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//
//
// $Id$
// GEANT4 tag $Name$
//
//
//  This is the standard right-hand side for equation of motion.
//
//  The only case another is required is when using a moving reference
//  frame ... or extending the class to include additional Forces,
//  eg an electric field
//
//  10.11.98   V.Grichine
//
// -------------------------------------------------------------------


#include "LEMuSREqMagElectricField.hh"
#include "globals.hh"

void
LEMuSREqMagElectricField::SetChargeMomentumMass(G4double particleCharge, // e+ units
                                            G4double,
                                            G4double particleMass)
{
   fElectroMagCof =  eplus*particleCharge*c_light ;
   fMassCof = particleMass*particleMass ;
}



void
LEMuSREqMagElectricField::EvaluateRhsGivenB(const G4double y[],
                                        const G4double Field[],
                                              G4double dydx[] ) const
{

   // Components of y:
   //    0-2 dr/ds,
   //    3-5 dp/ds - momentum derivatives

   G4double pSquared = y[3]*y[3] + y[4]*y[4] + y[5]*y[5] ;

   G4double Energy   = sqrt( pSquared + fMassCof );
   G4double cof2     = Energy/c_light ;

   G4double pModuleInverse  = 1.0/sqrt(pSquared) ;

   //  G4double inverse_velocity = Energy * c_light * pModuleInverse;
   G4double inverse_velocity = Energy * pModuleInverse / c_light;

   G4double cof1     = fElectroMagCof*pModuleInverse ;

   //  G4double vDotE = y[3]*Field[3] + y[4]*Field[4] + y[5]*Field[5] ;


   dydx[0] = y[3]*pModuleInverse ;
   dydx[1] = y[4]*pModuleInverse ;
   dydx[2] = y[5]*pModuleInverse ;

   dydx[3] = cof1*(cof2*Field[3] + (y[4]*Field[2] - y[5]*Field[1])) ;

   dydx[4] = cof1*(cof2*Field[4] + (y[5]*Field[0] - y[3]*Field[2])) ;

   dydx[5] = cof1*(cof2*Field[5] + (y[3]*Field[1] - y[4]*Field[0])) ;

   // Lab Time of flight
   dydx[7] = inverse_velocity;
   return ;
}
