tracking::reco::DigitizationProcessor Class Reference

Digitization processor for the silicon strip tracker. More...

#include <DigitizationProcessor.h>

Public Member Functions
	DigitizationProcessor (const std::string &name, framework::Process &process)
void	onProcessStart () override
	Callback for the EventProcessor to take any necessary action when the processing of events starts, such as creating histograms.
void	configure (framework::config::Parameters &parameters) override
	Callback for the EventProcessor to configure itself from the given set of parameters.
void	onNewRun (const ldmx::RunHeader &header) override
	Before the run starts (but after the conditions are configured) set up the random seeds for this run.
void	produce (framework::Event &event) override
	Process the event and put new data products into it.
std::vector< ldmx::Measurement >	digitizeHits (const std::vector< ldmx::SimTrackerHit > &sim_hits, std::vector< ldmx::SimSiStripHit > *raw_hits=nullptr)
	Digitize a collection of SimTrackerHits into Measurements.
bool	mergeSimHits (const std::vector< ldmx::SimTrackerHit > &sim_hits, std::vector< ldmx::SimTrackerHit > &merged_hits)
bool	mergeHits (const std::vector< ldmx::SimTrackerHit > &sihits, std::vector< ldmx::SimTrackerHit > &mergedHits)
Public Member Functions inherited from tracking::reco::TrackingGeometryUser
	TrackingGeometryUser (const std::string &name, framework::Process &p)
Public Member Functions inherited from framework::Producer
	Producer (const std::string &name, Process &process)
	Class constructor.
virtual void	process (Event &event) final
	Processing an event for a Producer is calling produce.
Public Member Functions inherited from framework::EventProcessor
	DECLARE_FACTORY (EventProcessor, EventProcessor *, const std::string &, Process &)
	declare that we have a factory for this class
	EventProcessor (const std::string &name, Process &process)
	Class constructor.
virtual	~EventProcessor ()=default
	Class destructor.
virtual void	beforeNewRun (ldmx::RunHeader &run_header)
	Callback for Producers to add parameters to the run header before conditions are initialized.
virtual void	onFileOpen (EventFile &event_file)
	Callback for the EventProcessor to take any necessary action when a new event input ROOT file is opened.
virtual void	onFileClose (EventFile &event_file)
	Callback for the EventProcessor to take any necessary action when a event input ROOT file is closed.
virtual void	onProcessEnd ()
	Callback for the EventProcessor to take any necessary action when the processing of events finishes, such as calculating job-summary quantities.
template<class T >
const T &	getCondition (const std::string &condition_name)
	Access a conditions object for the current event.
TDirectory *	getHistoDirectory ()
	Access/create a directory in the histogram file for this event processor to create histograms and analysis tuples.
void	setStorageHint (framework::StorageControl::Hint hint)
	Mark the current event as having the given storage control hint from this module_.
void	setStorageHint (framework::StorageControl::Hint hint, const std::string &purposeString)
	Mark the current event as having the given storage control hint from this module and the given purpose string.
int	getLogFrequency () const
	Get the current logging frequency from the process.
int	getRunNumber () const
	Get the run number from the process.
std::string	getName () const
	Get the processor name.
void	createHistograms (const std::vector< framework::config::Parameters > &histos)
	Internal function which is used to create histograms passed from the python configuration @parma histos vector of Parameters that configure histograms to create.

Private Member Functions
void	buildLorentzCache ()

Private Attributes
std::string	hit_collection_
	Input hit collection to digitize.
std::string	out_collection_
	Output measurement collection name.
double	min_e_dep_
	Minimum energy deposition cut [MeV].
int	track_id_
	Select a particular track ID (-1 = accept all).
bool	merge_hits_ {false}
	Merge sim hits on the same sensor before digitizing.
bool	do_smearing_ {true}
	Flag to enable/disable smearing in Mode 0.
double	sigma_u_ {0}
	u-direction smearing sigma [mm].
double	sigma_v_ {0}
	v-direction smearing sigma [mm].
bool	use_charge_digitization_ {false}
	If true, use the full SiStripDigitizer instead of simple smearing.
tracking::digitization::SiStripDigitizer::SensorParams	sensor_params_
	Parameters forwarded to SiStripDigitizer.
std::unique_ptr< tracking::digitization::SiStripDigitizer >	strip_digitizer_
	The charge digitizer (constructed in onProcessStart).
std::string	out_raw_collection_ {""}
	Output raw hit collection name (empty = don't save raw hits).
std::unique_ptr< tracking::digitization::PulseShape >	pulse_shape_
	The constructed pulse shape (created in onProcessStart).
bool	use_lorentz_ {true}
	If false, skip Lorentz angle calculation and drift carriers straight (equivalent to zero magnetic field perpendicular to the sensor normal).
std::string	field_map_ {""}
	Path to the magnetic field map file.
std::unordered_map< unsigned int, std::pair< double, double > >	lorentz_tan_cache_
	Per-layer cached Lorentz tangents: layer_id → {tan_electron, tan_hole}.
std::string	tracker_hit_passname_
	Input collection pass name.
std::string	dump_geo_csv_ {""}
	If non-empty, write a CSV of all ACTS surface transforms to this path.
std::default_random_engine	generator_
std::shared_ptr< std::normal_distribution< float > >	normal_

Additional Inherited Members
Protected Member Functions inherited from tracking::reco::TrackingGeometryUser
const Acts::GeometryContext &	geometryContext ()
const Acts::MagneticFieldContext &	magneticFieldContext ()
const Acts::CalibrationContext &	calibrationContext ()
const geo::TrackersTrackingGeometry &	geometry ()
void	loadBField (const std::string &path, const BFieldDistortion &distortion={})
	Load the interpolated B-field map from path and cache it.
void	loadBField (const BFieldDistortion &distortion={})
	Load B-field from the path recorded in the detector GDML.
std::shared_ptr< Acts::MagneticFieldProvider >	bField () const
	Return the loaded B-field provider.
Protected Member Functions inherited from framework::EventProcessor
void	abortEvent ()
	Abort the event immediately.
Static Protected Member Functions inherited from tracking::reco::TrackingGeometryUser
static BFieldDistortion	bFieldDistortion (const framework::config::Parameters &parameters)
	Build a BFieldDistortion from processor configuration.
Protected Attributes inherited from framework::EventProcessor
HistogramPool	histograms_
	helper object for making and filling histograms
NtupleManager &	ntuple_ {NtupleManager::getInstance()}
	Manager for any ntuples.
logging::logger	the_log_
	The logger for this EventProcessor.

Detailed Description

Digitization processor for the silicon strip tracker.

Two modes are available, selected by the use_charge_digitization parameter:

Mode 0 (default, use_charge_digitization = false): Simple Gaussian smearing of the local coordinates. Fast and sufficient for most studies. Resolution set by sigma_u / sigma_v.

Mode 1 (use_charge_digitization = true): Realistic charge digitization. The track segment through the sensor is divided into sub-segments; each creates electron-hole pairs (N = Edep / E_pair). Thermal diffusion during drift spreads the charge as a Gaussian across strips. Electronic noise is added and a threshold is applied; the surviving strip cluster is clustered by a charge-weighted centroid to produce the local U measurement.

Definition at line 42 of file DigitizationProcessor.h.

Constructor & Destructor Documentation

DigitizationProcessor()

tracking::reco::DigitizationProcessor::DigitizationProcessor	(	const std::string &	name,
		framework::Process &	process )

Definition at line 18 of file DigitizationProcessor.cxx.

    : TrackingGeometryUser(name, process) {}

Member Function Documentation

buildLorentzCache()

void tracking::reco::DigitizationProcessor::buildLorentzCache ( )

private

Definition at line 144 of file DigitizationProcessor.cxx.

                                              {
  if (!use_charge_digitization_) return;
 
  if (field_map_.empty())
    loadBField();
  else
    loadBField(field_map_);
 
  // Low-field (Hall) mobility from the Canali model [cm²/(V·s)] → [m²/(V·s)]
  const double t = sensor_params_.temperature;
  auto carrier_e = tracking::digitization::getCarrier(-1);
  auto carrier_h = tracking::digitization::getCarrier(1);
  const double mu_e = carrier_e.mu0(t) * 1.0e-4;  // m²/(V·s)
  const double mu_h = carrier_h.mu0(t) * 1.0e-4;
 
  auto bfield_cache = bField()->makeCache(magneticFieldContext());
 
  for (const auto& [layer_id, surface] : geometry().layer_surface_map_) {
    const Acts::Vector3 center_mm = surface->center(geometryContext());
    const auto b_result = bField()->getField(center_mm, bfield_cache);
    if (!b_result.ok()) continue;
 
    // B in Tesla (ACTS field providers return values in Acts internal units)
    const Acts::Vector3 b_t = b_result.value() / Acts::UnitConstants::T;
 
    // Sensor W-normal = 3rd column of the rotation matrix
    const Acts::Vector3 w_hat =
        surface->localToGlobalTransform(geometryContext()).rotation().col(2);
 
    const double bw = b_t.dot(w_hat);  // [T]
 
    // tan(θ_L) = charge_sign · μ · Bw
    // electrons: charge = −1, holes: charge = +1
    const double tan_e = -mu_e * bw;
    const double tan_h = +mu_h * bw;
 
    lorentz_tan_cache_[layer_id] = {tan_e, tan_h};
 
    ldmx_log(debug) << "Lorentz cache: layer=" << layer_id << "  Bw=" << bw
                    << " T" << "  tan_e=" << tan_e << "  tan_h=" << tan_h;
  }
 
  ldmx_log(info) << "Lorentz tangents computed for "
                 << lorentz_tan_cache_.size() << " layers from field map "
                 << (field_map_.empty() ? geometry().fieldMapFile()
                                        : field_map_);
}

configure()

void tracking::reco::DigitizationProcessor::configure ( framework::config::Parameters & parameters )

overridevirtual

Callback for the EventProcessor to configure itself from the given set of parameters.

The parameters a processor has access to are the member variables of the python class in the sequence that has class_name equal to the EventProcessor class name.

For an example, look at MyProcessor.

Parameters

parameters

Parameters for configuration.

Reimplemented from framework::EventProcessor.

Definition at line 92 of file DigitizationProcessor.cxx.

                                           {
  hit_collection_ =
      parameters.get<std::string>("hit_collection", "TaggerSimHits");
 
  tracker_hit_passname_ = parameters.get<std::string>("tracker_hit_passname");
  out_collection_ =
      parameters.get<std::string>("out_collection", "OutputMeasuements");
  min_e_dep_ = parameters.get<double>("min_e_dep", 0.05);
  track_id_ = parameters.get<int>("track_id", -1);
  do_smearing_ = parameters.get<bool>("do_smearing", true);
  sigma_u_ = parameters.get<double>("sigma_u", 0.01);
  sigma_v_ = parameters.get<double>("sigma_v", 0.);
  merge_hits_ = parameters.get<bool>("merge_hits", false);
 
  // Mode 1: charge digitization parameters
  use_charge_digitization_ =
      parameters.get<bool>("use_charge_digitization", false);
 
  if (use_charge_digitization_) {
    sensor_params_.bias_voltage = parameters.get<double>("bias_voltage", 200.0);
    sensor_params_.depletion_voltage =
        parameters.get<double>("depletion_voltage", 70.0);
    sensor_params_.temperature = parameters.get<double>("temperature", 300.0);
    sensor_params_.noise_electrons =
        parameters.get<double>("noise_electrons", 1000.0);
    sensor_params_.threshold_electrons =
        parameters.get<double>("threshold_electrons", 3000.0);
    // Fixed sensor properties — not user-configurable.
    // LDMX (and HPS) use n-type bulk with hole-side readout.
    sensor_params_.is_n_type = true;
    sensor_params_.electron_side_readout = false;
    sensor_params_.hole_side_readout = true;
    use_lorentz_ = parameters.get<bool>("use_lorentz", true);
    sensor_params_.electron_lorentz_tangent =
        parameters.get<double>("electron_lorentz_tangent", 0.0);
    sensor_params_.hole_lorentz_tangent =
        parameters.get<double>("hole_lorentz_tangent", 0.0);
    sensor_params_.trapping = parameters.get<double>("trapping", 0.0);
    sensor_params_.deposition_granularity =
        parameters.get<double>("deposition_granularity", 0.10);
    sensor_params_.n_segments_min = parameters.get<int>("n_segments_min", 5);
    // n_readout_strips is fixed by the sensor geometry constant
    // N_READOUT_STRIPS.
 
    out_raw_collection_ = parameters.get<std::string>("out_raw_collection", "");
    field_map_ = parameters.get<std::string>("field_map", "");
  }
 
  dump_geo_csv_ = parameters.get<std::string>("dump_geo_csv", "");
}

References framework::config::Parameters::get().

digitizeHits()

std::vector< ldmx::Measurement > tracking::reco::DigitizationProcessor::digitizeHits	(	const std::vector< ldmx::SimTrackerHit > &	sim_hits,
		std::vector< ldmx::SimSiStripHit > *	raw_hits = nullptr )

Digitize a collection of SimTrackerHits into Measurements.

Operates in either smearing mode or full charge-digitization mode depending on the use_charge_digitization configuration flag.

Parameters

sim_hits	The collection of SimTrackerHits to digitize.
raw_hits	If non-null and charge digitization is active, filled with one SimSiStripHit per above-threshold readout strip.

Definition at line 330 of file DigitizationProcessor.cxx.

                                            {
  ldmx_log(debug) << "Found: " << sim_hits.size() << " sim hits in '"
                  << hit_collection_ << "' with passname '"
                  << tracker_hit_passname_ << "'";
 
  std::vector<ldmx::Measurement> measurements;
 
  struct StripContrib {
    double charge_electrons_;
    double hit_time_ns_;
    int track_id_;
    int pdg_id_;
    int sim_hit_id_;
    float edep_;
  };
  // layer_id -> strip_idx -> per-hit contributions (populated in Phase 1,
  // consumed in Phase 2 after the loop to apply noise once per strip)
  std::map<int, std::map<int, std::vector<StripContrib>>> layer_strip_contribs;
 
  for (auto& sim_hit : sim_hits) {
    // Energy deposition cut
    if (sim_hit.getEdep() <= min_e_dep_) continue;
    if (track_id_ > 0 && sim_hit.getTrackID() != track_id_) continue;
 
    ldmx::Measurement measurement(sim_hit);
 
    // Sensor identification
    auto layer_id = tracking::sim::utils::getSensorID(sim_hit);
    measurement.setLayerID(layer_id);
 
    auto hit_surface{geometry().getSurface(layer_id)};
    if (!hit_surface) continue;
 
    ldmx_log(trace)
        << "Local to global\n"
        << hit_surface->localToGlobalTransform(geometryContext()).rotation()
        << "\n"
        << hit_surface->localToGlobalTransform(geometryContext()).translation();
 
    // -----------------------------------------------------------------------
    // Project global hit position onto the surface (2D local coords)
    // -----------------------------------------------------------------------
    Acts::Vector3 dummy_momentum;
    Acts::Vector2 local_pos_2d;
 
    // TODO: clarify / derive the 0.320 mm surface tolerance from the geometry
    constexpr double surface_thickness = 0.320 * Acts::UnitConstants::mm;
 
    Acts::Vector3 global_pos(measurement.getGlobalPosition()[0],
                             measurement.getGlobalPosition()[1],
                             measurement.getGlobalPosition()[2]);
 
    try {
      local_pos_2d = hit_surface
                         ->globalToLocal(geometryContext(), global_pos,
                                         dummy_momentum, surface_thickness)
                         .value();
    } catch (const std::exception& e) {
      ldmx_log(warn) << "hit not on surface... Skipping.";
      continue;
    }
 
    // Store the projected truth U before any smearing or charge digitization.
    measurement.setTruthU(static_cast<float>(local_pos_2d[0]));
 
    // -----------------------------------------------------------------------
    // Mode 1: realistic charge digitization
    // -----------------------------------------------------------------------
    if (use_charge_digitization_) {
      // Read sensor thickness from the geometry.
      const auto* placement = hit_surface->surfacePlacement();
      if (!placement) {
        ldmx_log(warn) << "No detector element for layer_id=" << layer_id
                       << " — skipping hit";
        continue;
      }
      const double thickness =
          static_cast<const tracking::geo::DetectorElement*>(placement)
              ->thickness();
      strip_digitizer_->setThickness(thickness);
 
      // Build the full 3D local position and direction for charge simulation.
      const Acts::Transform3 surf_transform =
          hit_surface->localToGlobalTransform(geometryContext());
 
      // 3D local position: apply the inverse surface transform to the global
      // hit position so that we know the depth (W) coordinate.
      const Acts::Vector3 local_pos_3d = surf_transform.inverse() * global_pos;
 
      // 3D local direction: rotate the global unit momentum into local frame.
      // Apply the same LDMX→ACTS frame permutation as Measurement.cxx:
      //   ACTS-X = LDMX-z [2], ACTS-Y = LDMX-x [0], ACTS-Z = LDMX-y [1].
      Acts::Vector3 global_mom(sim_hit.getMomentum()[2],
                               sim_hit.getMomentum()[0],
                               sim_hit.getMomentum()[1]);
      const double mom_mag = global_mom.norm();
 
      Acts::Vector3 local_dir_3d;
      if (mom_mag > 0.0) {
        local_dir_3d =
            surf_transform.rotation().transpose() * (global_mom / mom_mag);
      } else {
        // Degenerate case: treat as normal incidence
        local_dir_3d = Acts::Vector3(0.0, 0.0, 1.0);
      }
 
      // Path length through the sensor; fall back to thickness / |cos θ|
      // if the stored value is not set.
      double path_length = sim_hit.getPathLength();
      if (path_length <= 0.0) {
        const double cos_theta = std::abs(local_dir_3d[2]);
        path_length = (cos_theta > 1e-3) ? thickness / cos_theta : thickness;
      }
 
      // Apply per-layer Lorentz tangents from the B-field cache (if available).
      if (use_lorentz_) {
        auto lorentz_it = lorentz_tan_cache_.find(layer_id);
        if (lorentz_it != lorentz_tan_cache_.end()) {
          strip_digitizer_->mutableParams().electron_lorentz_tangent =
              lorentz_it->second.first;
          strip_digitizer_->mutableParams().hole_lorentz_tangent =
              lorentz_it->second.second;
        }
      }
 
      // Compute charge deposited on each strip
      auto strip_charges = strip_digitizer_->computeStripCharges(
          sim_hit.getEdep(), local_pos_3d, local_dir_3d, path_length);
 
      ldmx_log(trace) << "Charge digi: " << strip_charges.size()
                      << " strips from computeStripCharges (pre-noise)";
 
      // Phase 1: accumulate this hit's strip charges into the per-layer map.
      // Noise is applied once per strip in Phase 2 (after the sim-hit loop)
      // so that overlapping contributions from different SimParticles are
      // summed before threshold is applied.
      if (raw_hits && pulse_shape_) {
        const double hit_time_ns = sim_hit.getTime();
        for (const auto& [strip_idx, charge] : strip_charges) {
          layer_strip_contribs[layer_id][strip_idx].push_back(StripContrib{
              charge, hit_time_ns, sim_hit.getTrackID(), sim_hit.getPdgID(),
              sim_hit.getID(), sim_hit.getEdep()});
        }
      }
 
      // Measurements are produced downstream by StripFitProcessor +
      // StripClusterProcessor for the reconstructed position, but we still
      // emit a truth-position Measurement here so that DigiDQM can build a
      // per-layer truth-U lookup for the sim_cluster_du residual.
      // Global position, time, edep, ID, and track ID are already populated
      // by the Measurement(sim_hit) constructor above; set local coords and
      // zero the covariance (this is a truth hit, not a smeared measurement).
      measurement.setLocalPosition(local_pos_2d(0), local_pos_2d(1));
      measurement.setLocalCovariance(0., 0.);
      measurements.push_back(measurement);
 
      // -----------------------------------------------------------------------
      // Mode 0: simple Gaussian smearing
      // -----------------------------------------------------------------------
    } else {
      if (do_smearing_) {
        float smear_factor{(*normal_)(generator_)};
        local_pos_2d[0] += smear_factor * sigma_u_;
        smear_factor = (*normal_)(generator_);
        local_pos_2d[1] += smear_factor * sigma_v_;
 
        measurement.setLocalCovariance(
            static_cast<float>(sigma_u_ * sigma_u_),
            static_cast<float>(tracking::digitization::SIGMA_V_MM *
                               tracking::digitization::SIGMA_V_MM));
 
        auto transf_global_pos{hit_surface->localToGlobal(
            geometryContext(), local_pos_2d, dummy_momentum)};
        measurement.setGlobalPosition(measurement.getGlobalPosition()[0],
                                      transf_global_pos(1),
                                      transf_global_pos(2));
      }
 
      measurement.setLocalPosition(local_pos_2d(0), local_pos_2d(1));
      measurements.push_back(measurement);
    }
  }  // loop over sim hits
 
  // Phase 2: apply noise once per strip across all sim-hit contributions,
  // then build SimSiStripHits with correctly superimposed pulse shapes.
  if (raw_hits && pulse_shape_) {
    const int adc_max = (1 << tracking::digitization::ADC_BITS) - 1;
 
    for (auto& [lyr_id, strip_contribs_map] : layer_strip_contribs) {
      // Sum all contributions to get the total pre-noise charge per strip.
      std::map<int, double> total_charges;
      for (const auto& [strip_idx, contribs] : strip_contribs_map) {
        double total = 0.0;
        for (const auto& c : contribs) total += c.charge_electrons_;
        total_charges[strip_idx] = total;
      }
 
      // Add noise to every strip (and its ±1 neighbours) then apply threshold.
      strip_digitizer_->applyNoiseAndThreshold(total_charges);
      if (total_charges.empty()) continue;
 
      for (const auto& [strip_idx, final_charge] : total_charges) {
        const auto contrib_it = strip_contribs_map.find(strip_idx);
        const bool has_signal = (contrib_it != strip_contribs_map.end());
 
        int track_id_out = -1;
        int pdg_id_out = 0;
        int sim_hit_id_out = -1;
        float edep_out = 0.f;
        double ref_time_ns = 0.0;
        std::vector<short> samples(tracking::digitization::N_SAMPLES);
 
        if (has_signal) {
          const auto& contribs = contrib_it->second;
 
          // Dominant contributor = strip's largest single charge deposit.
          const StripContrib* dom = &contribs.front();
          for (const auto& c : contribs)
            if (c.charge_electrons_ > dom->charge_electrons_) dom = &c;
 
          ref_time_ns = dom->hit_time_ns_;
          track_id_out = dom->track_id_;
          pdg_id_out = dom->pdg_id_;
          sim_hit_id_out = dom->sim_hit_id_;
          for (const auto& c : contribs) edep_out += c.edep_;
 
          // ADC = pedestal + superposition of each contributor's shaped pulse.
          for (int isamp = 0; isamp < tracking::digitization::N_SAMPLES;
               ++isamp) {
            const double t_samp =
                tracking::digitization::T0_OFFSET_NS +
                isamp * tracking::digitization::SAMPLING_INTERVAL_NS;
            double val =
                static_cast<double>(tracking::digitization::ADC_PEDESTAL);
            for (const auto& c : contribs)
              val += (c.charge_electrons_ /
                      tracking::digitization::ADC_ELECTRONS_PER_COUNT) *
                     pulse_shape_->eval(t_samp - c.hit_time_ns_);
            samples[isamp] = static_cast<short>(
                std::clamp(static_cast<int>(std::round(val)), 0, adc_max));
          }
        } else {
          // Noise-only strip: added as a ±1 neighbour by
          // applyNoiseAndThreshold. Borrow the nearest signal strip's dominant
          // hit time for pulse shaping.
          for (int delta : {-1, +1}) {
            const auto nb = strip_contribs_map.find(strip_idx + delta);
            if (nb != strip_contribs_map.end() && !nb->second.empty()) {
              const StripContrib* dom = &nb->second.front();
              for (const auto& c : nb->second)
                if (c.charge_electrons_ > dom->charge_electrons_) dom = &c;
              ref_time_ns = dom->hit_time_ns_;
              break;
            }
          }
          const double peak_adc =
              final_charge / tracking::digitization::ADC_ELECTRONS_PER_COUNT;
          for (int isamp = 0; isamp < tracking::digitization::N_SAMPLES;
               ++isamp) {
            const double t_samp =
                tracking::digitization::T0_OFFSET_NS +
                isamp * tracking::digitization::SAMPLING_INTERVAL_NS;
            const double val =
                static_cast<double>(tracking::digitization::ADC_PEDESTAL) +
                peak_adc * pulse_shape_->eval(t_samp - ref_time_ns);
            samples[isamp] = static_cast<short>(
                std::clamp(static_cast<int>(std::round(val)), 0, adc_max));
          }
        }
 
        raw_hits->emplace_back(lyr_id, strip_idx, std::move(samples),
                               static_cast<long>(ref_time_ns), track_id_out,
                               pdg_id_out, sim_hit_id_out, edep_out);
      }
    }
  }  // Phase 2
 
  return measurements;
}  // digitizeHits

References ldmx::Measurement::getGlobalPosition(), ldmx::Measurement::setGlobalPosition(), ldmx::Measurement::setLayerID(), ldmx::Measurement::setLocalCovariance(), ldmx::Measurement::setLocalPosition(), and ldmx::Measurement::setTruthU().

mergeHits()

bool tracking::reco::DigitizationProcessor::mergeHits	(	const std::vector< ldmx::SimTrackerHit > &	sihits,
		std::vector< ldmx::SimTrackerHit > &	mergedHits )

Definition at line 231 of file DigitizationProcessor.cxx.

                                              {
  if (sihits.size() < 1) return false;
 
  if (sihits.size() == 1) {
    mergedHits.push_back(sihits[0]);
    return true;
  }
 
  ldmx::SimTrackerHit merged_hit;
  merged_hit.setLayerID(sihits[0].getLayerID());
  merged_hit.setModuleID(sihits[0].getModuleID());
  merged_hit.setID(sihits[0].getID());
  merged_hit.setTrackID(sihits[0].getTrackID());
 
  double x{0}, y{0}, z{0}, px{0}, py{0}, pz{0};
  double t{0}, e{0}, edep{0}, path{0};
  int pdg_id = sihits[0].getPdgID();
 
  for (auto hit : sihits) {
    double edep_hit = hit.getEdep();
    edep += edep_hit;
    e += hit.getEnergy();
    t += edep_hit * hit.getTime();
    x += edep_hit * hit.getPosition()[0];
    y += edep_hit * hit.getPosition()[1];
    z += edep_hit * hit.getPosition()[2];
    px += edep_hit * hit.getMomentum()[0];
    py += edep_hit * hit.getMomentum()[1];
    pz += edep_hit * hit.getMomentum()[2];
    path += edep_hit * hit.getPathLength();
 
    if (hit.getPdgID() != pdg_id) {
      ldmx_log(error)
          << "ERROR:: Found hits with compatible sensorID and track_id "
             "but different PDGID";
      ldmx_log(error) << "TRACKID ==" << hit.getTrackID() << " vs "
                      << sihits[0].getTrackID();
      ldmx_log(error) << "PDGID== " << hit.getPdgID() << " vs " << pdg_id;
      return false;
    }
  }
 
  merged_hit.setTime(t / edep);
  merged_hit.setPosition(x / edep, y / edep, z / edep);
  merged_hit.setMomentum(px / edep, py / edep, pz / edep);
  merged_hit.setPathLength(path / edep);
  merged_hit.setEnergy(e);
  merged_hit.setEdep(edep);
  merged_hit.setPdgID(pdg_id);
 
  mergedHits.push_back(merged_hit);
  return true;
}

mergeSimHits()

bool tracking::reco::DigitizationProcessor::mergeSimHits	(	const std::vector< ldmx::SimTrackerHit > &	sim_hits,
		std::vector< ldmx::SimTrackerHit > &	merged_hits )

Definition at line 287 of file DigitizationProcessor.cxx.

                                               {
  // Key: [sensor_id][track_id] → list of hits to merge
  std::map<int, std::map<int, std::vector<ldmx::SimTrackerHit>>> hitmap;
 
  for (const auto& hit : sim_hits) {
    unsigned int index = tracking::sim::utils::getSensorID(hit);
    unsigned int trackid = hit.getTrackID();
    hitmap[index][trackid].push_back(hit);
 
    ldmx_log(trace) << "hitmap being filled, size::[" << index << "]["
                    << trackid << "] size " << hitmap[index][trackid].size();
  }
 
  typedef std::map<int,
                   std::map<int, std::vector<ldmx::SimTrackerHit>>>::iterator
      hitmap_it1;
  typedef std::map<int, std::vector<ldmx::SimTrackerHit>>::iterator hitmap_it2;
 
  for (hitmap_it1 it = hitmap.begin(); it != hitmap.end(); it++) {
    for (hitmap_it2 it2 = it->second.begin(); it2 != it->second.end(); it2++) {
      mergeHits(it2->second, merged_hits);
    }
  }
 
  ldmx_log(debug) << "Sim_hits Size = " << sim_hits.size()
                  << " Merged_hits Size = " << merged_hits.size();
 
  for (const auto& hit : sim_hits) {
    ldmx_log(trace) << hit;
  }
  for (const auto& mhit : merged_hits) {
    ldmx_log(trace) << mhit;
  }
 
  return true;
}

onNewRun()

void tracking::reco::DigitizationProcessor::onNewRun ( const ldmx::RunHeader & header )

overridevirtual

Before the run starts (but after the conditions are configured) set up the random seeds for this run.

Parameters

[in]

header

RunHeader for this run, unused

Reimplemented from framework::EventProcessor.

Definition at line 192 of file DigitizationProcessor.cxx.

                                                                   {
  const auto& rseed = getCondition<framework::RandomNumberSeedService>(
      framework::RandomNumberSeedService::CONDITIONS_OBJECT_NAME);
  const uint64_t seed = rseed.getSeed("Tracking::DigitizationProcessor");
  generator_.seed(seed);
  if (strip_digitizer_) strip_digitizer_->seed(seed);
}

References framework::RandomNumberSeedService::CONDITIONS_OBJECT_NAME.

onProcessStart()

void tracking::reco::DigitizationProcessor::onProcessStart ( )

overridevirtual

Callback for the EventProcessor to take any necessary action when the processing of events starts, such as creating histograms.

Reimplemented from framework::EventProcessor.

Definition at line 22 of file DigitizationProcessor.cxx.

                                           {
  normal_ = std::make_shared<std::normal_distribution<float>>(0., 1.);
 
  if (use_charge_digitization_) {
    strip_digitizer_ =
        std::make_unique<tracking::digitization::SiStripDigitizer>(
            sensor_params_);
    ldmx_log(info) << "Charge digitization enabled."
                   << "  thickness=from geometry"
                   << "  sense_pitch=" << tracking::digitization::SENSE_PITCH_MM
                   << " mm" << "  readout_pitch="
                   << tracking::digitization::READOUT_PITCH_MM << " mm"
                   << "  Vbias=" << sensor_params_.bias_voltage << " V"
                   << "  Vdep=" << sensor_params_.depletion_voltage << " V"
                   << "  bulk=" << (sensor_params_.is_n_type ? "n" : "p")
                   << "-type" << "  e_lorentz_tan="
                   << sensor_params_.electron_lorentz_tangent
                   << "  h_lorentz_tan=" << sensor_params_.hole_lorentz_tangent
                   << "  trapping=" << sensor_params_.trapping
                   << "  noise=" << sensor_params_.noise_electrons << " e-"
                   << "  threshold=" << sensor_params_.threshold_electrons
                   << " e-"
                   << "  n_segments_min=" << sensor_params_.n_segments_min
                   << "  granularity=" << sensor_params_.deposition_granularity;
 
    pulse_shape_ = tracking::digitization::PulseShape::make(
        std::string(tracking::digitization::PULSE_SHAPE_NAME),
        tracking::digitization::PEAKING_TIME_NS,
        tracking::digitization::SECOND_TIME_CONST_NS);
    ldmx_log(info) << "Pulse shaping: shape="
                   << tracking::digitization::PULSE_SHAPE_NAME
                   << "  tp=" << tracking::digitization::PEAKING_TIME_NS
                   << " ns"
                   << "  n_samples=" << tracking::digitization::N_SAMPLES
                   << "  sampling_interval="
                   << tracking::digitization::SAMPLING_INTERVAL_NS << " ns"
                   << "  t0_offset=" << tracking::digitization::T0_OFFSET_NS
                   << " ns";
 
    if (field_map_.empty()) {
      ldmx_log(debug) << "field_map not set; will auto-load from GDML";
    }
    if (use_lorentz_)
      buildLorentzCache();
    else
      ldmx_log(info)
          << "Lorentz angle correction disabled (use_lorentz=false).";
  }
 
  // Dump all ACTS surfaces to CSV for geometry verification.
  if (!dump_geo_csv_.empty()) {
    std::ofstream csv(dump_geo_csv_);
    csv << "layer_id,cx,cy,cz,Ux,Uy,Uz,Vx,Vy,Vz,Wx,Wy,Wz\n";
    for (const auto& [layer_id, surface] : geometry().layer_surface_map_) {
      const auto& xf = surface->localToGlobalTransform(geometryContext());
      const auto ctr = xf.translation();  // centre [mm in Acts units]
      const auto r = xf.rotation();
      const auto u = r.col(0);
      const auto v = r.col(1);
      const auto w = r.col(2);
      csv << layer_id << "," << ctr.x() << "," << ctr.y() << "," << ctr.z()
          << "," << u.x() << "," << u.y() << "," << u.z() << "," << v.x() << ","
          << v.y() << "," << v.z() << "," << w.x() << "," << w.y() << ","
          << w.z() << "\n";
    }
    ldmx_log(info) << "Surface geometry written to " << dump_geo_csv_ << "  ("
                   << geometry().layer_surface_map_.size() << " surfaces)";
  }
}

References tracking::digitization::PulseShape::make().

produce()

void tracking::reco::DigitizationProcessor::produce ( framework::Event & event )

overridevirtual

Process the event and put new data products into it.

Parameters

event

The Event to process.

Implements framework::Producer.

Definition at line 200 of file DigitizationProcessor.cxx.

                                                         {
  ldmx_log(trace) << " Getting the tracking geometry:" << geometry().getTG();
 
  const auto& sim_hits = event.getCollection<ldmx::SimTrackerHit>(
      hit_collection_, tracker_hit_passname_);
 
  std::vector<ldmx::SimTrackerHit> merged_hits;
  std::vector<ldmx::Measurement> measurements;
  std::vector<ldmx::SimSiStripHit> raw_hits;
 
  const bool save_raw =
      use_charge_digitization_ && !out_raw_collection_.empty();
  auto* raw_ptr = save_raw ? &raw_hits : nullptr;
 
  if (merge_hits_) {
    mergeSimHits(sim_hits, merged_hits);
    measurements = digitizeHits(merged_hits, raw_ptr);
  } else {
    measurements = digitizeHits(sim_hits, raw_ptr);
  }
 
  event.add(out_collection_, measurements);
  if (save_raw) {
    event.add(out_raw_collection_, raw_hits);
  }
}

Member Data Documentation

do_smearing_

bool tracking::reco::DigitizationProcessor::do_smearing_ {true}

private

Flag to enable/disable smearing in Mode 0.

Definition at line 98 of file DigitizationProcessor.h.

{true};

dump_geo_csv_

std::string tracking::reco::DigitizationProcessor::dump_geo_csv_ {""}

private

If non-empty, write a CSV of all ACTS surface transforms to this path.

Definition at line 142 of file DigitizationProcessor.h.

{""};

field_map_

std::string tracking::reco::DigitizationProcessor::field_map_ {""}

private

Path to the magnetic field map file.

Empty = use fixed configured tangents.

Definition at line 128 of file DigitizationProcessor.h.

{""};

generator_

std::default_random_engine tracking::reco::DigitizationProcessor::generator_

private

Definition at line 144 of file DigitizationProcessor.h.

hit_collection_

std::string tracking::reco::DigitizationProcessor::hit_collection_

private

Input hit collection to digitize.

Definition at line 83 of file DigitizationProcessor.h.

lorentz_tan_cache_

std::unordered_map<unsigned int, std::pair<double, double> > tracking::reco::DigitizationProcessor::lorentz_tan_cache_

private

Per-layer cached Lorentz tangents: layer_id → {tan_electron, tan_hole}.

Definition at line 131 of file DigitizationProcessor.h.

merge_hits_

bool tracking::reco::DigitizationProcessor::merge_hits_ {false}

private

Merge sim hits on the same sensor before digitizing.

Definition at line 92 of file DigitizationProcessor.h.

{false};

min_e_dep_

double tracking::reco::DigitizationProcessor::min_e_dep_

private

Minimum energy deposition cut [MeV].

Definition at line 88 of file DigitizationProcessor.h.

normal_

std::shared_ptr<std::normal_distribution<float> > tracking::reco::DigitizationProcessor::normal_

private

Definition at line 145 of file DigitizationProcessor.h.

out_collection_

std::string tracking::reco::DigitizationProcessor::out_collection_

private

Output measurement collection name.

Definition at line 85 of file DigitizationProcessor.h.

out_raw_collection_

std::string tracking::reco::DigitizationProcessor::out_raw_collection_ {""}

private

Output raw hit collection name (empty = don't save raw hits).

Definition at line 116 of file DigitizationProcessor.h.

{""};

pulse_shape_

std::unique_ptr<tracking::digitization::PulseShape> tracking::reco::DigitizationProcessor::pulse_shape_

private

The constructed pulse shape (created in onProcessStart).

Definition at line 118 of file DigitizationProcessor.h.

sensor_params_

tracking::digitization::SiStripDigitizer::SensorParams tracking::reco::DigitizationProcessor::sensor_params_

private

Parameters forwarded to SiStripDigitizer.

Definition at line 110 of file DigitizationProcessor.h.

sigma_u_

double tracking::reco::DigitizationProcessor::sigma_u_ {0}

private

u-direction smearing sigma [mm].

Definition at line 100 of file DigitizationProcessor.h.

{0};

sigma_v_

double tracking::reco::DigitizationProcessor::sigma_v_ {0}

private

v-direction smearing sigma [mm].

Definition at line 102 of file DigitizationProcessor.h.

{0};

strip_digitizer_

std::unique_ptr<tracking::digitization::SiStripDigitizer> tracking::reco::DigitizationProcessor::strip_digitizer_

private

The charge digitizer (constructed in onProcessStart).

Definition at line 112 of file DigitizationProcessor.h.

track_id_

int tracking::reco::DigitizationProcessor::track_id_

private

Select a particular track ID (-1 = accept all).

Definition at line 90 of file DigitizationProcessor.h.

tracker_hit_passname_

std::string tracking::reco::DigitizationProcessor::tracker_hit_passname_

private

Input collection pass name.

Definition at line 139 of file DigitizationProcessor.h.

use_charge_digitization_

bool tracking::reco::DigitizationProcessor::use_charge_digitization_ {false}

private

If true, use the full SiStripDigitizer instead of simple smearing.

Definition at line 108 of file DigitizationProcessor.h.

{false};

use_lorentz_

bool tracking::reco::DigitizationProcessor::use_lorentz_ {true}

private

If false, skip Lorentz angle calculation and drift carriers straight (equivalent to zero magnetic field perpendicular to the sensor normal).

Definition at line 125 of file DigitizationProcessor.h.

{true};

---

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

• Tracking/include/Tracking/Reco/DigitizationProcessor.h
• Tracking/src/Tracking/Reco/DigitizationProcessor.cxx