DTDigitizer.cc

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// system include files
#include <memory>

//C++ headers
#include <cmath>

//Random generator
#include "FWCore/Utilities/interface/RandomNumberGenerator.h"
#include <CLHEP/Random/RandGaussQ.h>
#include <CLHEP/Random/RandFlat.h>

// Framework
#include "FWCore/Framework/interface/Frameworkfwd.h"
#include "FWCore/Framework/interface/EventSetup.h"
#include "FWCore/Framework/interface/Event.h"
#include "FWCore/ParameterSet/interface/ParameterSet.h"
#include "FWCore/Framework/interface/ESHandle.h"
#include "DataFormats/Common/interface/Handle.h"
#include "FWCore/ServiceRegistry/interface/Service.h"

// Geometry
#include "Geometry/Records/interface/MuonGeometryRecord.h"
#include "Geometry/DTGeometry/interface/DTGeometry.h"
#include "Geometry/DTGeometry/interface/DTLayer.h"
#include "Geometry/DTGeometry/interface/DTTopology.h"

#include "DataFormats/GeometryVector/interface/LocalPoint.h"

// Magnetic Field
#include "MagneticField/Engine/interface/MagneticField.h"
#include "MagneticField/Records/interface/IdealMagneticFieldRecord.h"

// SimHits
#include "SimDataFormats/TrackingHit/interface/PSimHitContainer.h"
#include "SimDataFormats/TrackingHit/interface/PSimHit.h"
#include "SimDataFormats/CrossingFrame/interface/CrossingFrame.h"
#include "SimDataFormats/CrossingFrame/interface/MixCollection.h"

// Digis
#include "DataFormats/DTDigi/interface/DTDigiCollection.h"
#include "DataFormats/MuonDetId/interface/DTWireId.h"
#include "DataFormats/MuonDetId/interface/DTLayerId.h"

// DTDigitizer
#include "SimMuon/DTDigitizer/interface/DTDigiSyncFactory.h"
#include "SimMuon/DTDigitizer/interface/DTDigiSyncBase.h"

#include "SimMuon/DTDigitizer/src/DTDriftTimeParametrization.h"
#include "SimMuon/DTDigitizer/src/DTDigitizer.h"

// namespaces
using namespace edm;
using namespace std;

// Constructor
DTDigitizer::DTDigitizer(const ParameterSet& conf_) {
  
  // Set verbose output
  debug=conf_.getUntrackedParameter<bool>("debug"); 
    
  if (debug) cout<<"Creating a DTDigitizer"<<endl;
  
  //register the Producer with a label
  //produces<DTDigiCollection>("MuonDTDigis"); // FIXME: Do I pass it by ParameterSet?
  produces<DTDigiCollection>(); // FIXME: Do I pass it by ParameterSet?
  //  produces<DTDigiSimLinkCollection>("MuonDTDigiSimLinks");
  produces<DTDigiSimLinkCollection>();
  
  //Parameters:

  // build digis only for mu hits (for debug purposes) 
  onlyMuHits=conf_.getParameter<bool>("onlyMuHits");
  
  // interpolate parametrization function
  interpolate=conf_.getParameter<bool>("interpolate");
  
  // Velocity of signal propagation along the wire (cm/ns)
  // For the default value
  // cfr. CMS-IN 2000-021:   (2.56+-0.17)x1e8 m/s
  //      CMS NOTE 2003-17:  (0.244)  m/ns
  vPropWire=conf_.getParameter<double>("vPropWire"); //24.4

  // Dead time for signals on the same wire (number from M. Pegoraro)  
  deadTime=conf_.getParameter<double>("deadTime"); //150
  
  // further configurable smearing
  smearing=conf_.getParameter<double>("Smearing"); // 3.

  // Sync Algo
  syncName = conf_.getParameter<string>("SyncName");
  theSync = DTDigiSyncFactory::get()->create(syncName,conf_.getParameter<ParameterSet>("pset"));

  // Debug flag to switch to the Ideal model
  // it uses a constant drift velocity and doesn't set any external delay
  IdealModel = conf_.getParameter<bool>("IdealModel");

  // Constant drift velocity needed by the above flag
  if(IdealModel)
    theConstVDrift = conf_.getParameter<double>("IdealModelConstantDriftVelocity"); // 55 um/ns
  else theConstVDrift = 55.;

  // get random engine
  edm::Service<edm::RandomNumberGenerator> rng;
  if ( ! rng.isAvailable()) {
    throw cms::Exception("Configuration")
      << "RandomNumberGeneratorService for DTDigitizer missing in cfg file";
  }
  theGaussianDistribution = new CLHEP::RandGaussQ(rng->getEngine()); 
  theFlatDistribution = new CLHEP::RandFlat(rng->getEngine(), 0, 1); 

  // MultipleLinks=false ==> one-to-one correspondence between digis and SimHits 
  MultipleLinks = conf_.getParameter<bool>("MultipleLinks");
  // MultipleLinks=true ==> association of SimHits within a time window LinksTimeWindow 
  // (of the order of the resolution)
  LinksTimeWindow = conf_.getParameter<double>("LinksTimeWindow"); // (10 ns)

  //Name of Collection used for create the XF 
  collection_for_XF = conf_.getParameter<std::string>("InputCollection");

  //String to choice between ideal (the deafult) and (mis)aligned geometry for the digitization step 
  geometryType = conf_.getParameter<std::string>("GeometryType");
}

// Destructor
DTDigitizer::~DTDigitizer(){
  delete theGaussianDistribution;
  delete theFlatDistribution;
}

// method called to produce the data
void DTDigitizer::produce(Event& iEvent, const EventSetup& iSetup){
  if(debug)
    cout << "--- Run: " << iEvent.id().run()
     << " Event: " << iEvent.id().event() << endl;
  
  //************ 1 ***************
   // create the container for the SimHits
  //  Handle<PSimHitContainer> simHits; 
  //  iEvent.getByLabel("g4SimHits","MuonDTHits",simHits);
    
  // use MixCollection instead of the previous
  Handle<CrossingFrame<PSimHit> > xFrame;
  iEvent.getByLabel("mix",collection_for_XF,xFrame);
  
  auto_ptr<MixCollection<PSimHit> > 
    simHits( new MixCollection<PSimHit>(xFrame.product()) );

   // create the pointer to the Digi container
  auto_ptr<DTDigiCollection> output(new DTDigiCollection());
   // pointer to the DigiSimLink container
  auto_ptr<DTDigiSimLinkCollection> outputLinks(new DTDigiSimLinkCollection());
  
  // Muon Geometry
  ESHandle<DTGeometry> muonGeom;
  iSetup.get<MuonGeometryRecord>().get(geometryType,muonGeom);

  // Magnetic Field  
  ESHandle<MagneticField> magnField;
  iSetup.get<IdealMagneticFieldRecord>().get(magnField);

  //************ 2 ***************

  // These are sorted by DetId, i.e. by layer and then by wire #
  //  map<DTDetId, vector<const PSimHit*> > wireMap;     
  DTWireIdMap wireMap;     
  
  for(MixCollection<PSimHit>::MixItr simHit = simHits->begin();
       simHit != simHits->end(); simHit++){
    
    // Create the id of the wire, the simHits in the DT known also the wireId
 
    DTWireId wireId( (*simHit).detUnitId() );
    // Fill the map
    wireMap[wireId].push_back(&(*simHit));
  }
  
  pair<float,bool> time(0.,false);

  //************ 3 ***************
  // Loop over the wires
  for(DTWireIdMapConstIter wire = wireMap.begin(); wire!=wireMap.end(); wire++){
    // SimHit Container associated to the wire
    const vector<const PSimHit*> & vhit = (*wire).second; 
    if(vhit.size()!=0) {
      TDContainer tdCont; // It is a vector<pair<const PSimHit*,float> >;
      
      //************ 4 ***************
      DTWireId wireId = (*wire).first;

      //const DTLayer* layer = dynamic_cast< const DTLayer* > (muonGeom->idToDet(wireId.layerId()));
      const DTLayer* layer = muonGeom->layer(wireId.layerId()); 

      // Loop on the hits of this wire    
      for (vector<const PSimHit*>::const_iterator hit=vhit.begin();
       hit != vhit.end(); hit++){
    //************ 5 ***************
    LocalPoint locPos = (*hit)->localPosition();

    const LocalVector BLoc=layer->surface().toLocal(magnField->inTesla(layer->surface().toGlobal(locPos)));

    time = computeTime(layer, wireId, *hit, BLoc); 

    //************ 6 ***************
    if (time.second) {
      tdCont.push_back(make_pair((*hit),time.first));
    } else {
      if (debug) cout << "hit discarded" << endl;
    }
      }

      //************ 7 ***************

      // the loading must be done by layer but
      // the digitization must be done by wire (in order to take into account the dead time)

      storeDigis(wireId,tdCont,*output,*outputLinks);
    }
    
  }

  //************ 8 ***************  
  // Load the Digi Container in the Event
  //iEvent.put(output,"MuonDTDigis");
  iEvent.put(output);
  iEvent.put(outputLinks);

}

pair<float,bool> DTDigitizer::computeTime(const DTLayer* layer, const DTWireId &wireId, 
                      const PSimHit *hit, const LocalVector &BLoc){ 
 
  LocalPoint entryP = hit->entryPoint();
  LocalPoint exitP = hit->exitPoint();
  int partType = hit->particleType();

  const DTTopology &topo = layer->specificTopology();

  // Pay attention: in CMSSW the rf of the SimHit is in the layer's rf
  
  if(debug)  cout<<"Hit local entry point: "<<entryP<<endl
         <<"Hit local exit point: "<<exitP<<endl;

  float xwire = topo.wirePosition(wireId.wire()); 
  float xEntry = entryP.x() - xwire;
  float xExit  = exitP.x() - xwire;

  if(debug) cout<<"wire position: "<<xwire
        <<" x entry in cell rf: "<<xEntry
        <<" x exit in cell rf: "<<xExit<<endl;
  
  DTTopology::Side entrySide = topo.onWhichBorder(xEntry,entryP.y(),entryP.z());
  DTTopology::Side exitSide  = topo.onWhichBorder(xExit,exitP.y(),exitP.z());

   if (debug) dumpHit(hit, xEntry, xExit,topo);

  // The bolean is used to flag the drift time computation
  pair<float,bool> driftTime(0.,false);  

  // if delta in gas->ignore, since it is included in the parametrisation.
  // FIXME: should check that it is actually a delta ray produced by a nearby
  // muon hit. 

  if (partType == 11 && entrySide == DTTopology::none) {
     if (debug) cout << "    e- hit in gas; discarding " << endl;
    return driftTime;
  }

  float By = BLoc.y();
  float Bz = BLoc.z();

  // Radius and sagitta according to direction of momentum
  // (just for printing)
  // NOTE: in cmsim, d is always taken // pHat!
  LocalVector d = (exitP-entryP);
  LocalVector pHat = hit->localDirection().unit();
  LocalVector hHat = (d.cross(pHat.cross(d))).unit();
  float cosAlpha = hHat.dot(pHat);
  float sinAlpha = sqrt(1.-cosAlpha*cosAlpha);
  float radius_P = (d.mag())/(2.*cosAlpha);
  float sagitta_P = radius_P*(1.-sinAlpha);

  // Radius, sagitta according to field bending
  // (just for printing)
  float halfd = d.mag()/2.;
  float BMag = BLoc.mag();
  LocalVector pT = (pHat - (BLoc.unit()*pHat.dot(BLoc.unit())))*(hit->pabs());
  float radius_B = (pT.mag()/(0.3*BMag))*100.;
  float sagitta_B;
  if (radius_B > halfd) {
    sagitta_B = radius_B - sqrt(radius_B*radius_B - halfd*halfd);
  } else {
    sagitta_B = radius_B;
  }

  // cos(delta), delta= angle between direction at entry and hit segment
  // (just for printing)
  float delta = pHat.dot(d.unit());
  if (debug) cout << "   delta                 = " << delta  << endl
          << "   cosAlpha              = " << cosAlpha << endl
          << "   sinAlpha              = " << sinAlpha << endl
          << "   pMag                  = " << pT.mag() << endl
          << "   bMag                  = " << BMag << endl
          << "   pT                    = " << pT << endl
          << "   halfd                 = " << halfd << endl
          << "   radius_P  (cm)        = " << radius_P << endl
          << "   sagitta_P (um)        = " << sagitta_P*10000. << endl
          << "   radius_B  (cm)        = " << radius_B << endl
          << "   sagitta_B (um)        = " << sagitta_B*10000. << endl;

  // Select cases where parametrization can not be used.
  bool noParametrisation = 
    ( ( entrySide == DTTopology::none || exitSide == DTTopology::none ) // case # 2,3,8,9 or 11
      || (entrySide == exitSide)                   // case # 4 or 10
      || ((entrySide == DTTopology::xMin && exitSide == DTTopology::xMax) || 
      (entrySide == DTTopology::xMax && exitSide == DTTopology::xMin)) // Hit is case # 7
      );

  // FIXME: now, debug warning only; consider treating those 
  // with TM algo. 
  if ( delta < 0.99996 // Track is not straight. FIXME: use sagitta?
       && (noParametrisation == false)) {
    if (debug) cout << "*** WARNING: hit is not straight, type = " << partType << endl;
  }

  //************ 5A ***************

  if (!noParametrisation) {
   
    LocalVector dir = hit->momentumAtEntry(); // ex Measurement3DVector dir = hit->measurementDirection(); //FIXME?
    float theta = atan(dir.x()/-dir.z())*180/M_PI;

    // FIXME: use dir if M.S. is included as GARFIELD option...
    //        otherwise use hit segment dirction.
    //    LocalVector dir0 = (exitP-entryP).unit();
    //    float theta = atan(dir0.x()/-dir0.z())*180/M_PI;
    float x;

    Local3DPoint pt = hit->localPosition();  //ex Measurement3DPoint pt = hit->measurementPosition(); // FIXME?
     
    if(fabs(pt.z()) < 0.002) { 
      // hit center within 20 um from z=0, no need to extrapolate.
      x = pt.x() - xwire;
    } else {
      x = xEntry - (entryP.z()*(xExit-xEntry))/(exitP.z()-entryP.z());
    }

    if(IdealModel) return make_pair(fabs(x)/theConstVDrift,true);
    else driftTime = driftTimeFromParametrization(x, theta, By, Bz);

  }

 
  if ((driftTime.second)==false) {
    // Parametrisation not applicable, or failed. Use time map.
    driftTime = driftTimeFromTimeMap();
  }
  
  //************ 5B ***************

  // Signal propagation, TOF etc.
  if (driftTime.second) {
    driftTime.first += externalDelays(layer,wireId,hit);
  }
  return driftTime;
} 

//************ 5A ***************

pair<float,bool> DTDigitizer::driftTimeFromParametrization(float x, float theta, float By, float Bz) const {

  // Convert from CMSSW frame/units r.f. to parametrization ones.
  x *= 10.;  //cm -> mm 

  // FIXME: Current parametrisation can extrapolate above 21 mm,
  // however a detailed study is needed before using this.
   if (fabs(x) > 21.) {
     if (debug) cout << "*** WARNING: parametrisation: x out of range = "
             << x << ", skipping" << endl;
     return pair<float,bool>(0.f,false);
  }

  // Different r.f. of the parametrization:
  // X_par = X_ORCA; Y_par=Z_ORCA; Z_par = -Y_ORCA  

  float By_par = Bz;  // Bnorm
  float Bz_par = -By; // Bwire
  float theta_par = theta;

  // Parametrisation uses interpolation up to |theta|=45 deg,
  // |Bwire|=0.4, |Bnorm|=0.75; extrapolation above.
  if (fabs(theta_par)>45.) {
    if (debug) cout << "*** WARNING: extrapolating theta > 45: "
            << theta << endl;
    // theta_par = min(fabs(theta_par),45.f)*((theta_par<0.)?-1.:1.);
  }
  if (fabs(By_par)>0.75) {
    if (debug) cout << "*** WARNING: extrapolating Bnorm > 0.75: "
            << By_par << endl;
    // By_par = min(fabs(By_par),0.75f)*((By_par<0.)?-1.:1.);
  }
  if (fabs(Bz_par)>0.4) {
    if (debug) cout << "*** WARNING: extrapolating Bwire >0.4: "
            << Bz_par << endl;
    // Bz_par = min(fabs(Bz_par),0.4)*((Bz_par<0.)?-1.:1.);
  }

  DTDriftTimeParametrization::drift_time DT;
  static DTDriftTimeParametrization par;
  unsigned short flag = par.MB_DT_drift_time (x, theta_par, By_par, Bz_par, 0, &DT, interpolate);

  if (debug) {
    cout << "    Parametrisation: x, theta, Bnorm, Bwire = "
     << x << " " <<  theta_par << " " << By_par << " " << Bz_par << endl
     << "  time=" << DT.t_drift
     << "  sigma_m=" <<  DT.t_width_m
     << "  sigma_p=" <<  DT.t_width_p << endl;
    if (flag!=1) {
      cout << "*** WARNING: call to parametrisation failed" << endl;
      return pair<float,bool>(0.f,false); 
    }
  }

  // Double half-gaussian smearing
  float time = asymGausSmear(DT.t_drift, DT.t_width_m, DT.t_width_p);

  // Do not allow the smearing to lead to negative values
  time = max(time,0.f);

  // Apply a Gaussian smearing to account for electronic effects (cf. 2004 TB analysis)
  // The width of the Gaussian can be configured with the "Smearing" parameter

  double u = theGaussianDistribution->fire(0.,smearing);
  time += u;

  if (debug) cout << "  drift time = " << time << endl;
  
  return pair<float,bool>(time,true); 
}

float DTDigitizer::asymGausSmear(double mean, double sigmaLeft, double sigmaRight) const {

  double f = sigmaLeft/(sigmaLeft+sigmaRight);
  double t;

  if (theFlatDistribution->fire() <= f) {
    t = theGaussianDistribution->fire(mean,sigmaLeft);
    t = mean - fabs(t - mean);
  } else {
    t = theGaussianDistribution->fire(mean,sigmaRight);
    t = mean + fabs(t - mean);
  }
  return static_cast<float>(t);
}

pair<float,bool> DTDigitizer::driftTimeFromTimeMap() const {
  // FIXME: not yet implemented.
  if (debug) cout << "   TimeMap " << endl;
  return pair<float,bool>(0.,false);
}

//************ 5B ***************

float DTDigitizer::externalDelays(const DTLayer* layer,
                  const DTWireId &wireId, 
                  const PSimHit *hit) const {
  
  // Time of signal propagation along wire.
  
  float wireCoord = hit->localPosition().y();
  float halfL     = (layer->specificTopology().cellLenght())/2.;
  float propgL = halfL - wireCoord; // the FE is always located at the pos coord.

  float propDelay = propgL/vPropWire;

  // Real TOF.
  float tof = hit->tof();  

  // Delays and t0 according to theSync

  double sync= theSync->digitizerOffset(&wireId,layer);


  if (debug) {
    cout << "    propDelay =" << propDelay
     << "; TOF=" << tof
     << "; sync= " << sync
     << endl;
  }
  
  return propDelay + tof + sync;
}


// accumulate digis by layer

void DTDigitizer::storeDigis(DTWireId &wireId, 
                 TDContainer &hits,
                 DTDigiCollection &output, DTDigiSimLinkCollection &outputLinks){

  //************ 7A ***************

  // sort signal times
  sort(hits.begin(),hits.end(),hitLessT());

  //************ 7B ***************

  float wakeTime = -999999.0;
  float resolTime = -999999.0;
  int digiN = -1; // Digi identifier within the cell (for multiple digis)
  DTDigi digi;

  // loop over signal times and drop signals inside dead time
  for ( TDContainer::const_iterator hit = hits.begin() ; hit != hits.end() ; 
    hit++ ) {

    if (onlyMuHits && abs((*hit).first->particleType())!=13) continue;

    //************ 7C ***************
    
    float time = (*hit).second;
    if ( time > wakeTime ) {
      // Note that digi is constructed with a float value (in ns)
      int wireN = wireId.wire();
      digiN++;
      digi = DTDigi(wireN, time, digiN);

      // Add association between THIS digi and the corresponding SimTrack
      unsigned int SimTrackId = (*hit).first->trackId();
      EncodedEventId evId = (*hit).first->eventId();
      DTDigiSimLink digisimLink(wireN, digiN, time, SimTrackId, evId);

      if(debug) {
    cout<<endl<<"---- DTDigitizer ----"<<endl;
    cout<<"wireId: "<<wireId<<endl;
    cout<<"sim. time = "<<time<<endl;
    cout<<"digi number = "<< digi.number()<<", digi time = "<<digi.time()
        <<", linked to SimTrack Id = "<<SimTrackId<<endl;
      }

      //************ 7D ***************
      if(digi.countsTDC() < pow(2.,16)){
    DTLayerId layerID = wireId.layerId();  //taking the layer in which reside the wire
        output.insertDigi(layerID, digi); // ordering Digis by layer
        outputLinks.insertDigi(layerID, digisimLink);
    wakeTime = time + deadTime;
    resolTime = time + LinksTimeWindow;
      } 
      else {
    digiN--;
      }
    }
    else if (MultipleLinks && time < resolTime){
      int wireN = wireId.wire();
      unsigned int SimTrackId = (*hit).first->trackId();
      EncodedEventId evId = (*hit).first->eventId();
      DTDigiSimLink digisimLink(wireN, digiN, time, SimTrackId, evId);
      DTLayerId layerID = wireId.layerId(); 
      outputLinks.insertDigi(layerID, digisimLink);

      if(debug) { 
    cout<<"\nAdded multiple link: \n"
        <<"digi number = "<<digi.number()<<", digi time = "<<digi.time()<<" (sim. time = "<<time<<")"
        <<", linked to SimTrack Id = "<<SimTrackId<<endl;
      }
    }
  }
  
}

void DTDigitizer::dumpHit(const PSimHit * hit,
                          float xEntry, float xExit,
                          const DTTopology &topo) {
  
  LocalPoint entryP = hit->entryPoint();
  LocalPoint exitP = hit->exitPoint();
  
  DTTopology::Side entrySide = topo.onWhichBorder(xEntry,entryP.y(),entryP.z());
  DTTopology::Side exitSide  = topo.onWhichBorder(xExit,exitP.y(),exitP.z());
  //  ProcessTypeEnumerator pTypes;
  
  cout << endl
       << "------- SimHit: " << endl
       << "   Particle type         = " << hit->particleType() << endl
       << "   process type          = " << hit->processType() << endl
       << "   process type          = " << hit->processType() << endl
    // << "   packedTrackId         = " << hit->packedTrackId() << endl
       << "   trackId               = " << hit->trackId() << endl // new,is the same as the
                                                                  // previous?? FIXME-Check
       << "   |p|                   = " << hit->pabs() << endl
       << "   Energy loss           = " << hit->energyLoss() << endl
    // << "   timeOffset            = " << hit->timeOffset() << endl
    // << "   measurementPosition   = " << hit->measurementPosition() << endl
    // << "   measurementDirection  = " << hit->measurementDirection() << endl      //FIXME
       << "   localDirection        = " << hit->momentumAtEntry().unit() << endl    //FIXME is it a versor?
       << "   Entry point           = " << entryP << " cell x = " << xEntry << endl
       << "   Exit point            = " << exitP << " cell x = " << xExit << endl
       << "   DR =                  = " << (exitP-entryP).mag() << endl
       << "   Dx =                  = " << (exitP-entryP).x() << endl
       << "   Cell w,h,l            = (" << topo.cellWidth()
       << " , " << topo.cellHeight() 
       << " , " << topo.cellLenght() << ") cm" << endl
       << "   DY entry from edge    = " << topo.cellLenght()/2.-fabs(entryP.y())
       << "   DY exit  from edge    = " << topo.cellLenght()/2.-fabs(exitP.y())
       << "   entrySide = "  << (int)entrySide
       << " ; exitSide = " << (int)exitSide << endl;

}