CbmLitNearestHitTofMerger.cxx

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/* Copyright (C) 2013-2016 GSI/JINR-LIT, Darmstadt/Dubna
   SPDX-License-Identifier: GPL-3.0-only
   Authors: Andrey Lebedev [committer] */
 
#include "finder/CbmLitNearestHitTofMerger.h"
 
#include "data/CbmLitHit.h"
#include "data/CbmLitTofTrack.h"
#include "data/CbmLitTrack.h"
#include "data/CbmLitTrackParam.h"
#include "interface/CbmLitTrackPropagator.h"
#include "interface/CbmLitTrackUpdate.h"
#include "utils/CbmLitMath.h"
 
#include <iostream>
#include <map>
 
using std::map;
 
CbmLitNearestHitTofMerger::CbmLitNearestHitTofMerger()
  : fFieldPropagator()
  , fLinePropagator()
  , fFilter()
  , fPDG(211)
  , fChiSqCut(25.)
{
}
 
CbmLitNearestHitTofMerger::~CbmLitNearestHitTofMerger() {}
 
LitStatus CbmLitNearestHitTofMerger::DoMerge(HitPtrVector& hits, TrackPtrVector& tracks, TofTrackPtrVector& tofTracks)
{
  // First find hit with minimum Z position and build map from Z hit position
  // to track parameter to improve the calculation speed.
  litfloat zMin = std::numeric_limits<litfloat>::max();
  map<litfloat, CbmLitTrackParam> zParamMap;
  for (HitPtrIterator it = hits.begin(); it != hits.end(); it++) {
    const CbmLitHit* hit   = *it;
    zMin                   = std::min(zMin, hit->GetZ());
    zParamMap[hit->GetZ()] = CbmLitTrackParam();
  }
 
  // Loop over input tracks
  for (TrackPtrIterator it = tracks.begin(); it != tracks.end(); it++) {
    CbmLitTrack* track = *it;
    if (track->GetQuality() != kLITGOODMERGE) {
      continue;
    }
    CbmLitTrackParam par(*track->GetParamLast());
 
    // Extrapolate track minimum Z position of hit using magnetic field propagator.
    if (fFieldPropagator->Propagate(&par, zMin, fPDG) == kLITERROR) {
      continue;  // skip this track if its propagation failed
    }
 
    // Extrapolate track parameters to each Z position in the map.
    // This is done to improve calculation speed.
    // In case of planar TOF geometry only 1 track extrapolation is required,
    // since all hits located at the same Z.
    for (map<litfloat, CbmLitTrackParam>::iterator it2 = zParamMap.begin(); it2 != zParamMap.end(); it2++) {
      (*it2).second = par;
      fLinePropagator->Propagate(&(*it2).second, (*it2).first, fPDG);
    }
 
    // Loop over hits
    litfloat minChiSq       = std::numeric_limits<litfloat>::max();  // minimum chi-square of hit
    const CbmLitHit* minHit = NULL;                                  // Pointer to hit with minimum chi-square
    CbmLitTrackParam minPar;                                         // Track parameters for closest hit
    for (HitPtrIterator it = hits.begin(); it != hits.end(); it++) {
      const CbmLitHit* hit = *it;
      if (zParamMap.find(hit->GetZ()) == zParamMap.end()) {  // This should never happen
        std::cout << "-E- CbmLitNearestHitTofMerger::DoMerge: Z position " << hit->GetZ()
                  << " not found in map. Something is wrong.\n";
        assert(0);
      }
      CbmLitTrackParam tpar(zParamMap[hit->GetZ()]);
      litfloat chi = 1.e10;
      fFilter->Update(&tpar, hit, chi);
 
      // Check if hit is inside validation gate.
      if (fChiSqCut >= 0. && chi >= fChiSqCut) {
        continue;
      }
 
      if (chi < minChiSq) {  // Check if hit is closer to the track.
        minChiSq = chi;
        minHit   = hit;
        minPar   = tpar;
      }
    }
 
    if (minHit != NULL) {  // Check if hit was added
      //Create new TOF track
      CbmLitTofTrack* tofTrack = new CbmLitTofTrack();
      tofTrack->SetTrack(track);
      tofTrack->SetHit(minHit);
      tofTrack->SetTrackParam(&minPar);
      tofTrack->SetDistance(minChiSq);
      tofTracks.push_back(tofTrack);
    }
  }
  return kLITSUCCESS;
}