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