barrel_hcal/scripts/hcal_barrel_particles_gen.cxx

0001 //////////////////////////////////////////////////////////////
0002 // HCAL Barrel detector
0003 // Generate particles with particle gun
0004 // J.Kim 04/02/21
0005 // M.Zurek 05/05/21
0006 // W.Deconinck 05/27/21
0007 //////////////////////////////////////////////////////////////
0008 #include "HepMC3/GenEvent.h"
0009 #include "HepMC3/Print.h"
0010 #include "HepMC3/ReaderAscii.h"
0011 #include "HepMC3/WriterAscii.h"
0012
0013 #include "TMath.h"
0014 #include "TRandom.h"
0015
0016 #include <cmath>
0017 #include <iostream>
0018 #include <fstream>
0019 #include <math.h>
0020 #include <random>
0021 #include <cstdlib>
0022 #include <fmt/core.h>
0023
0024 #include "hcal_barrel_common_functions.h"
0025
0026 using namespace HepMC3;
0027
0028 void hcal_barrel_particles_gen(int n_events = 1e6, double e_start = 0.0, double e_end = 20.0, std::string particle_name = "muon") {
0029   std::string out_fname;
0030   auto env_fname = getenv("JUGGLER_GEN_FILE");
0031   if (env_fname != nullptr)
0032     out_fname = env_fname;
0033   else
0034     out_fname = fmt::format("./data/hcal_barrel_{}.hepmc", particle_name);
0035   WriterAscii hepmc_output(out_fname);
0036   int events_parsed = 0;
0037   GenEvent evt(Units::GEV, Units::MM);
0038
0039   // Random number generator
0040   TRandom* r1 = new TRandom();
0041
0042   // Constraining the solid angle, but larger than that subtended by the
0043   // detector
0044   // https://indico.bnl.gov/event/7449/contributions/35966/attachments/27177/41430/EIC-DWG-Calo-03192020.pdf
0045   // See a figure on slide 26
0046   double cos_theta_min = std::cos(M_PI * (45.0 / 180.0));
0047   double cos_theta_max = std::cos(M_PI * (135.0 / 180.0));
0048
0049   for (events_parsed = 0; events_parsed < n_events; events_parsed++) {
0050     // FourVector(px,py,pz,e,pdgid,status)
0051     // type 4 is beam
0052     // pdgid 11 - electron
0053     // pdgid 2212 - proton
0054     GenParticlePtr p1 = std::make_shared<GenParticle>(FourVector(0.0, 0.0, 10.0, 10.0), 11, 4);
0055     GenParticlePtr p2 = std::make_shared<GenParticle>(FourVector(0.0, 0.0, 0.0, 0.938), 2212, 4);
0056
0057     // Define momentum
0058     Double_t p        = r1->Uniform(e_start, e_end);
0059     Double_t phi      = r1->Uniform(0.0, 2.0 * M_PI);
0060     Double_t costheta = r1->Uniform(cos_theta_min, cos_theta_max);
0061     Double_t theta    = std::acos(costheta);
0062     Double_t px       = p * std::cos(phi) * std::sin(theta);
0063     Double_t py       = p * std::sin(phi) * std::sin(theta);
0064     Double_t pz       = p * std::cos(theta);
0065
0066     // type 1 is final state
0067     auto [id, mass] = extract_particle_parameters(particle_name);
0068     GenParticlePtr p3 = std::make_shared<GenParticle>(FourVector(px, py, pz, sqrt(p * p + (mass * mass))), id, 1);
0069
0070     GenVertexPtr v1 = std::make_shared<GenVertex>();
0071     v1->add_particle_in(p1);
0072     v1->add_particle_in(p2);
0073     v1->add_particle_out(p3);
0074     evt.add_vertex(v1);
0075
0076     if (events_parsed == 0) {
0077       std::cout << "First event: " << std::endl;
0078       Print::listing(evt);
0079     }
0080
0081     hepmc_output.write_event(evt);
0082     if (events_parsed % 10000 == 0) {
0083       std::cout << "Event: " << events_parsed << std::endl;
0084     }
0085     evt.clear();
0086   }
0087   hepmc_output.close();
0088   std::cout << "Events parsed and written: " << events_parsed << std::endl;
0089 }
0090