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ParticleTests.cpp
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1 // This file is part of the Acts project.
2 //
3 // Copyright (C) 2018-2020 CERN for the benefit of the Acts project
4 //
5 // This Source Code Form is subject to the terms of the Mozilla Public
6 // License, v. 2.0. If a copy of the MPL was not distributed with this
7 // file, You can obtain one at http://mozilla.org/MPL/2.0/.
8 
9 #include <boost/test/unit_test.hpp>
10 
11 #include "Acts/Definitions/PdgParticle.hpp"
12 #include "Acts/Definitions/Units.hpp"
13 #include "Acts/Tests/CommonHelpers/FloatComparisons.hpp"
14 #include "ActsFatras/EventData/Barcode.hpp"
15 #include "ActsFatras/EventData/Particle.hpp"
16 
17 #include <cmath>
18 #include <limits>
19 
20 using Acts::PdgParticle;
21 using ActsFatras::Barcode;
22 using ActsFatras::Particle;
23 using namespace Acts::UnitLiterals;
24 
25 namespace {
26 constexpr auto eps = std::numeric_limits<Particle::Scalar>::epsilon();
27 }
28 
29 BOOST_AUTO_TEST_SUITE(FatrasParticle)
30 
31 BOOST_AUTO_TEST_CASE(Construct) {
32  const auto pid = Barcode().setVertexPrimary(1).setParticle(42);
33  const auto particle = Particle(pid, PdgParticle::eProton, 1_e, 1_GeV);
34 
35  BOOST_CHECK_EQUAL(particle.particleId(), pid);
36  BOOST_CHECK_EQUAL(particle.pdg(), PdgParticle::eProton);
37  // particle is at rest at the origin
38  BOOST_CHECK_EQUAL(particle.fourPosition(), Particle::Vector4::Zero());
39  BOOST_CHECK_EQUAL(particle.position(), Particle::Vector3::Zero());
40  BOOST_CHECK_EQUAL(particle.time(), Particle::Scalar(0));
41  BOOST_CHECK_EQUAL(particle.fourPosition().x(), particle.position().x());
42  BOOST_CHECK_EQUAL(particle.fourPosition().y(), particle.position().y());
43  BOOST_CHECK_EQUAL(particle.fourPosition().z(), particle.position().z());
44  BOOST_CHECK_EQUAL(particle.fourPosition().w(), particle.time());
45  // particle direction is undefined, but must be normalized
46  CHECK_CLOSE_REL(particle.direction().norm(), 1, eps);
47  BOOST_CHECK_EQUAL(particle.transverseMomentum(), Particle::Scalar(0));
48  BOOST_CHECK_EQUAL(particle.absoluteMomentum(), Particle::Scalar(0));
49  // particle is created at rest and thus not alive
50  BOOST_CHECK(not particle.isAlive());
51 }
52 
53 BOOST_AUTO_TEST_CASE(CorrectEnergy) {
54  const auto pid = Barcode().setVertexPrimary(1).setParticle(42);
55  auto particle = Particle(pid, PdgParticle::eProton, 1_e, 1_GeV)
56  .setDirection(Particle::Vector3::UnitX())
57  .setAbsoluteMomentum(2_GeV);
58 
59  BOOST_CHECK_EQUAL(particle.mass(), 1_GeV);
60  // check that the particle has some input energy
61  BOOST_CHECK_EQUAL(particle.fourMomentum().x(), 2_GeV);
62  BOOST_CHECK_EQUAL(particle.fourMomentum().y(), 0_GeV);
63  BOOST_CHECK_EQUAL(particle.fourMomentum().z(), 0_GeV);
64  BOOST_CHECK_EQUAL(particle.fourMomentum().w(), std::hypot(1_GeV, 2_GeV));
65  BOOST_CHECK_EQUAL(particle.transverseMomentum(), 2_GeV);
66  BOOST_CHECK_EQUAL(particle.absoluteMomentum(), 2_GeV);
67  BOOST_CHECK_EQUAL(particle.energy(), std::hypot(1_GeV, 2_GeV));
68  // particle direction must be normalized
69  CHECK_CLOSE_REL(particle.direction().norm(), 1, eps);
70 
71  // loose some energy
72  particle.correctEnergy(-100_MeV);
73  BOOST_CHECK_LT(particle.transverseMomentum(), 2_GeV);
74  BOOST_CHECK_LT(particle.absoluteMomentum(), 2_GeV);
75  BOOST_CHECK_EQUAL(particle.energy(),
76  Particle::Scalar(std::hypot(1_GeV, 2_GeV) - 100_MeV));
77  CHECK_CLOSE_REL(particle.direction().norm(), 1, eps);
78  // particle is still alive
79  BOOST_CHECK(particle.isAlive());
80 
81  // loose some more energy
82  particle.correctEnergy(-200_MeV);
83  BOOST_CHECK_LT(particle.transverseMomentum(), 2_GeV);
84  BOOST_CHECK_LT(particle.absoluteMomentum(), 2_GeV);
85  BOOST_CHECK_EQUAL(particle.energy(),
86  Particle::Scalar(std::hypot(1_GeV, 2_GeV) - 300_MeV));
87  CHECK_CLOSE_REL(particle.direction().norm(), 1, eps);
88  // particle is still alive
89  BOOST_CHECK(particle.isAlive());
90 
91  // loose a lot of energy
92  particle.correctEnergy(-3_GeV);
93  BOOST_CHECK_EQUAL(particle.transverseMomentum(), Particle::Scalar(0));
94  BOOST_CHECK_EQUAL(particle.absoluteMomentum(), Particle::Scalar(0));
95  BOOST_CHECK_EQUAL(particle.energy(), particle.mass());
96  CHECK_CLOSE_REL(particle.direction().norm(), 1, eps);
97  // particle is not alive anymore
98  BOOST_CHECK(not particle.isAlive());
99 
100  // lossing even more energy does nothing
101  particle.correctEnergy(-10_GeV);
102  BOOST_CHECK_EQUAL(particle.transverseMomentum(), Particle::Scalar(0));
103  BOOST_CHECK_EQUAL(particle.absoluteMomentum(), Particle::Scalar(0));
104  BOOST_CHECK_EQUAL(particle.energy(), particle.mass());
105  CHECK_CLOSE_REL(particle.direction().norm(), 1, eps);
106  // particle is still not alive
107  BOOST_CHECK(not particle.isAlive());
108 }
109 
110 BOOST_AUTO_TEST_SUITE_END()