barrel_ecal/scripts/emcal_barrel_particles_gen.cxx

0001 //////////////////////////////////////////////////////////////
0002 // EMCAL Barrel detector
0003 // Generate particles with particle gun
0004 // J.Kim 04/02/21
0005 // M.Zurek 05/05/21
0006 //////////////////////////////////////////////////////////////
0007 #include "HepMC3/GenEvent.h"
0008 #include "HepMC3/Print.h"
0009 #include "HepMC3/ReaderAscii.h"
0010 #include "HepMC3/WriterAscii.h"
0011
0012 #include "TMath.h"
0013 #include "TRandom.h"
0014
0015 #include <cmath>
0016 #include <iostream>
0017 #include <math.h>
0018 #include <random>
0019 #include <fmt/core.h>
0020
0021 #include "emcal_barrel_common_functions.h"
0022
0023 using namespace HepMC3;
0024
0025 void emcal_barrel_particles_gen(int n_events = 1e6, double e_start = 0.0, double e_end = 20.0, std::string particle_name = "electron") {
0026   std::string out_fname = fmt::format("./data/{}", std::getenv("JUGGLER_GEN_FILE"));
0027   WriterAscii hepmc_output(out_fname);
0028   int events_parsed = 0;
0029   GenEvent evt(Units::GEV, Units::MM);
0030
0031   // Random number generator
0032   TRandom* r1 = new TRandom();
0033
0034   // Constraining the solid angle, but larger than that subtended by the
0035   // detector
0036   // https://indico.bnl.gov/event/7449/contributions/35966/attachments/27177/41430/EIC-DWG-Calo-03192020.pdf
0037   // See a figure on slide 26
0038   double cos_theta_min = std::cos(M_PI * (45.0 / 180.0));
0039   double cos_theta_max = std::cos(M_PI * (135.0 / 180.0));
0040
0041   for (events_parsed = 0; events_parsed < n_events; events_parsed++) {
0042     // FourVector(px,py,pz,e,pdgid,status)
0043     // type 4 is beam
0044     // pdgid 11 - electron
0045     // pdgid 2212 - proton
0046     GenParticlePtr p1 = std::make_shared<GenParticle>(FourVector(0.0, 0.0, 10.0, 10.0), 11, 4);
0047     GenParticlePtr p2 = std::make_shared<GenParticle>(FourVector(0.0, 0.0, 0.0, 0.938), 2212, 4);
0048
0049     // Define momentum
0050     Double_t p        = r1->Uniform(e_start, e_end);
0051     Double_t phi      = r1->Uniform(0.0, 2.0 * M_PI);
0052     Double_t costheta = r1->Uniform(cos_theta_min, cos_theta_max);
0053     Double_t theta    = std::acos(costheta);
0054     Double_t px       = p * std::cos(phi) * std::sin(theta);
0055     Double_t py       = p * std::sin(phi) * std::sin(theta);
0056     Double_t pz       = p * std::cos(theta);
0057
0058     // type 1 is final state
0059     auto [id, mass] = extract_particle_parameters(particle_name);
0060     GenParticlePtr p3 = std::make_shared<GenParticle>(FourVector(px, py, pz, sqrt(p * p + (mass * mass))), id, 1);
0061
0062     GenVertexPtr v1 = std::make_shared<GenVertex>();
0063     v1->add_particle_in(p1);
0064     v1->add_particle_in(p2);
0065     v1->add_particle_out(p3);
0066     evt.add_vertex(v1);
0067
0068     if (events_parsed == 0) {
0069       std::cout << "First event: " << std::endl;
0070       Print::listing(evt);
0071     }
0072
0073     hepmc_output.write_event(evt);
0074     if (events_parsed % 10000 == 0) {
0075       std::cout << "Event: " << events_parsed << std::endl;
0076     }
0077     evt.clear();
0078   }
0079   hepmc_output.close();
0080   std::cout << "Events parsed and written: " << events_parsed << std::endl;
0081 }
0082