algorithms/tracking/TrackerHitReconstruction.cc

0001 // SPDX-License-Identifier: LGPL-3.0-or-later
0002 // Copyright (C) 2022 - 2025 Whitney Armstrong, Sylvester Joosten, Wouter Deconinck, Dmitry Romanov
0003
0004 #include "TrackerHitReconstruction.h"
0005
0006 #include <DD4hep/Objects.h>
0007 #include <Evaluator/DD4hepUnits.h>
0008 #include <Math/GenVector/Cartesian3D.h>
0009 #include <Math/GenVector/DisplacementVector3D.h>
0010 #include <algorithms/logger.h>
0011 #include <edm4eic/CovDiag3f.h>
0012 #include <edm4hep/Vector3f.h>
0013 #include <cstddef>
0014 #include <exception>
0015 #include <iterator>
0016 #include <vector>
0017
0018 namespace eicrecon {
0019
0020 namespace {
0021   inline double get_resolution(const double pixel_size) {
0022     constexpr const double sqrt_12 = 3.4641016151;
0023     return pixel_size / sqrt_12;
0024   }
0025   inline double get_variance(const double pixel_size) {
0026     const double res = get_resolution(pixel_size);
0027     return res * res;
0028   }
0029 } // namespace
0030
0031 void TrackerHitReconstruction::process(const Input& input, const Output& output) const {
0032   using dd4hep::mm;
0033
0034   const auto [raw_hits] = input;
0035   auto [rec_hits]       = output;
0036
0037   for (const auto& raw_hit : *raw_hits) {
0038
0039     auto id = raw_hit.getCellID();
0040
0041     // Get position and dimension
0042     dd4hep::Position pos;
0043     std::vector<double> dim;
0044     try {
0045       pos = m_converter->position(id);
0046       dim = m_converter->cellDimensions(id);
0047     } catch (const std::exception& e) {
0048       error("Failed to get position and dimension for cell ID {:x}: {}", id, e.what());
0049       continue; // Skip this hit and continue with the next one
0050     }
0051
0052     // >oO trace
0053     if (level() == algorithms::LogLevel::kTrace) {
0054       trace("position x={:.2f} y={:.2f} z={:.2f} [mm]: ", pos.x() / mm, pos.y() / mm, pos.z() / mm);
0055       trace("dimension size: {}", dim.size());
0056       for (std::size_t j = 0; j < std::size(dim); ++j) {
0057         trace(" - dimension {:<5} size: {:.2}", j, dim[j]);
0058       }
0059     }
0060
0061     // Note about variance:
0062     //    The variance is used to obtain a diagonal covariance matrix.
0063     //    Note that the covariance matrix is written in DD4hep surface coordinates,
0064     //    *NOT* global position coordinates. This implies that:
0065     //      - XY segmentation: xx -> sigma_x, yy-> sigma_y, zz -> 0, tt -> 0
0066     //      - XZ segmentation: xx -> sigma_x, yy-> sigma_z, zz -> 0, tt -> 0
0067     //      - XYZ segmentation: xx -> sigma_x, yy-> sigma_y, zz -> sigma_z, tt -> 0
0068     //    This is properly in line with how we get the local coordinates for the hit
0069     //    in the TrackerSourceLinker.
0070     auto rec_hit = rec_hits->create(
0071         raw_hit.getCellID(), // Raw DD4hep cell ID
0072         edm4hep::Vector3f{static_cast<float>(pos.x() / mm), static_cast<float>(pos.y() / mm),
0073                           static_cast<float>(pos.z() / mm)}, // mm
0074         edm4eic::CovDiag3f{get_variance(dim[0] / mm),
0075                            get_variance(dim[1] / mm), // variance (see note above)
0076                            std::size(dim) > 2 ? get_variance(dim[2] / mm) : 0.},
0077         static_cast<float>((double)(raw_hit.getTimeStamp()) / 1000.0), // ns
0078         m_cfg.timeResolution,                                          // in ns
0079         static_cast<float>(raw_hit.getCharge() / 1.0e6),               // Collected energy (GeV)
0080         0.0F);                                                         // Error on the energy
0081     rec_hit.setRawHit(raw_hit);
0082   }
0083 }
0084
0085 } // namespace eicrecon