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 <fmt/core.h>
0021 #include <fmt/format.h>
0022 #include <cmath>
0023
0024 #include <algorithm>
0025 #include <cstddef>
0026 #include <functional>
0027 #include <gsl/pointers>
0028 #include <iterator>
0029 #include <memory>
0030 #include <podio/ObjectID.h>
0031 #include <podio/RelationRange.h>
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::transform(
0165         in_charged_particles.begin(), in_charged_particles.end(),
0166         std::back_inserter(in_charged_particle_sizes),
0167         [](const auto& in_charged_particle) { return in_charged_particle.second->size(); });
0168     error("radiators have differing numbers of TrackSegments {}",
0169           fmt::join(in_charged_particle_sizes, ", "));
0170     return;
0171   }
0172
0173   // loop over charged particles ********************************************
0174   trace("{:#<70}", "### CHARGED PARTICLES ");
0175   std::size_t num_charged_particles = in_charged_particle_size_distribution.begin()->first;
0176   for (std::size_t i_charged_particle = 0; i_charged_particle < num_charged_particles;
0177        i_charged_particle++) {
0178     trace("{:-<70}", fmt::format("--- charged particle #{} ", i_charged_particle));
0179
0180     // start an `irt_particle`, for `IRT`
0181     auto irt_particle = std::make_unique<ChargedParticle>();
0182
0183     // loop over radiators
0184     // note: this must run exclusively since irt_rad points to shared IRT objects that are
0185     // owned by the RichGeo_service; it holds state (e.g. irt_rad->ResetLocation())
0186     std::lock_guard<std::mutex> lock(m_irt_det_mutex);
0187     for (auto [rad_name, irt_rad] : m_pid_radiators) {
0188
0189       // get the `charged_particle` for this radiator
0190       auto charged_particle_list_it = in_charged_particles.find(rad_name);
0191       if (charged_particle_list_it == in_charged_particles.end()) {
0192         error("Cannot find radiator '{}' in `in_charged_particles`", rad_name);
0193         continue;
0194       }
0195       const auto* charged_particle_list = charged_particle_list_it->second;
0196       auto charged_particle             = charged_particle_list->at(i_charged_particle);
0197
0198       // set number of bins for this radiator and charged particle
0199       if (charged_particle.points_size() == 0) {
0200         trace("No propagated track points in radiator '{}'", rad_name);
0201         continue;
0202       }
0203       irt_rad->SetTrajectoryBinCount(charged_particle.points_size() - 1);
0204
0205       // start a new IRT `RadiatorHistory`
0206       // - must be a raw pointer for `irt` compatibility
0207       // - it will be destroyed when `irt_particle` is destroyed
0208       auto* irt_rad_history = new RadiatorHistory();
0209       irt_particle->StartRadiatorHistory({irt_rad, irt_rad_history});
0210
0211       // loop over `TrackPoint`s of this `charged_particle`, adding each to the IRT radiator
0212       irt_rad->ResetLocations();
0213       trace("TrackPoints in '{}' radiator:", rad_name);
0214       for (const auto& point : charged_particle.getPoints()) {
0215         TVector3 position = Tools::PodioVector3_to_TVector3(point.position);
0216         TVector3 momentum = Tools::PodioVector3_to_TVector3(point.momentum);
0217         irt_rad->AddLocation(position, momentum);
0218         trace(Tools::PrintTVector3(" point: x", position));
0219         trace(Tools::PrintTVector3("        p", momentum));
0220       }
0221
0222       // loop over raw hits ***************************************************
0223       trace("{:#<70}", "### SENSOR HITS ");
0224       for (const auto& raw_hit : *in_raw_hits) {
0225
0226         // get MC photon(s), typically only used by cheat modes or trace logging
0227         // - loop over `in_hit_assocs`, searching for the matching hit association
0228         // - will not exist for noise hits
0229         edm4hep::MCParticle mc_photon;
0230         bool mc_photon_found = false;
0231         if (m_cfg.cheatPhotonVertex || m_cfg.cheatTrueRadiator) {
0232           for (const auto& hit_assoc : *in_hit_assocs) {
0233             if (hit_assoc.getRawHit().isAvailable()) {
0234               if (hit_assoc.getRawHit().id() == raw_hit.id()) {
0235 #if EDM4HEP_BUILD_VERSION >= EDM4HEP_VERSION(0, 99, 0)
0236                 mc_photon = hit_assoc.getSimHit().getParticle();
0237 #else
0238                 mc_photon = hit_assoc.getSimHit().getMCParticle();
0239 #endif
0240                 mc_photon_found = true;
0241                 if (mc_photon.getPDG() != -22) {
0242                   warning("non-opticalphoton hit: PDG = {}", mc_photon.getPDG());
0243                 }
0244                 break;
0245               }
0246             }
0247           }
0248         }
0249
0250         // cheat mode, for testing only: use MC photon to get the actual radiator
0251         if (m_cfg.cheatTrueRadiator && mc_photon_found) {
0252           auto vtx     = Tools::PodioVector3_to_TVector3(mc_photon.getVertex());
0253           auto* mc_rad = m_irt_det->GuessRadiator(vtx, vtx); // assume IP is at (0,0,0)
0254           if (mc_rad != irt_rad) {
0255             continue; // skip this photon, if not from radiator `irt_rad`
0256           }
0257           trace(Tools::PrintTVector3(
0258               fmt::format("cheat: radiator '{}' determined from photon vertex", rad_name), vtx));
0259         }
0260
0261         // get sensor and pixel info
0262         // FIXME: signal and timing cuts (ADC, TDC, ToT, ...)
0263         auto cell_id       = raw_hit.getCellID();
0264         uint64_t sensor_id = cell_id & m_cell_mask;
0265         TVector3 pixel_pos = m_irt_det->m_ReadoutIDToPosition(cell_id);
0266
0267         // trace logging
0268         if (level() <= algorithms::LogLevel::kTrace) {
0269           trace("cell_id={:#X}  sensor_id={:#X}", cell_id, sensor_id);
0270           trace(Tools::PrintTVector3("pixel position", pixel_pos));
0271           if (mc_photon_found) {
0272             TVector3 mc_endpoint = Tools::PodioVector3_to_TVector3(mc_photon.getEndpoint());
0273             trace(Tools::PrintTVector3("photon endpoint", mc_endpoint));
0274             trace("{:>30} = {}", "dist( pixel,  photon )", (pixel_pos - mc_endpoint).Mag());
0275           } else {
0276             trace("  no MC photon found; probably a noise hit");
0277           }
0278         }
0279
0280         // start new IRT photon
0281         auto* irt_sensor = m_irt_det->m_PhotonDetectors[0]; // NOTE: assumes one sensor type
0282         auto* irt_photon =
0283             new OpticalPhoton(); // new raw pointer; it will also be destroyed when `irt_particle` is destroyed
0284         irt_photon->SetVolumeCopy(sensor_id);
0285         irt_photon->SetDetectionPosition(pixel_pos);
0286         irt_photon->SetPhotonDetector(irt_sensor);
0287         irt_photon->SetDetected(true);
0288
0289         // cheat mode: get photon vertex info from MC truth
0290         if ((m_cfg.cheatPhotonVertex || m_cfg.cheatTrueRadiator) && mc_photon_found) {
0291           irt_photon->SetVertexPosition(Tools::PodioVector3_to_TVector3(mc_photon.getVertex()));
0292           irt_photon->SetVertexMomentum(Tools::PodioVector3_to_TVector3(mc_photon.getMomentum()));
0293         }
0294
0295         // cheat mode: retrieve a refractive index estimate; it is not exactly the one, which
0296         // was used in GEANT, but should be very close
0297         if (m_cfg.cheatPhotonVertex) {
0298           double ri   = NAN;
0299           auto mom    = 1e9 * irt_photon->GetVertexMomentum().Mag();
0300           auto ri_set = Tools::GetFinelyBinnedTableEntry(irt_rad->m_ri_lookup_table, mom, &ri);
0301           if (ri_set) {
0302             irt_photon->SetVertexRefractiveIndex(ri);
0303             trace("{:>30} = {}", "refractive index", ri);
0304           } else {
0305             warning("Tools::GetFinelyBinnedTableEntry failed to lookup refractive index for "
0306                     "momentum {} eV",
0307                     mom);
0308           }
0309         }
0310
0311         // add each `irt_photon` to the radiator history
0312         // - unless cheating, we don't know which photon goes with which
0313         // radiator, thus we add them all to each radiator; the radiators'
0314         // photons are mixed in `ChargedParticle::PIDReconstruction`
0315         irt_rad_history->AddOpticalPhoton(irt_photon);
0316         /* FIXME: this considers ALL of the `irt_photon`s... we can limit this
0317          * once we add the ability to get a fiducial volume for each track, i.e.,
0318          * a region of sensors where we expect to see this `irt_particle`'s
0319          * Cherenkov photons; this should also combat sensor noise
0320          */
0321       } // end `in_hit_assocs` loop
0322
0323     } // end radiator loop
0324
0325     // particle identification +++++++++++++++++++++++++++++++++++++++++++++++++++++
0326
0327     // define a mass hypothesis for each particle we want to check
0328     trace("{:+^70}", " PARTICLE IDENTIFICATION ");
0329     CherenkovPID irt_pid;
0330     std::unordered_map<int, MassHypothesis*> pdg_to_hyp; // `pdg` -> hypothesis
0331     for (auto [pdg, mass] : m_pdg_mass) {
0332       irt_pid.AddMassHypothesis(mass);
0333       pdg_to_hyp.insert({pdg, irt_pid.GetHypothesis(irt_pid.GetHypothesesCount() - 1)});
0334     }
0335
0336     // run IRT PID
0337     irt_particle->PIDReconstruction(irt_pid);
0338     trace("{:-^70}", " IRT RESULTS ");
0339
0340     // loop over radiators
0341     for (auto [rad_name, irt_rad] : m_pid_radiators) {
0342       trace("-> {} Radiator (ID={}):", rad_name, irt_rad->m_ID);
0343
0344       // Cherenkov angle (theta) estimate
0345       unsigned npe      = 0;
0346       double rindex_ave = 0.0;
0347       double energy_ave = 0.0;
0348       std::vector<std::pair<double, double>> phot_theta_phi;
0349
0350       // loop over this radiator's photons, and decide which to include in the theta estimate
0351       auto* irt_rad_history = irt_particle->FindRadiatorHistory(irt_rad);
0352       if (irt_rad_history == nullptr) {
0353         trace("  No radiator history; skip");
0354         continue;
0355       }
0356       trace("  Photoelectrons:");
0357       for (auto* irt_photon : irt_rad_history->Photons()) {
0358
0359         // check whether this photon was selected by at least one mass hypothesis
0360         bool photon_selected = false;
0361         for (auto irt_photon_sel : irt_photon->_m_Selected) {
0362           if (irt_photon_sel.second == irt_rad) {
0363             photon_selected = true;
0364             break;
0365           }
0366         }
0367         if (!photon_selected) {
0368           continue;
0369         }
0370
0371         // trace logging
0372         trace(
0373             Tools::PrintTVector3(fmt::format("- sensor_id={:#X}: hit", irt_photon->GetVolumeCopy()),
0374                                  irt_photon->GetDetectionPosition()));
0375         trace(Tools::PrintTVector3("photon vertex", irt_photon->GetVertexPosition()));
0376
0377         // get this photon's theta and phi estimates
0378         auto phot_theta = irt_photon->_m_PDF[irt_rad].GetAverage();
0379         auto phot_phi   = irt_photon->m_Phi[irt_rad];
0380
0381         // add to the total
0382         npe++;
0383         phot_theta_phi.emplace_back(phot_theta, phot_phi);
0384         if (m_cfg.cheatPhotonVertex) {
0385           rindex_ave += irt_photon->GetVertexRefractiveIndex();
0386           energy_ave += irt_photon->GetVertexMomentum().Mag();
0387         }
0388
0389       } // end loop over this radiator's photons
0390
0391       // compute averages
0392       if (npe > 0) {
0393         rindex_ave /= npe;
0394         energy_ave /= npe;
0395       }
0396
0397       // fill photon info
0398       auto out_cherenkov_pid = out_cherenkov_pids.at(rad_name)->create();
0399       out_cherenkov_pid.setNpe(static_cast<decltype(edm4eic::CherenkovParticleIDData::npe)>(npe));
0400       out_cherenkov_pid.setRefractiveIndex(
0401           static_cast<decltype(edm4eic::CherenkovParticleIDData::refractiveIndex)>(rindex_ave));
0402       out_cherenkov_pid.setPhotonEnergy(
0403           static_cast<decltype(edm4eic::CherenkovParticleIDData::photonEnergy)>(energy_ave));
0404       for (auto [phot_theta, phot_phi] : phot_theta_phi) {
0405         out_cherenkov_pid.addToThetaPhiPhotons(
0406             edm4hep::Vector2f{static_cast<float>(phot_theta), static_cast<float>(phot_phi)});
0407       }
0408
0409       // relate mass hypotheses
0410       for (auto [pdg, mass] : m_pdg_mass) {
0411
0412         // get hypothesis results
0413         auto* irt_hypothesis = pdg_to_hyp.at(pdg);
0414         auto hyp_weight      = irt_hypothesis->GetWeight(irt_rad);
0415         auto hyp_npe         = irt_hypothesis->GetNpe(irt_rad);
0416
0417         // fill `ParticleID` output collection
0418         edm4eic::CherenkovParticleIDHypothesis out_hypothesis;
0419         out_hypothesis.PDG =
0420             static_cast<decltype(edm4eic::CherenkovParticleIDHypothesis::PDG)>(pdg);
0421         out_hypothesis.weight =
0422             static_cast<decltype(edm4eic::CherenkovParticleIDHypothesis::weight)>(hyp_weight);
0423         out_hypothesis.npe =
0424             static_cast<decltype(edm4eic::CherenkovParticleIDHypothesis::npe)>(hyp_npe);
0425
0426         // relate
0427         out_cherenkov_pid.addToHypotheses(out_hypothesis);
0428
0429       } // end hypothesis loop
0430
0431       // logging: Cherenkov angle estimate
0432       auto PrintCherenkovEstimate = [this](edm4eic::CherenkovParticleID pid,
0433                                            bool printHypotheses = true, int indent = 2) {
0434         double thetaAve = 0;
0435         if (pid.getNpe() > 0) {
0436           for (const auto& [theta, phi] : pid.getThetaPhiPhotons()) {
0437             thetaAve += theta / pid.getNpe();
0438           }
0439         }
0440         trace("{:{}}Cherenkov Angle Estimate:", "", indent);
0441         trace("{:{}}  {:>16}:  {:>10}", "", indent, "NPE", pid.getNpe());
0442         trace("{:{}}  {:>16}:  {:>10.8} mrad", "", indent, "<theta>",
0443               thetaAve * 1e3); // [rad] -> [mrad]
0444         trace("{:{}}  {:>16}:  {:>10.8}", "", indent, "<rindex>", pid.getRefractiveIndex());
0445         trace("{:{}}  {:>16}:  {:>10.8} eV", "", indent, "<energy>",
0446               pid.getPhotonEnergy() * 1e9); // [GeV] -> [eV]
0447         if (printHypotheses) {
0448           trace("{:{}}Mass Hypotheses:", "", indent);
0449           trace("{}", Tools::HypothesisTableHead(indent + 2));
0450           for (const auto& hyp : pid.getHypotheses()) {
0451             trace("{}", Tools::HypothesisTableLine(hyp, indent + 2));
0452           }
0453         }
0454       };
0455       PrintCherenkovEstimate(out_cherenkov_pid);
0456
0457       // relate charged particle projection
0458       auto charged_particle_list_it = in_charged_particles.find("Merged");
0459       if (charged_particle_list_it != in_charged_particles.end()) {
0460         const auto* charged_particle_list = charged_particle_list_it->second;
0461         auto charged_particle             = charged_particle_list->at(i_charged_particle);
0462         out_cherenkov_pid.setChargedParticle(charged_particle);
0463       } else {
0464         error("Cannot find radiator 'Merged' in `in_charged_particles`");
0465       }
0466
0467       // relate hit associations
0468       for (const auto& hit_assoc : *in_hit_assocs) {
0469         out_cherenkov_pid.addToRawHitAssociations(hit_assoc);
0470       }
0471
0472     } // end radiator loop
0473
0474     /* NOTE: `unique_ptr irt_particle` goes out of scope and will now be destroyed, and along with it:
0475      * - raw pointer `irt_rad_history` for each radiator
0476      * - all `irt_photon` raw pointers
0477      */
0478
0479   } // end `in_charged_particles` loop
0480 }
0481
0482 } // namespace eicrecon