gparticle.cc

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// gemc
#include "gutilities.h"
 
// gparticle
#include "gparticle.h"
#include "gparticleConventions.h"
 
// geant4
#include "G4ParticleTable.hh"
#include "Randomize.hh"
 
using std::ostream;
using std::string;
 
// Constructor based on parameters.
// Detailed API documentation is in gparticle.h.
Gparticle::Gparticle(const std::string&              aname,
                     int                             amultiplicity,
                     double                          ap,
                     double                          adelta_p,
                     const std::string&              arandomMomentumModel,
                     double                          atheta,
                     double                          adelta_theta,
                     const std::string&              arandomThetaModel,
                     double                          aphi,
                     double                          adelta_phi,
                     double                          avx,
                     double                          avy,
                     double                          avz,
                     double                          adelta_vx,
                     double                          adelta_vy,
                     double                          adelta_vz,
                     const std::string&              arandomVertexModel,
                     const std::shared_ptr<GLogger>& logger,
                     int                             agenerator_type) :
    name(aname),
    generator_type(agenerator_type),
    multiplicity(amultiplicity),
    p(ap),
    delta_p(adelta_p),
    randomMomentumModel(gutilities::stringToRandomModel(arandomMomentumModel)),
    theta(atheta),
    delta_theta(adelta_theta),
    randomThetaModel(gutilities::stringToRandomModel(arandomThetaModel)),
    phi(aphi),
    delta_phi(adelta_phi),
    v(G4ThreeVector(avx, avy, avz)),
    delta_v(G4ThreeVector(adelta_vx, adelta_vy, adelta_vz)),
    randomVertexModel(gutilities::stringToRandomModel(arandomVertexModel)),
    log(logger) {
    // Resolve PDG id immediately so errors are detected early and configuration printing is complete.
    pid = get_pdg_id();
 
    log->debug(CONSTRUCTOR, "Gparticle");
}
 
 
// Shoots this particle into the provided event using the provided Geant4 particle gun.
// Detailed API documentation is in gparticle.h.
std::vector<GparticleRuntimeRecord> Gparticle::shootParticle(G4ParticleGun* particleGun,
                                                             G4Event* anEvent) const {
    auto particleTable = G4ParticleTable::GetParticleTable();
    std::vector<GparticleRuntimeRecord> runtime_records;
    if (multiplicity > 0) { runtime_records.reserve(static_cast<size_t>(multiplicity)); }
 
    if (particleTable) {
        // Resolve the particle definition by name.
        auto particleDef = particleTable->FindParticle(name);
 
        if (particleDef) {
            // Mass is used to convert randomized momentum magnitude into kinetic energy.
            double mass = particleDef->GetPDGMass();
            particleGun->SetParticleDefinition(particleDef);
 
 
            // Shoot one primary vertex per multiplicity.
            for (int i = 0; i < multiplicity; i++) {
                auto pmev = calculateMomentum();
                auto kenergy = sqrt(pmev * pmev + mass * mass) - mass;
                auto thetaRad = randomizeNumberFromSigmaWithModel(theta, delta_theta, randomThetaModel) / CLHEP::rad;
                auto phiRad   = randomizeNumberFromSigmaWithModel(phi, delta_phi, gutilities::uniform) / CLHEP::rad;
                auto beamDirection = calculateBeamDirection(thetaRad, phiRad);
                auto vertex        = calculateVertex();
 
                runtime_records.push_back({
                    name,
                    pid,
                    generator_type,
                    pmev,
                    thetaRad * CLHEP::rad,
                    phiRad * CLHEP::rad,
                    vertex
                });
 
                particleGun->SetParticleEnergy(kenergy);
                particleGun->SetParticleMomentumDirection(beamDirection);
                particleGun->SetParticlePosition(vertex);
                particleGun->GeneratePrimaryVertex(anEvent);
 
                log->info(
                    2,
                    "Generated particle <%1> pid %2, p [MeV]: %3, theta [deg]: %4, phi [deg]: %5, vertex "
                    "[cm]: %6", name, pid, pmev / CLHEP::MeV, thetaRad / CLHEP::deg, phiRad / CLHEP::deg,
                    vertex / CLHEP::cm);
            }
        }
        else {
            log->error(
                gparticle::ERR_GPARTICLENOTFOUND, "Particle <%1> not found in G4ParticleTable* %2", name,
                particleTable);
        }
    }
    else {
        log->error(
            gparticle::ERR_GPARTICLETABLENOTFOUND, "G4ParticleTable not found - G4ParticleGun*: %1",
            particleGun);
    }
 
    return runtime_records;
}
 
 
double Gparticle::calculateMomentum() const {
    // randomizeNumberFromSigmaWithModel applies the model-dependent interpretation of delta.
    double pmev = randomizeNumberFromSigmaWithModel(p, delta_p, randomMomentumModel);
 
    return pmev;
}
 
double Gparticle::calculateKinEnergy(double mass) const {
    double pmev = calculateMomentum();
 
    return sqrt(pmev * pmev + mass * mass) - mass;
}
 
 
G4ThreeVector Gparticle::calculateBeamDirection(double thetaRad, double phiRad) const {
    G4ThreeVector pdir = G4ThreeVector(
                                       cos(phiRad) * sin(thetaRad),
                                       sin(phiRad) * sin(thetaRad),
                                       cos(thetaRad)
                                      );
 
    return pdir;
}
 
G4ThreeVector Gparticle::calculateVertex() const {
    double x, y, z;
 
    switch (randomVertexModel) {
        case gutilities::uniform:
            // Component-wise uniform sampling around the nominal vertex.
            x = randomizeNumberFromSigmaWithModel(v.x(), delta_v.x(), gutilities::uniform);
            y = randomizeNumberFromSigmaWithModel(v.y(), delta_v.y(), gutilities::uniform);
            z = randomizeNumberFromSigmaWithModel(v.z(), delta_v.z(), gutilities::uniform);
            break;
 
        case gutilities::gaussian:
            // Component-wise Gaussian sampling around the nominal vertex (deltas used as sigmas).
            x = randomizeNumberFromSigmaWithModel(v.x(), delta_v.x(), gutilities::gaussian);
            y = randomizeNumberFromSigmaWithModel(v.y(), delta_v.y(), gutilities::gaussian);
            z = randomizeNumberFromSigmaWithModel(v.z(), delta_v.z(), gutilities::gaussian);
            break;
 
        case gutilities::sphere: {
            // Sample an offset inside a sphere-like region whose maximum radius is delta_v.r().
            // Assumes all three components have comparable spread such that delta_v.r() is meaningful.
            double radius;
            double max_radius = delta_v.r();
 
            // Rejection sampling: generate a random point in a cube until it lies within the radius bound.
            do {
                x      = randomizeNumberFromSigmaWithModel(0, max_radius, gutilities::uniform);
                y      = randomizeNumberFromSigmaWithModel(0, max_radius, gutilities::uniform);
                z      = randomizeNumberFromSigmaWithModel(0, max_radius, gutilities::uniform);
                radius = x * x + y * y + z * z;
            }
            while (radius > max_radius * max_radius);
 
            // Offset the sampled point by the nominal vertex.
            x = x + v.x();
            y = y + v.y();
            z = z + v.z();
            break;
        }
 
        default:
            // Unknown model: fall back to deterministic vertex.
            x = v.x();
            y = v.y();
            z = v.z();
            break;
    }
 
    return {x, y, z};
}
 
 
double Gparticle::randomizeNumberFromSigmaWithModel(double center, double delta, gutilities::randomModel model) const {
    switch (model) {
        case gutilities::uniform:
            // Uniform in [center-delta, center+delta].
            return center + ( 2.0 * G4UniformRand() - 1.0 ) * delta;
 
        case gutilities::gaussian:
            // Gaussian with mean=center and sigma=delta.
            return G4RandGauss::shoot(center, delta);
 
        case gutilities::cosine: {
            // assuming this is an angle with corrected units
            // For cosine-weighted sampling we work in radians, sample theta with sin(theta) weighting,
            // and then enforce the requested [center-delta, center+delta] range.
            double lower      = ( center - delta ) / CLHEP::rad;
            double upper      = ( center + delta ) / CLHEP::rad;
            double center_rad = 0;
 
            if (lower < upper) {
                // Generate theta such that cos(theta) is uniform, which corresponds to sin(theta) weighting.
                do { center_rad = acos(1 - 2 * G4UniformRand()); }
                while (center_rad < lower || center_rad > upper);
            }
            else {
                // Degenerate range: fall back to the stored theta value.
                center_rad = theta / CLHEP::rad;
            }
 
            return center_rad * CLHEP::rad;
        }
 
        default:
            // Unknown model: no randomization.
            return center;
    }
}
 
// ---------------------------------------------------------------------------
//  pretty printer
// ---------------------------------------------------------------------------
std::ostream& operator<<(std::ostream& os, const Gparticle& gp) {
    using std::left;
    using std::right;
    using std::setw;
 
    constexpr int label_w = 15; // width for the field name (with ':')
    constexpr int value_w = 12; // width for the main column
 
    // helper: plain value
    auto show = [&](const std::string& label, const auto& value) {
        os << left << setw(label_w) << label << ' '
            << setw(value_w) << right << setw(value_w) << value << '\n';
    };
 
    // helper: double value with N decimals
    auto showf = [&](const std::string& label, double value, int prec = 3) {
        std::streamsize old_prec  = os.precision(); // save current
        auto            old_flags = os.flags();     // save flags
 
        os << left << setw(label_w) << label << ' '
            << right << setw(value_w) << std::fixed
            << std::setprecision(prec) << value << '\n';
 
        os.precision(old_prec); // restore
        os.flags(old_flags);
    };
 
    // helper: value ± error (both doubles)
    auto show_pm = [&](const std::string& label,
                       double             val, double err,
                       int                prec = 3) {
        std::streamsize old_prec  = os.precision();
        auto            old_flags = os.flags();
 
        os << left << setw(label_w) << label << ' '
            << right << setw(value_w) << std::fixed << setw(value_w)
            << std::setprecision(prec) << val
            << "  ± " << std::setprecision(prec) << err << '\n';
 
        os.precision(old_prec);
        os.flags(old_flags);
    };
 
    // -----------------------------------------------------------------------
    //  header block
    // -----------------------------------------------------------------------
    os << '\n'
        << " ┌─────────────────────────────────────────────────┐\n"
        << " │ GParticle                                       │\n"
        << " └─────────────────────────────────────────────────┘\n";
 
    // -----------------------------------------------------------------------
    //  fields
    // -----------------------------------------------------------------------
    os << left << setw(label_w) << " name:" << right << setw(value_w)
        << gp.name << "(pid " << gp.pid << ")\n";
 
    show(" multiplicity:", std::to_string(gp.multiplicity));
    showf(" mass [MeV]:", gp.get_mass());
 
    show_pm(" p [MeV]:",
            gp.p / CLHEP::MeV,
            gp.delta_p / CLHEP::MeV);
 
    show(" p model:", to_string(gp.randomMomentumModel));
 
    show_pm(" theta [deg]:",
            gp.theta / CLHEP::deg,
            gp.delta_theta / CLHEP::deg);
 
    show(" theta model:", to_string(gp.randomThetaModel));
 
    show_pm(" phi  [deg]:",
            gp.phi / CLHEP::deg,
            gp.delta_phi / CLHEP::deg);
 
    os << left << setw(label_w) << " vertex [cm]:" << ' '
        << gp.v << "  ± " << gp.delta_v << '\n';
 
    show(" vertex model:", to_string(gp.randomVertexModel));
 
    return os;
}
 
 
int Gparticle::get_pdg_id() {
    auto particleTable = G4ParticleTable::GetParticleTable();
 
    if (particleTable) {
        auto particleDef = particleTable->FindParticle(name);
 
        if (particleDef != nullptr) { return particleDef->GetPDGEncoding(); }
        else {
            log->error(
                gparticle::ERR_GPARTICLENOTFOUND, "Particle <%1> not found in G4ParticleTable* %2", name,
                particleTable);
        }
    }
    else {
        log->error(
            gparticle::ERR_GPARTICLETABLENOTFOUND, "G4ParticleTable not found - G4ParticleGun*: %1",
            particleTable);
    }
}
 
 
double Gparticle::get_mass() const {
    auto particleTable = G4ParticleTable::GetParticleTable();
 
    if (particleTable) {
        auto particleDef = particleTable->FindParticle(name);
 
        if (particleDef) {
            double mass = particleDef->GetPDGMass();
            return mass;
        }
    }
    return 0;
}