| Geant4 Cross Reference |
1 1
2 ========================================= 2 =========================================================
3 Geant4 - an Object-Oriented Toolkit for S 3 Geant4 - an Object-Oriented Toolkit for Simulation in HEP
4 ========================================= 4 =========================================================
5 5
6 6
7 7
8 field05 Example 8 field05 Example
9 --------------- 9 ---------------
10 10
11 This example checks so-called "spin-froze 11 This example checks so-called "spin-frozen" condition
12 There is a good example article hep-ph/00 12 There is a good example article hep-ph/0012087v1.
13 This article discusses about how to cance 13 This article discusses about how to cancel the muon g-2 precession by
14 applying an electric field. 14 applying an electric field.
15 15
16 1) beta is muon velocity, 16 1) beta is muon velocity,
17 2) B is an uniform magnetic field and \ve 17 2) B is an uniform magnetic field and \vec{beta}.\vec{B}=0,
18 "." means scalar product, 18 "." means scalar product,
19 3) Radial electric field (E) in the lab f 19 3) Radial electric field (E) in the lab frame and \vec{beta}.\vec{E}=0,
20 4) a=(g-2)/2 is muon anomalous magnetic m 20 4) a=(g-2)/2 is muon anomalous magnetic moment.
21 21
22 The required electric field to cancel the 22 The required electric field to cancel the g-2 precession is,
23 E=a*B*light_c*gamma**2*beta. 23 E=a*B*light_c*gamma**2*beta.
24 24
25 In case of gamma=5 and B=0.24 Tesla, the << 25 In case of gamma=5 and B=0.24 Tesla, the required electric field is
26 E=2 MV/m. 26 E=2 MV/m.
27 27
28 "Spin-frozen" happens when spin rotation << 28 "Spin-frozen" happens when spin rotation cycle and muon rotation cycle
29 are same. In this case, both cycles shoul 29 are same. In this case, both cycles should be 149.5 nsec.
30 30
31 See also: 31 See also:
32 http://research.kek.jp/people/hiromi/MyHo 32 http://research.kek.jp/people/hiromi/MyHomePage/G-2_work_files/SpinStudyinEMfieldByGeant4.pdf
33 33
34 34
35 Credit goes to Hiromi Iinuma from KEK. << 35 Credit goes to Hiromi Iinuma from KEK
36 36
37 ************** 37 **************
38 *Classes Used* 38 *Classes Used*
39 ************** 39 **************
40 40
41 1 - main() 41 1 - main()
42 42
43 See field05.cc. <<
44 <<
45 2- GEOMETRY DEFINITION 43 2- GEOMETRY DEFINITION
46 44
47 as simple world G4Box with a G4ElectroMagn 45 as simple world G4Box with a G4ElectroMagneticField
48 propagating both spin and momentum (G4EqEM 46 propagating both spin and momentum (G4EqEMFieldWithSpin)
49 with G4ClassicalRK4(fEquation,12) and 47 with G4ClassicalRK4(fEquation,12) and
50 Bz = 0.24*tesla; 48 Bz = 0.24*tesla;
51 Er = 2.113987E+6*volt/m; 49 Er = 2.113987E+6*volt/m;
52 50
53 3- AN EVENT: THE PRIMARY GENERATOR 51 3- AN EVENT: THE PRIMARY GENERATOR
54 52
55 use mu+ G4ParticleGun with Pmu = 517.6*MeV 53 use mu+ G4ParticleGun with Pmu = 517.6*MeV/c
56 and aligned spin and momentum direction 54 and aligned spin and momentum direction
57 55
58 4- PHYSICS 56 4- PHYSICS
59 57
60 RegisterPhysics(new G4SpinDecayPhysics()); << 58 RegisterPhysics(new G4DecayPhysics());
61 RegisterPhysics(new G4StepLimiterPhysics() << 59 RegisterPhysics(new F05ExtraPhysics());
>> 60
>> 61 G4VModularPhysicsList::ConstructParticle();
62 62
63 G4SpinDecayPhysics defines muon decay mode << 63 and replace muon decay modes with those with spin:
64 G4StepLimiterPhysics defines G4StepLimiter << 64 G4MuonDecayChannelWithSpin
>> 65 G4MuonRadiativeDecayChannelWithSpin
>> 66 and replace G4Decay with
>> 67 G4DecayWithSpin process for the muon
>> 68 G4PionDecayMakeSpin process for the pion
>> 69
>> 70 F05ExtraPhysics defines G4StepLimiter and G4UserSpecialCuts
65 71
66 5- User Action Classes 72 5- User Action Classes
67 73
68 SteppingAction: 74 SteppingAction:
69 G4Exception when the cosine of the 75 G4Exception when the cosine of the angle between
70 the spin and the momentum is < (1. 76 the spin and the momentum is < (1.-1.E-7)
71 77
72 6- HOW TO START ? 78 6- HOW TO START ?
73 79
74 - Execute field05 in 'batch' mode from << 80 - compile and link to generate an executable
75 % field05 field05.in > field.o << 81 % cd $G4INSTALL/example/extended/field/field05
>> 82 % gmake
>> 83
>> 84 - execute field05 in 'batch' mode from macro files e.g.
>> 85 % $(G4INSTALL)/bin/$(G4SYSTEM)/field05 field05.in > field.out &
76 86
77 - Execute field05 in 'interactive' mod << 87 - execute field05 in 'interactive' mode with visualization e.g.
78 % field05 << 88 % $(G4INSTALL)/bin/$(G4SYSTEM)/field05
79 .... 89 ....
80 Idle> type your commands, for 90 Idle> type your commands, for example:
81 Idle> run/beamOn 1 91 Idle> run/beamOn 1
82 .... 92 ....