pntOnTrk->momentum();
//
// Extrapolation for first measured point strategy. Start from it and always add material
//
      if( Strategy == 0) {
        PropDirection dir=alongMomentum; if(pmom.dot(step)<0) dir=oppositeMomentum;
        endPer = m_extrapolator->extrapolate(ctx, *pntOnTrk, lineTarget, dir, true, prtType, addNoise).release();
        if (!endPer)
          endPer = m_extrapolator->extrapolateDirectly(ctx, *pntOnTrk, lineTarget, dir, true, prtType).release();
        return endPer;
      }
//
// Extrapolation for any measured point
//
      if( Strategy == 1 || Strategy == 2) {
         PropDirection dir=alongMomentum;  MaterialUpdateMode mmode=addNoise;
     if(pmom.dot(step)<0){ dir=oppositeMomentum; mmode=removeNoise;}
         endPer = m_extrapolator->extrapolate(ctx, *pntOnTrk, lineTarget, dir, true, prtType, mmode).release();
         return endPer;
      }
      return endPer;
  }
 
/*--------------------------------------------------------------------------------------*/
/* Simple extrapolation of neutral tracks                                               */
/*--------------------------------------------------------------------------------------*/
  const NeutralParameters* VKalExtPropagator::myExtrapNeutral( const NeutralParameters *inpPer,
                                                               Amg::Vector3D * endPoint) const
  {
      const Trk::NeutralParameters* endPer=nullptr;
//End surface
      PerigeeSurface surfEnd( *endPoint );
      endPer = m_extrapolator->extrapolate( *inpPer, surfEnd, anyDirection, true).release();
      return endPer;
  }
 
/*--------------------------------------------------------------------------------------*/
/*   xAOD method to find FirstMeasuredPoint on TrackParticle.               */
/*                                          */
/*    All points are in GLOBAL Atlas frame here!                    */
/*                                              */
/*   xAOD::TrackParticle Perigee is extrapolated to cylinder with radius of first hit   */
/*--------------------------------------------------------------------------------------*/
  const Perigee* VKalExtPropagator::myxAODFstPntOnTrk(const xAOD::TrackParticle* xprt) const
  {
    static const SG::ConstAccessor<float> radiusOfFirstHitAcc ("radiusOfFirstHit");
    if(!radiusOfFirstHitAcc.isAvailable (*xprt)) return nullptr;  // No radiusOfFirstHit on track
 
    const EventContext& ctx = Gaudi::Hive::currentContext();
    const Trk::Perigee*  mPer = &(xprt->perigeeParameters());
    Amg::Transform3D trnsf;
    trnsf.setIdentity();
    CylinderSurface surfacePntOnTrk( trnsf, xprt->radiusOfFirstHit(), 20000.);
    ParticleHypothesis prtType = pion;
 
    const TrackParameters *hitOnTrk =
          m_extrapolator->extrapolate(ctx,
                                      *mPer,
                                      surfacePntOnTrk,
                                      alongMomentum,
                                      true, prtType, removeNoise).release();
//std::cout<<" Radius="<<xprt->radiusOfFirstHit()<<" extrap="<<hitOnTrk<<'\n';
    if(hitOnTrk==nullptr)hitOnTrk=m_extrapolator->extrapolateDirectly(ctx,
                                                                      *mPer,
                                                                      surfacePntOnTrk,
                                                                      alongMomentum,
                                                                      true, prtType).release();
    if(hitOnTrk==nullptr)return nullptr;
 
    //convert result to Perigee
    PerigeeSurface surfacePerigee( hitOnTrk->position() );
    const TrackParameters *hitOnTrkPerig = m_extrapolator->extrapolate(ctx,
                                                                       *hitOnTrk,
                                                                       surfacePerigee).release();
    delete hitOnTrk;  // Delete temporary results
    if(hitOnTrkPerig==nullptr)return nullptr;
//std::cout<<" perig="<<(*hitOnTrkPerig)<<'\n';
    return dynamic_cast<const Perigee* > (hitOnTrkPerig);
  }
 
//--------------------------------------------------------------------------
//&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&&
//  Setting interface to setup VKalVrt InDet extrapolator
  void TrkVKalVrtFitter::setAthenaPropagator(const Trk::IExtrapolator*  Pnt)
  {
     // Save external propagator in VKalExtPropagator object and send it to TrkVKalVrtCore
//
     if(m_fitPropagator != nullptr) delete m_fitPropagator;
     m_fitPropagator = new VKalExtPropagator( this );
     m_fitPropagator->setPropagator(Pnt);
     m_InDetExtrapolator = Pnt;  // Pointer to InDet extrapolator
  }
 
}