field/field05/README.md

0001 \page Examplefield05 Example field05
0002
0003  This example checks so-called "spin-frozen" condition
0004  There is a good example article hep-ph/0012087v1.
0005  This article discusses about how to cancel the muon g-2 precession by
0006  applying an electric field.
0007
0008  - 1) beta is muon velocity,
0009  - 2) B is an uniform magnetic field and vec{beta}.vec{B}=0,
0010     "." means scalar product,
0011  - 3) Radial electric field (E) in the lab frame and vec{beta}.vec{E}=0,
0012  - 4) a=(g-2)/2 is muon anomalous magnetic moment.
0013
0014  The required electric field to cancel the g-2 precession is,
0015 ```cpp
0016 E = a*B*light_c*gamma**2*beta
0017 ```
0018
0019  In case of gamma=5 and B=0.24 Tesla, the required electric field is
0020 ```cpp
0021 E = 2 MV/m
0022 ```
0023
0024  "Spin-frozen" happens when spin rotation cycle and muon rotation cycle
0025  are same. In this case, both cycles should be 149.5 nsec.
0026
0027  See also:
0028  http://research.kek.jp/people/hiromi/MyHomePage/G-2_work_files/SpinStudyinEMfieldByGeant4.pdf
0029
0030  Credit goes to Hiromi Iinuma from KEK.
0031
0032 ## main()
0033
0034  See main() in field05.cc.
0035
0036 ## GEOMETRY DEFINITION
0037
0038  As simple world G4Box with a G4ElectroMagneticField      \n
0039  propagating both spin and momentum (G4EqEMFieldWithSpin) \n
0040  with G4ClassicalRK4(fEquation,12) and                    \n
0041  Bz = 0.24*tesla;                                         \n
0042  Er = 2.113987E+6*volt/m;
0043
0044 ## AN EVENT: THE PRIMARY GENERATOR
0045
0046  Use mu+ G4ParticleGun with Pmu = 517.6*MeV/c            \n
0047  and aligned spin and momentum direction
0048
0049 ## PHYSICS
0050
0051 ```cpp
0052 RegisterPhysics(new G4SpinDecayPhysics());
0053 RegisterPhysics(new G4StepLimiterPhysics());
0054 ```
0055
0056  - G4SpinDecayPhysics defines muon decay modes with spin,
0057  - G4StepLimiterPhysics defines G4StepLimiter and G4UserSpecialCuts.
0058
0059 ## User Action Classes
0060
0061 - F05SteppingAction:
0062
0063   G4Exception when the cosine of the angle between
0064   the spin and the momentum is < (1.-1.E-7)
0065
0066 ## HOW TO START ?
0067
0068  - Execute field05 in 'batch' mode from macro files e.g.
0069 ```
0070 % ./field05 field05.in > field.out &
0071 ```
0072
0073  - Execute field05 in 'interactive' mode with visualization e.g.
0074 ```
0075 % ./field05
0076 ....
0077 Idle> type your commands, for example:
0078 Idle> run/beamOn 1
0079 ....
0080 ```