//$Id$

///\file "field/field05/.README.txt"
///\brief Example field05 README page

/*! \page Examplefield05 Example field05

 This example checks so-called "spin-frozen" condition
 There is a good example article hep-ph/0012087v1.
 This article discusses about how to cancel the muon g-2 precession by
 applying an electric field.

 - 1) beta is muon velocity,
 - 2) B is an uniform magnetic field and vec{beta}.vec{B}=0,
    "." means scalar product,
 - 3) Radial electric field (E) in the lab frame and vec{beta}.vec{E}=0,
 - 4) a=(g-2)/2 is muon anomalous magnetic moment.

 The required electric field to cancel the g-2 precession is,
\verbatim
E=a*B*light_c*gamma**2*beta.
\endverbatim

 In case of gamma=5 and B=0.24 Tesla, the required electric field is 
\verbatim
E=2 MV/m.
\endverbatim

 "Spin-frozen" happens when spin rotation cycle and muon rotation cycle 
 are same. In this case, both cycles should be 149.5 nsec.

 See also:
 http://research.kek.jp/people/hiromi/MyHomePage/G-2_work_files/SpinStudyinEMfieldByGeant4.pdf

 Credit goes to Hiromi Iinuma from KEK.

Classes Used

\section field05_s1 main ()

 See field05.cc.

\section field05_s2 GEOMETRY DEFINITION

 as simple world G4Box with a G4ElectroMagneticField      \n
 propagating both spin and momentum (G4EqEMFieldWithSpin) \n
 with G4ClassicalRK4(fEquation,12) and                    \n
 Bz = 0.24*tesla;                                         \n
 Er = 2.113987E+6*volt/m;

\section field05_s3 AN EVENT: THE PRIMARY GENERATOR

 use mu+ G4ParticleGun with Pmu = 517.6*MeV/c            \n
 and aligned spin and momentum direction

\section field05_s4 PHYSICS
\verbatim
RegisterPHysics(new G4DecayPhysics());
RegisterPhysics(new G4StepLimiterPhysics());

G4VModularPhysicsList::ConstructParticle();
\endverbatim

 and replace muon decay modes with those with spin:
- G4MuonDecayChannelWithSpin
- G4MuonRadiativeDecayChannelWithSpin

 and replace G4Decay with
- G4DecayWithSpin process for the muon
- G4PionDecayMakeSpin process for the pion

 G4StepLimiterPhysics defines G4StepLimiter and G4UserSpecialCuts

\section field05_s5 User Action Classes

 SteppingAction: \n
 G4Exception when the cosine of the angle between
 the spin and the momentum is < (1.-1.E-7)

\section field05_s6 HOW TO START ?

 - Execute field05 in 'batch' mode from macro files e.g.
\verbatim
% field05 field05.in > field.out &
\endverbatim

 - Execute field05 in 'interactive' mode with visualization e.g.
\verbatim
% field05
....
Idle> type your commands, for example:
Idle> run/beamOn 1
....
\endverbatim
*/
