| Geant4 Cross Reference |
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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. 43 See field05.cc.
44 44
45 2- GEOMETRY DEFINITION 45 2- GEOMETRY DEFINITION
46 46
47 as simple world G4Box with a G4ElectroMagn 47 as simple world G4Box with a G4ElectroMagneticField
48 propagating both spin and momentum (G4EqEM 48 propagating both spin and momentum (G4EqEMFieldWithSpin)
49 with G4ClassicalRK4(fEquation,12) and 49 with G4ClassicalRK4(fEquation,12) and
50 Bz = 0.24*tesla; 50 Bz = 0.24*tesla;
51 Er = 2.113987E+6*volt/m; 51 Er = 2.113987E+6*volt/m;
52 52
53 3- AN EVENT: THE PRIMARY GENERATOR 53 3- AN EVENT: THE PRIMARY GENERATOR
54 54
55 use mu+ G4ParticleGun with Pmu = 517.6*MeV 55 use mu+ G4ParticleGun with Pmu = 517.6*MeV/c
56 and aligned spin and momentum direction 56 and aligned spin and momentum direction
57 57
58 4- PHYSICS 58 4- PHYSICS
59 59
60 RegisterPhysics(new G4SpinDecayPhysics()); 60 RegisterPhysics(new G4SpinDecayPhysics());
61 RegisterPhysics(new G4StepLimiterPhysics() 61 RegisterPhysics(new G4StepLimiterPhysics());
62 62
63 G4SpinDecayPhysics defines muon decay mode 63 G4SpinDecayPhysics defines muon decay modes with spin,
64 G4StepLimiterPhysics defines G4StepLimiter 64 G4StepLimiterPhysics defines G4StepLimiter and G4UserSpecialCuts.
65 65
66 5- User Action Classes 66 5- User Action Classes
67 67
68 SteppingAction: 68 SteppingAction:
69 G4Exception when the cosine of the 69 G4Exception when the cosine of the angle between
70 the spin and the momentum is < (1. 70 the spin and the momentum is < (1.-1.E-7)
71 71
72 6- HOW TO START ? 72 6- HOW TO START ?
73 73
74 - Execute field05 in 'batch' mode from 74 - Execute field05 in 'batch' mode from macro files e.g.
75 % field05 field05.in > field.o 75 % field05 field05.in > field.out &
76 76
77 - Execute field05 in 'interactive' mod 77 - Execute field05 in 'interactive' mode with visualization e.g.
78 % field05 78 % field05
79 .... 79 ....
80 Idle> type your commands, for 80 Idle> type your commands, for example:
81 Idle> run/beamOn 1 81 Idle> run/beamOn 1
82 .... 82 ....