#include <TransientInitialStateEstimator.h>

Public Types
typedef TrajectoryStateOnSurface	TSOS

Public Member Functions
std::pair< TrajectoryStateOnSurface, const GeomDet * >	innerState (const Trajectory &traj, bool doBackFit=true) const

void	setEventSetup (const edm::EventSetup &es, const TkClonerImpl &hc)

	TransientInitialStateEstimator (const edm::ParameterSet &conf)

Private Attributes
TkClonerImpl	theHitCloner

const int	theNumberMeasurementsForFit

const Propagator *	thePropagatorAlong

const std::string	thePropagatorAlongName

const Propagator *	thePropagatorOpposite

const std::string	thePropagatorOppositeName

Detailed Description

Computes the trajectory state to be used as a starting state for the track fit from the vector of hits. The parameters of this state are close to the final fit parameters. The error matrix is enlarged in order not to bias the track fit.

Definition at line 23 of file TransientInitialStateEstimator.h.

Member Typedef Documentation

◆ TSOS

typedef TrajectoryStateOnSurface TransientInitialStateEstimator::TSOS

Definition at line 25 of file TransientInitialStateEstimator.h.

Constructor & Destructor Documentation

◆ TransientInitialStateEstimator()

TransientInitialStateEstimator::TransientInitialStateEstimator ( const edm::ParameterSet & conf )

Definition at line 21 of file TransientInitialStateEstimator.cc.

     : thePropagatorAlongName(conf.getParameter<std::string>("propagatorAlongTISE")),
       thePropagatorOppositeName(conf.getParameter<std::string>("propagatorOppositeTISE")),
       thePropagatorAlong(nullptr),
       thePropagatorOpposite(nullptr),
       theNumberMeasurementsForFit(conf.getParameter<int>("numberMeasurementsForFit")) {}

Member Function Documentation

◆ innerState()

std::pair< TrajectoryStateOnSurface, const GeomDet * > TransientInitialStateEstimator::innerState	(	const Trajectory &	traj,
		bool	doBackFit = `true`
	)		const

Definition at line 40 of file TransientInitialStateEstimator.cc.

                                                                                                                      {
   if (!doBackFit && traj.firstMeasurement().forwardPredictedState().isValid()) {
     LogDebug("TransientInitialStateEstimator")
         << "a backward fit will not be done. assuming that the state on first measurement is OK";
     TSOS firstStateFromForward = traj.firstMeasurement().forwardPredictedState();
     firstStateFromForward.rescaleError(100.);
     return std::pair<TrajectoryStateOnSurface, const GeomDet*>(std::move(firstStateFromForward),
                                                                traj.firstMeasurement().recHit()->det());
   }
   if (!doBackFit) {
     LogDebug("TransientInitialStateEstimator")
         << "told to not do a back fit, but the forward state of the first measurement is not valid. doing a back fit.";
   }
  
   int nMeas = traj.measurements().size();
   int lastFitted = theNumberMeasurementsForFit >= 0 ? theNumberMeasurementsForFit : nMeas;
   if (nMeas - 1 < lastFitted)
     lastFitted = nMeas - 1;
  
   auto const& measvec = traj.measurements();
   TransientTrackingRecHit::ConstRecHitContainer firstHits;
  
   bool foundLast = false;
   int actualLast = -99;
  
   for (int i = lastFitted; i >= 0; i--) {
     if (measvec[i].recHit()->det()) {
       if (!foundLast) {
         actualLast = i;
         foundLast = true;
       }
       firstHits.push_back(measvec[i].recHit());
     }
   }
   TSOS startingState = measvec[actualLast].updatedState();
   startingState.rescaleError(100.);
  
   // avoid cloning...
   KFUpdator const aKFUpdator;
   Chi2MeasurementEstimator const aChi2MeasurementEstimator(100., 3);
   KFTrajectoryFitter backFitter(
       thePropagatorAlong, &aKFUpdator, &aChi2MeasurementEstimator, firstHits.size(), nullptr, &theHitCloner);
  
   PropagationDirection backFitDirection = traj.direction() == alongMomentum ? oppositeToMomentum : alongMomentum;
  
   // only direction matters in this contest
   TrajectorySeed fakeSeed(PTrajectoryStateOnDet(), edm::OwnVector<TrackingRecHit>(), backFitDirection);
  
   Trajectory&& fitres = backFitter.fitOne(
       fakeSeed, firstHits, startingState, traj.nLoops() > 0 ? TrajectoryFitter::looper : TrajectoryFitter::standard);
  
   LogDebug("TransientInitialStateEstimator")
       << "using a backward fit of :" << firstHits.size() << " hits, starting from:\n"
       << startingState << " to get the estimate of the initial state of the track.";
  
   if (!fitres.isValid()) {
     LogDebug("TransientInitialStateEstimator") << "FitTester: first hits fit failed!";
     return std::pair<TrajectoryStateOnSurface, const GeomDet*>();
   }
  
   TrajectoryMeasurement const& firstMeas = fitres.lastMeasurement();
  
   // magnetic field can be different!
   TSOS firstState(firstMeas.updatedState().localParameters(),
                   firstMeas.updatedState().localError(),
                   firstMeas.updatedState().surface(),
                   thePropagatorAlong->magneticField());
  
   // TSOS & firstState = const_cast<TSOS&>(firstMeas.updatedState());
  
   // this fails in case of zero field? (for sure for beamhalo reconstruction)
   // assert(thePropagatorAlong->magneticField()==firstState.magneticField());
  
   firstState.rescaleError(100.);
  
   LogDebug("TransientInitialStateEstimator")
       << "the initial state is found to be:\n:" << firstState
       << "\n it's field pointer is: " << firstState.magneticField()
       << "\n the pointer from the state of the back fit was: " << firstMeas.updatedState().magneticField();
  
   return std::pair<TrajectoryStateOnSurface, const GeomDet*>(std::move(firstState), firstMeas.recHit()->det());
 }

References alongMomentum, Chi2MeasurementEstimator_cfi::Chi2MeasurementEstimator, Trajectory::direction(), Trajectory::firstMeasurement(), TrajectoryMeasurement::forwardPredictedState(), mps_fire::i, TrajectoryStateOnSurface::isValid(), Trajectory::isValid(), Trajectory::lastMeasurement(), TrajectoryStateOnSurface::localError(), TrajectoryStateOnSurface::localParameters(), LogDebug, TrajectoryFitter::looper, TrajectoryStateOnSurface::magneticField(), Propagator::magneticField(), Trajectory::measurements(), eostools::move(), Trajectory::nLoops(), oppositeToMomentum, rpcPointValidation_cfi::recHit, TrajectoryMeasurement::recHit(), TrajectoryStateOnSurface::rescaleError(), TrajectoryFitter::standard, TrajectoryStateOnSurface::surface(), theHitCloner, theNumberMeasurementsForFit, thePropagatorAlong, and TrajectoryMeasurement::updatedState().

◆ setEventSetup()

void TransientInitialStateEstimator::setEventSetup	(	const edm::EventSetup &	es,
		const TkClonerImpl &	hc
	)

Definition at line 28 of file TransientInitialStateEstimator.cc.

                                                                                                   {
   theHitCloner = hc;
  
   edm::ESHandle<Propagator> halong;
   edm::ESHandle<Propagator> hopposite;
  
   es.get<TrackingComponentsRecord>().get(thePropagatorAlongName, halong);
   es.get<TrackingComponentsRecord>().get(thePropagatorOppositeName, hopposite);
   thePropagatorAlong = halong.product();
   thePropagatorOpposite = hopposite.product();
 }