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//////////////////////////////////////////////////////////////
// EMCAL Barrel detector
// Single Electron dataset
// J.KIM 04/02/2021
//////////////////////////////////////////////////////////////
#include "HepMC3/GenEvent.h"
#include "HepMC3/Print.h"
#include "HepMC3/ReaderAscii.h"
#include "HepMC3/WriterAscii.h"
#include <TMath.h>
#include <cmath>
#include <iostream>
#include <math.h>
#include <random>
using namespace HepMC3;
void emcal_barrel_electrons(int n_events = 1e6, double e_start = 0.0, double e_end = 30.0, const char* out_fname = "./data/emcal_barrel_electrons.hepmc") {
WriterAscii hepmc_output(out_fname);
int events_parsed = 0;
GenEvent evt(Units::GEV, Units::MM);
// Random number generator
TRandom* r1 = new TRandom();
// Constraining the solid angle, but larger than that subtended by the
// detector
// https://indico.bnl.gov/event/7449/contributions/35966/attachments/27177/41430/EIC-DWG-Calo-03192020.pdf
// See a figure on slide 26
double cos_theta_min = std::cos(M_PI * (45.0 / 180.0));
double cos_theta_max = std::cos(M_PI * (135.0 / 180.0));
for (events_parsed = 0; events_parsed < n_events; events_parsed++) {
// FourVector(px,py,pz,e,pdgid,status)
// type 4 is beam
// pdgid 11 - electron
// pdgid 111 - pi0
// pdgid 2212 - proton
GenParticlePtr p1 = std::make_shared<GenParticle>(FourVector(0.0, 0.0, 10.0, 10.0), 11, 4);
GenParticlePtr p2 = std::make_shared<GenParticle>(FourVector(0.0, 0.0, 0.0, 0.938), 2212, 4);
// Define momentum
Double_t p = r1->Uniform(e_start, e_end);
Double_t phi = r1->Uniform(0.0, 2.0 * M_PI);
Double_t costheta = r1->Uniform(cos_theta_min, cos_theta_max);
Double_t theta = std::acos(costheta);
Double_t px = p * std::cos(phi) * std::sin(theta);
Double_t py = p * std::sin(phi) * std::sin(theta);
Double_t pz = p * std::cos(theta);
// Generates random vectors, uniformly distributed over the surface of a
// sphere of given radius, in this case momentum.
// r1->Sphere(px, py, pz, p);
// type 1 is final state
// pdgid 11 - electron 0.510 MeV/c^2
GenParticlePtr p3 = std::make_shared<GenParticle>(FourVector(px, py, pz, sqrt(p * p + (0.000511 * 0.000511))), 11, 1);
GenVertexPtr v1 = std::make_shared<GenVertex>();
v1->add_particle_in(p1);
v1->add_particle_in(p2);
v1->add_particle_out(p3);
evt.add_vertex(v1);
if (events_parsed == 0) {
std::cout << "First event: " << std::endl;
Print::listing(evt);
}
hepmc_output.write_event(evt);
if (events_parsed % 10000 == 0) {
std::cout << "Event: " << events_parsed << std::endl;
}
evt.clear();
}
hepmc_output.close();
std::cout << "Events parsed and written: " << events_parsed << std::endl;
}