Newer
Older
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
#include "HepMC3/GenEvent.h"
#include "HepMC3/ReaderAscii.h"
#include "HepMC3/WriterAscii.h"
#include "HepMC3/Print.h"
#include <iostream>
#include<random>
#include<cmath>
#include <math.h>
#include <TMath.h>
using namespace HepMC3;
/** Generate electrons in the central region.
* This is for testing detectors in the "barrel" region.
*/
void gen_central_electrons(int n_events = 100,
const char* out_fname = "central_electrons.hepmc")
{
double cos_theta_min = std::cos( 70.0*(M_PI/180.0));
double cos_theta_max = std::cos(110.0*(M_PI/180.0));
WriterAscii hepmc_output(out_fname);
int events_parsed = 0;
GenEvent evt(Units::GEV, Units::MM);
// Random number generator
TRandom *r1 = new TRandom();
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(1.0, 10.0);
Double_t phi = r1->Uniform(0.0, 2.0 * M_PI);
Double_t costh = r1->Uniform(cos_theta_min, cos_theta_max);
Double_t th = std::acos(costh);
Double_t px = p * std::cos(phi) * std::sin(th);
Double_t py = p * std::sin(phi) * std::sin(th);
Double_t pz = p * std::cos(th);
// Generates random vectors, uniformly distributed over the surface of a
// sphere of given radius, in this case momentum.
// r1->Sphere(px, py, pz, p);
//std::cout << std::sqrt(px*px + py*py + pz*pz) - p << " is zero? \n";
// 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;
}