algorithms/pid/IrtCherenkovParticleID.cc

0001 // Copyright 2023, Christopher Dilks, adapted from Alexander Kiselev's Juggler implementation `IRTAlgorithm`
0002 // Subject to the terms in the LICENSE file found in the top-level directory.
0003
0004 #include "IrtCherenkovParticleID.h"
0005
0006 #include <IRT/ChargedParticle.h>
0007 #include <IRT/CherenkovPID.h>
0008 #include <IRT/OpticalPhoton.h>
0009 #include <IRT/RadiatorHistory.h>
0010 #include <IRT/SinglePDF.h>
0011 #include <TString.h>
0012 #include <TVector3.h>
0013 #include <algorithms/logger.h>
0014 #include <edm4eic/CherenkovParticleIDHypothesis.h>
0015 #include <edm4eic/TrackPoint.h>
0016 #include <edm4hep/EDM4hepVersion.h>
0017 #include <edm4hep/MCParticleCollection.h>
0018 #include <edm4hep/SimTrackerHitCollection.h>
0019 #include <edm4hep/Vector2f.h>
0020 #include <edm4hep/Vector3d.h>
0021 #include <edm4hep/Vector3f.h>
0022 #include <fmt/core.h>
0023 #include <fmt/format.h>
0024 #include <podio/ObjectID.h>
0025 #include <podio/RelationRange.h>
0026 #include <algorithm>
0027 #include <cmath>
0028 #include <cstddef>
0029 #include <functional>
0030 #include <iterator>
0031 #include <memory>
0032 #include <set>
0033 #include <stdexcept>
0034 #include <utility>
0035 #include <vector>
0036
0037 #include "algorithms/pid/IrtCherenkovParticleIDConfig.h"
0038 #include "algorithms/pid/Tools.h"
0039
0040 namespace eicrecon {
0041
0042 void IrtCherenkovParticleID::init(CherenkovDetectorCollection* irt_det_coll) {
0043   // members
0044   m_irt_det_coll = irt_det_coll;
0045
0046   // print the configuration parameters
0047   debug() << m_cfg << endmsg;
0048
0049   // inform the user if a cheat mode is enabled
0050   auto print_cheat = [this](auto name, bool val, auto desc) {
0051     if (val) {
0052       warning("CHEAT MODE '{}' ENABLED: {}", name, desc);
0053     }
0054   };
0055   print_cheat("cheatPhotonVertex", m_cfg.cheatPhotonVertex,
0056               "use MC photon vertex, wavelength, refractive index");
0057   print_cheat("cheatTrueRadiator", m_cfg.cheatTrueRadiator, "use MC truth to obtain true radiator");
0058
0059   // extract the relevant `CherenkovDetector`, set to `m_irt_det`
0060   const auto& detectors = m_irt_det_coll->GetDetectors();
0061   if (detectors.empty()) {
0062     throw std::runtime_error("No CherenkovDetectors found in input collection `irt_det_coll`");
0063   }
0064   if (detectors.size() > 1) {
0065     warning("IrtCherenkovParticleID currently only supports 1 CherenkovDetector at a time; "
0066             "taking the first");
0067   }
0068   auto this_detector = *detectors.begin();
0069   m_det_name         = this_detector.first;
0070   m_irt_det          = this_detector.second;
0071   debug("Initializing IrtCherenkovParticleID algorithm for CherenkovDetector '{}'", m_det_name);
0072
0073   // readout decoding
0074   m_cell_mask = m_irt_det->GetReadoutCellMask();
0075   debug("readout cellMask = {:#X}", m_cell_mask);
0076
0077   // rebin refractive index tables to have `m_cfg.numRIndexBins` bins
0078   trace("Rebinning refractive index tables to have {} bins", m_cfg.numRIndexBins);
0079   for (auto [rad_name, irt_rad] : m_irt_det->Radiators()) {
0080     // FIXME: m_cfg.numRIndexBins should be a service configurable
0081     std::lock_guard<std::mutex> lock(m_irt_det_mutex);
0082     auto ri_lookup_table_orig = irt_rad->m_ri_lookup_table;
0083     if (ri_lookup_table_orig.size() != m_cfg.numRIndexBins) {
0084       irt_rad->m_ri_lookup_table.clear();
0085       irt_rad->m_ri_lookup_table =
0086           Tools::ApplyFineBinning(ri_lookup_table_orig, m_cfg.numRIndexBins);
0087     }
0088   }
0089
0090   // build `m_pid_radiators`, the list of radiators to use for PID
0091   debug("Obtain List of Radiators:");
0092   for (auto [rad_name, irt_rad] : m_irt_det->Radiators()) {
0093     if (rad_name != "Filter") {
0094       m_pid_radiators.insert({std::string(rad_name), irt_rad});
0095       debug("- {}", rad_name.Data());
0096     }
0097   }
0098
0099   // check radiators' configuration, and pass it to `m_irt_det`'s radiators
0100   for (auto [rad_name, irt_rad] : m_pid_radiators) {
0101     std::lock_guard<std::mutex> lock(m_irt_det_mutex);
0102     // find `cfg_rad`, the associated `IrtCherenkovParticleIDConfig` radiator
0103     auto cfg_rad_it = m_cfg.radiators.find(rad_name);
0104     if (cfg_rad_it != m_cfg.radiators.end()) {
0105       auto cfg_rad = cfg_rad_it->second;
0106       // pass `cfg_rad` params to `irt_rad`, the IRT radiator
0107       irt_rad->m_ID                     = Tools::GetRadiatorID(std::string(rad_name));
0108       irt_rad->m_AverageRefractiveIndex = cfg_rad.referenceRIndex;
0109       irt_rad->SetReferenceRefractiveIndex(cfg_rad.referenceRIndex);
0110       if (cfg_rad.attenuation > 0) {
0111         irt_rad->SetReferenceAttenuationLength(cfg_rad.attenuation);
0112       }
0113       if (cfg_rad.smearing > 0) {
0114         if (cfg_rad.smearingMode == "uniform") {
0115           irt_rad->SetUniformSmearing(cfg_rad.smearing);
0116         } else if (cfg_rad.smearingMode == "gaussian") {
0117           irt_rad->SetGaussianSmearing(cfg_rad.smearing);
0118         } else {
0119           error("Unknown smearing mode '{}' for {} radiator", cfg_rad.smearingMode, rad_name);
0120         }
0121       }
0122     } else {
0123       error("Cannot find radiator '{}' in IrtCherenkovParticleIDConfig instance", rad_name);
0124     }
0125   }
0126
0127   // get PDG info for the particles we want to identify in PID
0128   debug("List of particles for PID:");
0129   for (auto pdg : m_cfg.pdgList) {
0130     auto mass = m_particleSvc.particle(pdg).mass;
0131     m_pdg_mass.insert({pdg, mass});
0132     debug("  {:>8}  M={} GeV", pdg, mass);
0133   }
0134 }
0135
0136 void IrtCherenkovParticleID::process(const IrtCherenkovParticleID::Input& input,
0137                                      const IrtCherenkovParticleID::Output& output) const {
0138   const auto [in_aerogel_tracks, in_gas_tracks, in_merged_tracks, in_raw_hits, in_hit_assocs] =
0139       input;
0140   auto [out_aerogel_particleIDs, out_gas_particleIDs] = output;
0141
0142   // logging
0143   trace("{:=^70}", " call IrtCherenkovParticleID::AlgorithmProcess ");
0144   trace("number of raw sensor hits: {}", in_raw_hits->size());
0145   trace("number of raw sensor hit with associated photons: {}", in_hit_assocs->size());
0146
0147   std::map<std::string, const edm4eic::TrackSegmentCollection*> in_charged_particles{
0148       {"Aerogel", in_aerogel_tracks},
0149       {"Gas", in_gas_tracks},
0150       {"Merged", in_merged_tracks},
0151   };
0152
0153   // start output collections
0154   std::map<std::string, edm4eic::CherenkovParticleIDCollection*> out_cherenkov_pids{
0155       {"Aerogel", out_aerogel_particleIDs}, {"Gas", out_gas_particleIDs}};
0156
0157   // check `in_charged_particles`: each radiator should have the same number of TrackSegments
0158   std::unordered_map<std::size_t, std::size_t> in_charged_particle_size_distribution;
0159   for (const auto& [rad_name, in_charged_particle] : in_charged_particles) {
0160     ++in_charged_particle_size_distribution[in_charged_particle->size()];
0161   }
0162   if (in_charged_particle_size_distribution.size() != 1) {
0163     std::vector<std::size_t> in_charged_particle_sizes;
0164     std::ranges::transform(
0165         in_charged_particles, std::back_inserter(in_charged_particle_sizes),
0166         [](const auto& in_charged_particle) { return in_charged_particle.second->size(); });
0167     error("radiators have differing numbers of TrackSegments {}",
0168           fmt::join(in_charged_particle_sizes, ", "));
0169     return;
0170   }
0171
0172   // loop over charged particles ********************************************
0173   trace("{:#<70}", "### CHARGED PARTICLES ");
0174   std::size_t num_charged_particles = in_charged_particle_size_distribution.begin()->first;
0175   for (std::size_t i_charged_particle = 0; i_charged_particle < num_charged_particles;
0176        i_charged_particle++) {
0177     trace("{:-<70}", fmt::format("--- charged particle #{} ", i_charged_particle));
0178
0179     // start an `irt_particle`, for `IRT`
0180     auto irt_particle = std::make_unique<ChargedParticle>();
0181
0182     // loop over radiators
0183     // note: this must run exclusively since irt_rad points to shared IRT objects that are
0184     // owned by the RichGeo_service; it holds state (e.g. irt_rad->ResetLocation())
0185     std::lock_guard<std::mutex> lock(m_irt_det_mutex);
0186     for (auto [rad_name, irt_rad] : m_pid_radiators) {
0187
0188       // get the `charged_particle` for this radiator
0189       auto charged_particle_list_it = in_charged_particles.find(rad_name);
0190       if (charged_particle_list_it == in_charged_particles.end()) {
0191         error("Cannot find radiator '{}' in `in_charged_particles`", rad_name);
0192         continue;
0193       }
0194       const auto* charged_particle_list = charged_particle_list_it->second;
0195       auto charged_particle             = charged_particle_list->at(i_charged_particle);
0196
0197       // set number of bins for this radiator and charged particle
0198       if (charged_particle.points_size() == 0) {
0199         trace("No propagated track points in radiator '{}'", rad_name);
0200         continue;
0201       }
0202       irt_rad->SetTrajectoryBinCount(charged_particle.points_size() - 1);
0203
0204       // start a new IRT `RadiatorHistory`
0205       // - must be a raw pointer for `irt` compatibility
0206       // - it will be destroyed when `irt_particle` is destroyed
0207       auto* irt_rad_history = new RadiatorHistory();
0208       irt_particle->StartRadiatorHistory({irt_rad, irt_rad_history});
0209
0210       // loop over `TrackPoint`s of this `charged_particle`, adding each to the IRT radiator
0211       irt_rad->ResetLocations();
0212       trace("TrackPoints in '{}' radiator:", rad_name);
0213       for (const auto& point : charged_particle.getPoints()) {
0214         TVector3 position = Tools::PodioVector3_to_TVector3(point.position);
0215         TVector3 momentum = Tools::PodioVector3_to_TVector3(point.momentum);
0216         irt_rad->AddLocation(position, momentum);
0217         trace(Tools::PrintTVector3(" point: x", position));
0218         trace(Tools::PrintTVector3("        p", momentum));
0219       }
0220
0221       // loop over raw hits ***************************************************
0222       trace("{:#<70}", "### SENSOR HITS ");
0223       for (const auto& raw_hit : *in_raw_hits) {
0224
0225         // get MC photon(s), typically only used by cheat modes or trace logging
0226         // - loop over `in_hit_assocs`, searching for the matching hit association
0227         // - will not exist for noise hits
0228         edm4hep::MCParticle mc_photon;
0229         bool mc_photon_found = false;
0230         if (m_cfg.cheatPhotonVertex || m_cfg.cheatTrueRadiator) {
0231           for (const auto& hit_assoc : *in_hit_assocs) {
0232             if (hit_assoc.getRawHit().isAvailable()) {
0233               if (hit_assoc.getRawHit().id() == raw_hit.id()) {
0234 #if EDM4HEP_BUILD_VERSION >= EDM4HEP_VERSION(0, 99, 0)
0235                 mc_photon = hit_assoc.getSimHit().getParticle();
0236 #else
0237                 mc_photon = hit_assoc.getSimHit().getMCParticle();
0238 #endif
0239                 mc_photon_found = true;
0240                 if (mc_photon.getPDG() != -22) {
0241                   warning("non-opticalphoton hit: PDG = {}", mc_photon.getPDG());
0242                 }
0243                 break;
0244               }
0245             }
0246           }
0247         }
0248
0249         // cheat mode, for testing only: use MC photon to get the actual radiator
0250         if (m_cfg.cheatTrueRadiator && mc_photon_found) {
0251           auto vtx     = Tools::PodioVector3_to_TVector3(mc_photon.getVertex());
0252           auto* mc_rad = m_irt_det->GuessRadiator(vtx, vtx); // assume IP is at (0,0,0)
0253           if (mc_rad != irt_rad) {
0254             continue; // skip this photon, if not from radiator `irt_rad`
0255           }
0256           trace(Tools::PrintTVector3(
0257               fmt::format("cheat: radiator '{}' determined from photon vertex", rad_name), vtx));
0258         }
0259
0260         // get sensor and pixel info
0261         // FIXME: signal and timing cuts (ADC, TDC, ToT, ...)
0262         auto cell_id       = raw_hit.getCellID();
0263         uint64_t sensor_id = cell_id & m_cell_mask;
0264         TVector3 pixel_pos = m_irt_det->m_ReadoutIDToPosition(cell_id);
0265
0266         // trace logging
0267         if (level() <= algorithms::LogLevel::kTrace) {
0268           trace("cell_id={:#X}  sensor_id={:#X}", cell_id, sensor_id);
0269           trace(Tools::PrintTVector3("pixel position", pixel_pos));
0270           if (mc_photon_found) {
0271             TVector3 mc_endpoint = Tools::PodioVector3_to_TVector3(mc_photon.getEndpoint());
0272             trace(Tools::PrintTVector3("photon endpoint", mc_endpoint));
0273             trace("{:>30} = {}", "dist( pixel,  photon )", (pixel_pos - mc_endpoint).Mag());
0274           } else {
0275             trace("  no MC photon found; probably a noise hit");
0276           }
0277         }
0278
0279         // start new IRT photon
0280         auto* irt_sensor = m_irt_det->m_PhotonDetectors[0]; // NOTE: assumes one sensor type
0281         auto* irt_photon =
0282             new OpticalPhoton(); // new raw pointer; it will also be destroyed when `irt_particle` is destroyed
0283         irt_photon->SetVolumeCopy(sensor_id);
0284         irt_photon->SetDetectionPosition(pixel_pos);
0285         irt_photon->SetPhotonDetector(irt_sensor);
0286         irt_photon->SetDetected(true);
0287
0288         // cheat mode: get photon vertex info from MC truth
0289         if ((m_cfg.cheatPhotonVertex || m_cfg.cheatTrueRadiator) && mc_photon_found) {
0290           irt_photon->SetVertexPosition(Tools::PodioVector3_to_TVector3(mc_photon.getVertex()));
0291           irt_photon->SetVertexMomentum(Tools::PodioVector3_to_TVector3(mc_photon.getMomentum()));
0292         }
0293
0294         // cheat mode: retrieve a refractive index estimate; it is not exactly the one, which
0295         // was used in GEANT, but should be very close
0296         if (m_cfg.cheatPhotonVertex) {
0297           double ri   = NAN;
0298           auto mom    = 1e9 * irt_photon->GetVertexMomentum().Mag();
0299           auto ri_set = Tools::GetFinelyBinnedTableEntry(irt_rad->m_ri_lookup_table, mom, &ri);
0300           if (ri_set) {
0301             irt_photon->SetVertexRefractiveIndex(ri);
0302             trace("{:>30} = {}", "refractive index", ri);
0303           } else {
0304             warning("Tools::GetFinelyBinnedTableEntry failed to lookup refractive index for "
0305                     "momentum {} eV",
0306                     mom);
0307           }
0308         }
0309
0310         // add each `irt_photon` to the radiator history
0311         // - unless cheating, we don't know which photon goes with which
0312         // radiator, thus we add them all to each radiator; the radiators'
0313         // photons are mixed in `ChargedParticle::PIDReconstruction`
0314         irt_rad_history->AddOpticalPhoton(irt_photon);
0315         /* FIXME: this considers ALL of the `irt_photon`s... we can limit this
0316          * once we add the ability to get a fiducial volume for each track, i.e.,
0317          * a region of sensors where we expect to see this `irt_particle`'s
0318          * Cherenkov photons; this should also combat sensor noise
0319          */
0320       } // end `in_hit_assocs` loop
0321
0322     } // end radiator loop
0323
0324     // particle identification +++++++++++++++++++++++++++++++++++++++++++++++++++++
0325
0326     // define a mass hypothesis for each particle we want to check
0327     trace("{:+^70}", " PARTICLE IDENTIFICATION ");
0328     CherenkovPID irt_pid;
0329     std::unordered_map<int, MassHypothesis*> pdg_to_hyp; // `pdg` -> hypothesis
0330     for (auto [pdg, mass] : m_pdg_mass) {
0331       irt_pid.AddMassHypothesis(mass);
0332       pdg_to_hyp.insert({pdg, irt_pid.GetHypothesis(irt_pid.GetHypothesesCount() - 1)});
0333     }
0334
0335     // run IRT PID
0336     irt_particle->PIDReconstruction(irt_pid);
0337     trace("{:-^70}", " IRT RESULTS ");
0338
0339     // loop over radiators
0340     for (auto [rad_name, irt_rad] : m_pid_radiators) {
0341       trace("-> {} Radiator (ID={}):", rad_name, irt_rad->m_ID);
0342
0343       // Cherenkov angle (theta) estimate
0344       unsigned npe      = 0;
0345       double rindex_ave = 0.0;
0346       double energy_ave = 0.0;
0347       std::vector<std::pair<double, double>> phot_theta_phi;
0348
0349       // loop over this radiator's photons, and decide which to include in the theta estimate
0350       auto* irt_rad_history = irt_particle->FindRadiatorHistory(irt_rad);
0351       if (irt_rad_history == nullptr) {
0352         trace("  No radiator history; skip");
0353         continue;
0354       }
0355       trace("  Photoelectrons:");
0356       for (auto* irt_photon : irt_rad_history->Photons()) {
0357
0358         // check whether this photon was selected by at least one mass hypothesis
0359         bool photon_selected = false;
0360         for (auto irt_photon_sel : irt_photon->_m_Selected) {
0361           if (irt_photon_sel.second == irt_rad) {
0362             photon_selected = true;
0363             break;
0364           }
0365         }
0366         if (!photon_selected) {
0367           continue;
0368         }
0369
0370         // trace logging
0371         trace(
0372             Tools::PrintTVector3(fmt::format("- sensor_id={:#X}: hit", irt_photon->GetVolumeCopy()),
0373                                  irt_photon->GetDetectionPosition()));
0374         trace(Tools::PrintTVector3("photon vertex", irt_photon->GetVertexPosition()));
0375
0376         // get this photon's theta and phi estimates
0377         auto phot_theta = irt_photon->_m_PDF[irt_rad].GetAverage();
0378         auto phot_phi   = irt_photon->m_Phi[irt_rad];
0379
0380         // add to the total
0381         npe++;
0382         phot_theta_phi.emplace_back(phot_theta, phot_phi);
0383         if (m_cfg.cheatPhotonVertex) {
0384           rindex_ave += irt_photon->GetVertexRefractiveIndex();
0385           energy_ave += irt_photon->GetVertexMomentum().Mag();
0386         }
0387
0388       } // end loop over this radiator's photons
0389
0390       // compute averages
0391       if (npe > 0) {
0392         rindex_ave /= npe;
0393         energy_ave /= npe;
0394       }
0395
0396       // fill photon info
0397       auto out_cherenkov_pid = out_cherenkov_pids.at(rad_name)->create();
0398       out_cherenkov_pid.setNpe(static_cast<decltype(edm4eic::CherenkovParticleIDData::npe)>(npe));
0399       out_cherenkov_pid.setRefractiveIndex(
0400           static_cast<decltype(edm4eic::CherenkovParticleIDData::refractiveIndex)>(rindex_ave));
0401       out_cherenkov_pid.setPhotonEnergy(
0402           static_cast<decltype(edm4eic::CherenkovParticleIDData::photonEnergy)>(energy_ave));
0403       for (auto [phot_theta, phot_phi] : phot_theta_phi) {
0404         out_cherenkov_pid.addToThetaPhiPhotons(
0405             edm4hep::Vector2f{static_cast<float>(phot_theta), static_cast<float>(phot_phi)});
0406       }
0407
0408       // relate mass hypotheses
0409       for (auto [pdg, mass] : m_pdg_mass) {
0410
0411         // get hypothesis results
0412         auto* irt_hypothesis = pdg_to_hyp.at(pdg);
0413         auto hyp_weight      = irt_hypothesis->GetWeight(irt_rad);
0414         auto hyp_npe         = irt_hypothesis->GetNpe(irt_rad);
0415
0416         // fill `ParticleID` output collection
0417         edm4eic::CherenkovParticleIDHypothesis out_hypothesis;
0418         out_hypothesis.PDG =
0419             static_cast<decltype(edm4eic::CherenkovParticleIDHypothesis::PDG)>(pdg);
0420         out_hypothesis.weight =
0421             static_cast<decltype(edm4eic::CherenkovParticleIDHypothesis::weight)>(hyp_weight);
0422         out_hypothesis.npe =
0423             static_cast<decltype(edm4eic::CherenkovParticleIDHypothesis::npe)>(hyp_npe);
0424
0425         // relate
0426         out_cherenkov_pid.addToHypotheses(out_hypothesis);
0427
0428       } // end hypothesis loop
0429
0430       // logging: Cherenkov angle estimate
0431       auto PrintCherenkovEstimate = [this](edm4eic::CherenkovParticleID pid,
0432                                            bool printHypotheses = true, int indent = 2) {
0433         double thetaAve = 0;
0434         if (pid.getNpe() > 0) {
0435           for (const auto& [theta, phi] : pid.getThetaPhiPhotons()) {
0436             thetaAve += theta / pid.getNpe();
0437           }
0438         }
0439         trace("{:{}}Cherenkov Angle Estimate:", "", indent);
0440         trace("{:{}}  {:>16}:  {:>10}", "", indent, "NPE", pid.getNpe());
0441         trace("{:{}}  {:>16}:  {:>10.8} mrad", "", indent, "<theta>",
0442               thetaAve * 1e3); // [rad] -> [mrad]
0443         trace("{:{}}  {:>16}:  {:>10.8}", "", indent, "<rindex>", pid.getRefractiveIndex());
0444         trace("{:{}}  {:>16}:  {:>10.8} eV", "", indent, "<energy>",
0445               pid.getPhotonEnergy() * 1e9); // [GeV] -> [eV]
0446         if (printHypotheses) {
0447           trace("{:{}}Mass Hypotheses:", "", indent);
0448           trace("{}", Tools::HypothesisTableHead(indent + 2));
0449           for (const auto& hyp : pid.getHypotheses()) {
0450             trace("{}", Tools::HypothesisTableLine(hyp, indent + 2));
0451           }
0452         }
0453       };
0454       PrintCherenkovEstimate(out_cherenkov_pid);
0455
0456       // relate charged particle projection
0457       auto charged_particle_list_it = in_charged_particles.find("Merged");
0458       if (charged_particle_list_it != in_charged_particles.end()) {
0459         const auto* charged_particle_list = charged_particle_list_it->second;
0460         auto charged_particle             = charged_particle_list->at(i_charged_particle);
0461         out_cherenkov_pid.setChargedParticle(charged_particle);
0462       } else {
0463         error("Cannot find radiator 'Merged' in `in_charged_particles`");
0464       }
0465
0466       // relate hit associations
0467       for (const auto& hit_assoc : *in_hit_assocs) {
0468         out_cherenkov_pid.addToRawHitAssociations(hit_assoc);
0469       }
0470
0471     } // end radiator loop
0472
0473     /* NOTE: `unique_ptr irt_particle` goes out of scope and will now be destroyed, and along with it:
0474      * - raw pointer `irt_rad_history` for each radiator
0475      * - all `irt_photon` raw pointers
0476      */
0477
0478   } // end `in_charged_particles` loop
0479 }
0480
0481 } // namespace eicrecon