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//
// G4Mag_SpinEqRhs
//
// Class description:
//
// This is the equation of motion for a particle with spin in a pure
// magnetic field. The three components of the particle's spin are
// treated utilising BMT equation.

// Authors: John Apostolakis (CERN) & Peter Gumplinger (TRIUMF), 08.02.1999
// --------------------------------------------------------------------
#ifndef G4MAG_SPIN_EQRHS_HH
#define G4MAG_SPIN_EQRHS_HH

#include "G4Types.hh"
#include "G4Mag_EqRhs.hh"
#include "G4ChargeState.hh"

class G4MagneticField;

/**
 * @brief G4Mag_SpinEqRhs defines the equation of motion for a particle with
 * spin in a pure magnetic field. The three components of the particle's spin
 * are treated utilising BMT equation.
 */

class G4Mag_SpinEqRhs : public G4Mag_EqRhs
{
  public:

    /**
     * Constructor for G4Mag_SpinEqRhs.
     *  @param[in] MagField Pointer to the associated magnetic field.
     */
    G4Mag_SpinEqRhs( G4MagneticField* MagField );

    /**
     * Default Destructor.
     */
    ~G4Mag_SpinEqRhs() override = default;

    /**
     * Sets the charge momentum mass value.
     */
    void SetChargeMomentumMass(G4ChargeState particleCharge,
                               G4double MomentumXc,
                               G4double mass) override; 

    /**
     * Calculates the value of the derivative, given the value of the field.
     *  @param[in] y Coefficients array.
     *  @param[in] B Field value.
     *  @param[out] dydx Derivatives array.
     */
    void EvaluateRhsGivenB( const G4double y[],
                            const G4double B[3],
                                  G4double dydx[] ) const override;

    /**
     * Setter and getter for the magnetic anomaly.
     */
    inline void SetAnomaly(G4double a) { anomaly = a; }
    inline G4double GetAnomaly() const { return anomaly; }

    /**
     * Returns the equation of motion type ID, i.e. "kEqMagneticWithSpin".
     */
    inline G4EquationType GetEquationType() const override { return kEqMagneticWithSpin; }

  private:

    G4double charge=0.0, mass=0.0, magMoment=0.0, spin=0.0;
    G4double omegac=0.0, anomaly=0.0011659208;
    G4double beta=0.0, gamma=0.0;
};

#endif
