DTDigitizer.cc

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// system include files
#include <memory>

// C++ headers
#include <cmath>

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

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

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

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

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

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

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

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

// namespaces
using namespace edm;
using namespace std;

// Constructor
DTDigitizer::DTDigitizer(const ParameterSet &conf_)
    :  // Sync Algo
      theSync{DTDigiSyncFactory::get()->create(conf_.getParameter<string>("SyncName"),
                                               conf_.getParameter<ParameterSet>("pset"))} {
  // Set verbose output
  debug = conf_.getUntrackedParameter<bool>("debug");

  if (debug)
    LogPrint("DTDigitizer") << "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.

  // 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";
  }

  // 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
  mix_ = conf_.getParameter<std::string>("mixLabel");
  collection_for_XF = conf_.getParameter<std::string>("InputCollection");
  cf_token = consumes<CrossingFrame<PSimHit>>(edm::InputTag(mix_, collection_for_XF));

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

// method called to produce the data
void DTDigitizer::produce(Event &iEvent, const EventSetup &iSetup) {
  edm::Service<edm::RandomNumberGenerator> rng;
  CLHEP::HepRandomEngine *engine = &rng->getEngine(iEvent.streamID());

  if (debug)
    LogPrint("DTDigitizer") << "--- 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.getByToken(cf_token, xFrame);

  unique_ptr<MixCollection<PSimHit>> simHits(new MixCollection<PSimHit>(xFrame.product()));

  // create the pointer to the Digi container
  unique_ptr<DTDigiCollection> output(new DTDigiCollection());
  // pointer to the DigiSimLink container
  unique_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.empty()) {
      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, engine);

        //************ 6 ***************
        if (time.second) {
          tdCont.push_back(make_pair((*hit), time.first));
        } else {
          if (debug)
            LogPrint("DTDigitizer") << "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(std::move(output),"MuonDTDigis");
  iEvent.put(std::move(output));
  iEvent.put(std::move(outputLinks));
}

pair<float, bool> DTDigitizer::computeTime(const DTLayer *layer,
                                           const DTWireId &wireId,
                                           const PSimHit *hit,
                                           const LocalVector &BLoc,
                                           CLHEP::HepRandomEngine *engine) {
  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)
    LogPrint("DTDigitizer") << "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)
    LogPrint("DTDigitizer") << "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)
      LogPrint("DTDigitizer") << "    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)
    LogPrint("DTDigitizer") << "   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)
      LogPrint("DTDigitizer") << "*** 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, engine);
  }

  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, CLHEP::HepRandomEngine *engine) 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)
      LogPrint("DTDigitizer") << "*** 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)
      LogPrint("DTDigitizer") << "*** 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)
      LogPrint("DTDigitizer") << "*** 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)
      LogPrint("DTDigitizer") << "*** 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 const DTDriftTimeParametrization par;
  unsigned short flag = par.MB_DT_drift_time(x, theta_par, By_par, Bz_par, 0, &DT, interpolate);

  if (debug) {
    LogPrint("DTDigitizer") << "    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) {
      LogPrint("DTDigitizer") << "*** 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, engine);

  // 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 = CLHEP::RandGaussQ::shoot(engine, 0., smearing);
  time += u;

  if (debug)
    LogPrint("DTDigitizer") << "  drift time = " << time << endl;

  return pair<float, bool>(time, true);
}

float DTDigitizer::asymGausSmear(double mean,
                                 double sigmaLeft,
                                 double sigmaRight,
                                 CLHEP::HepRandomEngine *engine) const {
  double f = sigmaLeft / (sigmaLeft + sigmaRight);
  double t;

  if (CLHEP::RandFlat::shoot(engine) <= f) {
    t = CLHEP::RandGaussQ::shoot(engine, mean, sigmaLeft);
    t = mean - fabs(t - mean);
  } else {
    t = CLHEP::RandGaussQ::shoot(engine, mean, sigmaRight);
    t = mean + fabs(t - mean);
  }
  return static_cast<float>(t);
}

pair<float, bool> DTDigitizer::driftTimeFromTimeMap() const {
  // FIXME: not yet implemented.
  if (debug)
    LogPrint("DTDigitizer") << "   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) {
    LogPrint("DTDigitizer") << "    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) {
        LogPrint("DTDigitizer") << endl << "---- DTDigitizer ----" << endl;
        LogPrint("DTDigitizer") << "wireId: " << wireId << endl;
        LogPrint("DTDigitizer") << "sim. time = " << time << endl;
        LogPrint("DTDigitizer") << "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) {
        LogPrint("DTDigitizer") << "\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;

  LogPrint("DTDigitizer") << 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;
}