SensitiveDetector< SimHitClass, TrueHitClass > Class Template Reference

Sensitive Detector implementation of PXD and SVD. More...

#include <SensitiveDetector.h>

Inheritance diagram for SensitiveDetector< SimHitClass, TrueHitClass >:

Collaboration diagram for SensitiveDetector< SimHitClass, TrueHitClass >:

Public Member Functions
	SensitiveDetector (VXD::SensorInfoBase *sensorInfo)
	Construct instance and take over ownership of the sensorInfo pointer.
void	setOptions (bool seeNeutrons, bool onlyPrimaryTrueHits, float distanceTolerance, float electronTolerance, float minimumElectrons)
	Set all common options. More...
SensorInfoBase *	getSensorInfo ()
	Return a pointer to the SensorInfo associated with this instance.
VxdID	getSensorID () const
	Return the VxdID belonging to this sensitive detector.

Static Public Member Functions
static const std::map< std::string, RelationArray::EConsolidationAction > &	getMCParticleRelations ()
	Return a list of all registered Relations with MCParticles.
static void	setActive (bool activeStatus)
	Enable/Disable all Sensitive Detectors. More...
static void	registerMCParticleRelation (const std::string &name, RelationArray::EConsolidationAction ignoreAction=RelationArray::c_negativeWeight)
	Register an relation involving MCParticles. More...
static void	registerMCParticleRelation (const RelationArray &relation, RelationArray::EConsolidationAction ignoreAction=RelationArray::c_negativeWeight)
	Overload to make it easer to register MCParticle relations. More...

Protected Member Functions
std::vector< unsigned int >	simplifyEnergyDeposit (const SensorTraversal::range &points)
	Simplify the energy deposition profile using Douglas-Peuker-Algorithm We normally force a Geant4 step after 5µm but energy deposition does not necessarily vary much between these short steps. More...
StepInformation	findMidPoint (const SensorTraversal &traversal)
	Find the mid-point of the track traversal. More...

Private Member Functions
int	saveTrueHit (const SensorTraversal &traversal) override
	Save the actual TrueHit for a given sensor traversal information. More...
int	saveSimHit (const SensorTraversal &traversal, const SensorTraversal::range &points) override
	Save a SimHit for a track along the given points. More...
void	saveRelations (const SensorTraversal &traversal, int trueHitIndex, std::vector< std::pair< unsigned int, float >> simHitIndices) override
	Save the relations between MCParticle, TrueHit and SimHits. More...
std::array< float, 3 >	vecToFloat (const G4ThreeVector &vec)
	Convert G4ThreeVector (aka Hep3Vector) to float array to store in TrueHit/SimHit classes. More...
bool	step (G4Step *step, G4TouchableHistory *) override
	Process a single Geant4 Step. More...
bool	finishTrack ()
	Process a track once all steps are known. More...
std::vector< std::pair< unsigned int, float > >	createSimHits ()
	Determine which SimHits to create. More...
virtual bool	ProcessHits (G4Step *aStep, G4TouchableHistory *aROhist)
	Check if recording hits is enabled and if so call step() and set the correct MCParticle flag. More...

Private Attributes
StoreArray< SimHitClass >	m_simhits
	StoreArray for the SimHits.
StoreArray< TrueHitClass >	m_truehits
	StoreArray for the TrueHits.
StoreArray< MCParticle >	m_mcparticles
	StoreArray for the MCParticles, needed by relations.
RelationArray	m_relMCSimHits {m_mcparticles, m_simhits}
	Relation between MCParticle and SimHits.
RelationArray	m_relMCTrueHits {m_mcparticles, m_truehits}
	Relation between MCParticle and TrueHits.
RelationArray	m_relTrueSimHits {m_truehits, m_simhits}
	Relation between TrueHits and SimHits.
SensorInfoBase *	m_info {0}
	Pointer to the SensorInfo associated with this instance.
std::stack< SensorTraversal >	m_tracks
	stack of SensorTraversal information for all tracks not finished so far
float	m_distanceTolerance {0}
	maximum distance between step point and linear interpolation of sensor traversal before a new simhit object is created
float	m_electronTolerance {0}
	maximum relative difference between electron density of two steps where they can be considered similar enough to be merged
float	m_minimumElectrons {0}
	minimum number of electrons a track must deposit for SimHit/TrueHits to be created
bool	m_seeNeutrons {false}
	also create SimHit/TrueHit objects for neutrons (or charged particles which deposit less than m_minimumElectrons electrons
bool	m_onlyPrimaryTrueHits {false}
	only create TrueHits for primary particles
Const::EDetector	m_subdetector
	Subdetector the class belongs to.

Static Private Attributes
static std::map< std::string, RelationArray::EConsolidationAction >	s_mcRelations
	Static set holding all relations which have to be updated at the end of the Event.
static bool	s_active
	Static bool which indicates wether recording of hits is enabled.

Detailed Description

template<class SimHitClass, class TrueHitClass>
class Belle2::VXD::SensitiveDetector< SimHitClass, TrueHitClass >

Sensitive Detector implementation of PXD and SVD.

This class provides the actual implementation of the hit generation for PXD and SVD. It is templated to be able to create the corresponding output collection.

It generates two different kinds of Hits:

• SimHits which correspond to Geant4 steps inside the sensitive volume. There will be several SimHits per traversal, since the step length of Geant4 is limited to provide detailed information about energy deposition.
• TrueHits are aggregated objects which store the position where a particle crossed the detector plane (local z=0). There can be only one TrueHit per traversal of one sensor, but there may be more than one TrueHit for curling Tracks. TrueHits also carry information about the particle momenta before and after entering the silicon (or at start/end point if the track started/ended inside the silicon. MODIFIED July 2013 (based largely on suggestions by Martin Ritter):
  1. Every particle that either enters or leaves the sensitive volume and deposits some energy there, will create a TrueHit.
  2. The (u,v,w) position of the TrueHit are the coordinates of the midpoint of the track inside the sensitive volume (rather of the x-ing point with z=0): the w (z) coordinate is added to TrueHits.
  3. Each MC particle entering the sensitive volume will be un-ignored, so that the TrueHits created by secondaries entering the sensitive volume will be attributed to the correct MCParticle (that is, not to its primary ancestor).
  4. SimHit relations to MCParticles that don't produce a TrueHit and get re-attributed (to their primary ancestor) will have negative sign. This concerns the secondaries created inside the sensitive volume that don't reach another sensitive volume.

Template Parameters

SimHitClass	Class to use when generating SimHits
TrueHitClass	Class to use when generating TrueHits

Definition at line 67 of file SensitiveDetector.h.

Member Function Documentation

createSimHits()

std::vector< std::pair< unsigned int, float > > createSimHits ( )

privateinherited

Determine which SimHits to create.

A SimHit is a linear approximation of the particle trajectory. As such we try to combine as many Geant4 steps as possible by defining a distance tolerance and using the Douglas-Peucker algortihm to determine the required number of SimHits to keep the maximum distance of all Geant4 steps below that tolerance.

Returns

indices and electrons of all created simhits

Definition at line 133 of file SensitiveDetectorBase.cc.

                             {
        //Get first and last point
        std::tie(firstPoint, finalPoint) = stack.top();
        //Remove segment from stack
        stack.pop();
        //Direction of the segment
        const G4ThreeVector n = (finalPoint->position - firstPoint->position).unit();
        //find largest distance to segment by looping over all intermediate points
        double maxDistance(0);
        for (auto nextPoint = firstPoint + 1; nextPoint != finalPoint; ++nextPoint) {
          //Calculate distances between point p and line segment,
          //x = a + t*n, where a is a point on the line and n is the unit vector
          //pointing in line direction. distance = ||(p-a) - ((p-a)*n)*n||
          const G4ThreeVector pa = nextPoint->position - firstPoint->position;
          const double dist = (pa - (pa * n) * n).mag();
          //Update splitpoint if distance is larger then previously known
          if (dist > maxDistance) {
            splitPoint = nextPoint;
            maxDistance = dist;
          }
        }
        //If we are above the tolerance we split the track
        if (maxDistance > m_distanceTolerance) {
          //If we split in this order, all created simhits will be in correct
          //order. That is not a requirement but a nice side effect.
          stack.push(make_pair(splitPoint, finalPoint));
          stack.push(make_pair(firstPoint, splitPoint));
          continue;
        }
        //Otherwise we create a SimHit
        //FIXME: check for m_minimumElectrons?
        int simHitIndex = saveSimHit(traversal, std::make_pair(firstPoint, finalPoint));
        simhits.push_back(std::make_pair(simHitIndex, finalPoint->electrons - firstPoint->electrons));
      }
      return simhits;
    }
 
    std::vector<unsigned int> SensitiveDetectorBase::simplifyEnergyDeposit(const SensorTraversal::range& points)
    {
      //At the end we want a list of points indication how many electrons where
      //deposited so far along the track, e.g. [(0.5,100), (1.0, 2000)] would
      //indicate that after half the step length 100 electrons were deposited
      //and at the end of the step we have 2000 electrons. To save some memory
      //we encode this information as unsigned int using ElectronDeposit later

findMidPoint()

StepInformation findMidPoint ( const SensorTraversal &  traversal )

protectedinherited

Find the mid-point of the track traversal.

This function will return the position and momentum at the center of the track traversal, using cubic spline interpolation between the actual geant4 steps. Center is defined as "half the flight length" in this case.

Parameters

traversal

information on the particle traversal to be used when finding the midpoint

Returns

position and momentum at the mid point

Definition at line 281 of file SensitiveDetectorBase.cc.

finishTrack()

bool finishTrack ( )

privateinherited

Process a track once all steps are known.

This function decides whether TrueHit/SimHits will be saved

Definition at line 102 of file SensitiveDetectorBase.cc.

ProcessHits()

bool ProcessHits ( G4Step *  aStep, G4TouchableHistory *  aROhist  )

inlineprivatevirtualinherited

Check if recording hits is enabled and if so call step() and set the correct MCParticle flag.

Called by Geant4 for each step inside the sensitive volumes attached

Definition at line 98 of file SensitiveDetectorBase.h.

registerMCParticleRelation() [1/2]

static void registerMCParticleRelation ( const RelationArray &  relation, RelationArray::EConsolidationAction  ignoreAction = RelationArray::c_negativeWeight  )

inlinestaticinherited

Overload to make it easer to register MCParticle relations.

Parameters

relation	RelationArray to register
ignoreAction

Definition at line 70 of file SensitiveDetectorBase.h.

registerMCParticleRelation() [2/2]

void registerMCParticleRelation ( const std::string &  name, RelationArray::EConsolidationAction  ignoreAction = RelationArray::c_negativeWeight  )

staticinherited

Register an relation involving MCParticles.

All Relations which point from an MCParticle to something have to be registered with addMCParticleRelation() because the index of the MCParticles might change at the end of the event. During simulation, the TrackID should be used as index of the MCParticle

Parameters

name	Name of the relation to register
ignoreAction

Definition at line 24 of file SensitiveDetectorBase.cc.

saveRelations()

void saveRelations ( const SensorTraversal &  traversal, int  trueHitIndex, std::vector< std::pair< unsigned int, float >>  simHitIndices  )

overrideprivatevirtual

Save the relations between MCParticle, TrueHit and SimHits.

Parameters

traversal	information on the particle traversal to be used when creating the Relations
trueHitIndex	index of the TrueHit, <0 if no TrueHit was created
simHitIndices	indices of the SimHits along with the number of electrons deposited in each SimHit

Implements SensitiveDetectorBase.

Definition at line 188 of file SensitiveDetector.h.

    {
      m_relMCSimHits.add(traversal.getTrackID(), simHitIndices.begin(), simHitIndices.end());
      //If there is no truehit there are obviously no relations ;)
      if (trueHitIndex >= 0) {
        m_relMCTrueHits.add(traversal.getTrackID(), trueHitIndex, traversal.getElectrons());
        m_relTrueSimHits.add(trueHitIndex, simHitIndices.begin(), simHitIndices.end());
      }
    }

saveSimHit()

int saveSimHit ( const SensorTraversal &  traversal, const SensorTraversal::range &  points  )

overrideprivatevirtual

Save a SimHit for a track along the given points.

Parameters

traversal	information on the particle traversal to be used when creating the SimHit
points	pair of iterators to the first and last step position to be used for the SimHit

Returns

the index of the created SimHit in its StoreArray

Implements SensitiveDetectorBase.

Definition at line 166 of file SensitiveDetector.h.

saveTrueHit()

int saveTrueHit ( const SensorTraversal &  traversal )

overrideprivatevirtual

Save the actual TrueHit for a given sensor traversal information.

Parameters

traversal

information on the particle traversal to be used when creating the TrueHit

Returns

the index of the created TrueHit in its StoreArray

Implements SensitiveDetectorBase.

Definition at line 140 of file SensitiveDetector.h.

setActive()

static void setActive ( bool  activeStatus )

inlinestaticinherited

Enable/Disable all Sensitive Detectors.

By default, all sensitive detectors won't create hits to make it possible to use the Geant4 Navigator for non-simulation purposes. Only during simulation the sensitive detectors will be enabled to record hits

Parameters

activeStatus

bool to indicate wether hits should be recorded

Definition at line 54 of file SensitiveDetectorBase.h.

setOptions()

void setOptions ( bool  seeNeutrons, bool  onlyPrimaryTrueHits, float  distanceTolerance, float  electronTolerance, float  minimumElectrons  )

inlineinherited

Set all common options.

Parameters

seeNeutrons	if true, simhits are also stored for neutrons
onlyPrimaryTrueHits	if true, truehits will only be created for primary particles
distanceTolerance	maximal distance of step position from linear approximation.
electronTolerance	maximum deviation of energy deposition from linear approximation in electrons
minimumElectrons	minimum number of electrons to be deposited before SimHits are created.

Definition at line 70 of file SensitiveDetectorBase.h.

      {
        if (m_info) delete m_info;
      }
 

simplifyEnergyDeposit()

std::vector< unsigned int > simplifyEnergyDeposit ( const SensorTraversal::range &  points )

protectedinherited

Simplify the energy deposition profile using Douglas-Peuker-Algorithm We normally force a Geant4 step after 5µm but energy deposition does not necessarily vary much between these short steps.

Saving all steps would be a waste of space so we define a tolerance (in electrons) and keep only the points needed so that no point is further away from the profile than this tolerance.

Parameters

points

pair of iterators to the first and last point of the energy deposition profile

Returns

list of encoded EnergyDeposit values representing the simplified energy deposition profile.

Definition at line 190 of file SensitiveDetectorBase.cc.

step()

bool step ( G4Step *  step, G4TouchableHistory *    )

overrideprivatevirtualinherited

Process a single Geant4 Step.

This function stores the necessary information to create the TrueHits and SimHits and will call finishTrack() if a track leaves the volume or is stopped inside the volume.

Implements SensitiveDetectorBase.

Definition at line 37 of file SensitiveDetectorBase.cc.

vecToFloat()

std::array<float, 3> vecToFloat ( const G4ThreeVector &  vec )

inlineprivate

Convert G4ThreeVector (aka Hep3Vector) to float array to store in TrueHit/SimHit classes.

Parameters

vec	vector to convert

Returns

array containing x,y,z as floats

Definition at line 105 of file SensitiveDetector.h.

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The documentation for this class was generated from the following file:

• vxd/simulation/include/SensitiveDetector.h