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 // -*- C++ -*-
 #ifndef THEPEG_MixedParticleData_H
 #define THEPEG_MixedParticleData_H
 //
 // This is the declaration of the MixedParticleData class.
 //
 
 #include "ParticleData.h"
 #include "MixedParticleData.fh"
 
 namespace ThePEG {
 
 /**
  * The MixedParticleData class is designed to store the 
  * particle data for particles which undergo mixing with their
  * anti-particle, e.g. \f$B^0-\bar{B}^0\f$, \f$B_s^0-\bar{B}_s^0\f$, 
  * \f$D^0-\bar{D}^0\f$.
  *
  *  The key parameters are the mass difference between the heavier 
  *  and lighter states, \f$\Delta m = m_H-m_L\f$, the width difference
  *  \f$\Delta\Gamma = \Gamma_H-\Gamma_L\f$. While the mass difference
  *  is positive by definition the sign of the width difference must be
  *  determined experimentally. It should be noted that because the width
  *  difference is expected to be negative in the Standard Model many
  *  experiment results use the convention 
  *  \f$\Delta\Gamma = \Gamma_L - \Gamma_H\f$ so care should be taken.
  *
  *  In order to be as general as possible we have included the option
  *  of CPT violation, in addition to the violation of CP, in the mixing
  *  in this case the light and heavy eigenstates are given by
  * \f[|M_L\rangle \propto p \sqrt{1-z}|     M^0 \rangle 
  *                    + q \sqrt{1+z}|\bar{M}^0\rangle,\f]
  * \f[|M_H\rangle \propto p \sqrt{1+z}|     M^0 \rangle 
  *                    - q \sqrt{1-z}|\bar{M}^0\rangle,\f]
  *  where \f$p\f$, \f$q\f$ and \f$z\f$ are complex parameters with \f$z=0\f$ if CPT
  *  is conserved.
  *
  *  This gives the time evolution of the states
  * \f[|M^0_{\rm phys}(t)\rangle = (g_+(t)+zg_-(t))|M^0\rangle
  *                                -sqrt{1-z^2}\frac{q}{p}g_-(t)|\bar{M}^0\rangle,\f]
  * \f[\bar{M}^-_{\rm phys}\rangle = (g_+(t)+zg_-(t))|\bar{M}^0\rangle
  *                                -sqrt{1-z^2}\frac{p}{q}g_-(t)|M^0\rangle,\f]
  * for particles initially in a pure particle or antiparticle state
  * where
  * \f[g_\pm(t)=\frac12\left(e^{-im_Ht-\frac12\Gamma_Ht} \pm
  *                       e^{-im_Lt-\frac12\Gamma_Lt}\right).\f]
  * @see \ref MixedParticleDataInterfaces "The interfaces"
  * defined for MixedParticleData.
  */
 class MixedParticleData: public ParticleData {
 
 public:
 
   /**
    * The default constructor.
    */
   MixedParticleData() : ParticleData(), _deltam(0.*GeV), 
             _deltagamma(0.*GeV), _pqmag(1.), _pqphase(0.),
             _pq(1.,0.), _zmag(0.), _zphase(0.), _z(0.), _x(0.), _y(0.),
             _prob(make_pair(1.,0.))
   {}
 
   /** @name The Create methods are special interfaces for ParticleData
       classes. */
   //@{
   /**
    * Create a Particle which is its own anti-particle.
    */
   static PDPtr Create(long newId, string newPDGName);
 
   /**
    * Create a particle - anti particle pair.
    */
   static PDPair Create(long newId, string newPDGName, string newAntiPDGName);
   //@}
 
 public:
 
   /**
    *  Mixing parameters
    */
   //@{
   /**
    *  The mass difference
    */
   Energy deltaM() const {return _deltam;}
 
   /**
    *  The width difference
    */
   Energy deltaGamma() const {return _deltagamma;}
 
   /**
    *  \f$p/q\f$
    */
   Complex pq() const {return _pq;}
 
   /**
    *  \f$z\f$
    */
   Complex z() const {return _z;}
 
   /**
    *  The \f$x\f$ mixing variable
    */
   double x() const {return _x;}
 
   /**
    *  the \f$y\f$ mixing variable
    */
   double y() const {return _y;}
 
   /**
    *  The time-integrated mixing probabilities
    */
   pair<double,double> prob() const {return _prob;}
 
   /**
    *  For a given paricle decide is it undergoes mixing
    *  and generate the lifetime
    */
   pair<bool,Length> generateLifeTime() const;
 
   /**
    *  The amplitudes for the different states
    */
   pair<Complex,Complex> mixingAmplitudes(Length,bool) const;
 
 public:
 
   /** @name Functions used by the persistent I/O system. */
   //@{
   /**
    * Function used to write out object persistently.
    * @param os the persistent output stream written to.
    */
   void persistentOutput(PersistentOStream & os) const;
 
   /**
    * Function used to read in object persistently.
    * @param is the persistent input stream read from.
    * @param version the version number of the object when written.
    */
   void persistentInput(PersistentIStream & is, int version);
   //@}
 
   /**
    * The standard Init function used to initialize the interfaces.
    * Called exactly once for each class by the class description system
    * before the main function starts or
    * when this class is dynamically loaded.
    */
   static void Init();
 
 protected:
 
   /**
    * Protected constructor only to be used by subclasses or by the
    * Create method.
    */
   MixedParticleData(long newId, string newPDGName);
 
   /**
    * ParticleData clone method
    */
   virtual PDPtr pdclone() const;
 
 protected:
 
   /** @name Standard Interfaced functions. */
   //@{
   /**
    * Initialize this object after the setup phase before saving an
    * EventGenerator to disk.
    * @throws InitException if object could not be initialized properly.
    */
   virtual void doinit();
   //@}
 
 private:
 
   /**
    *  Function for the interface to set the mass difference
    */
   void setDeltaM(Energy);
 
   /**
    *  Function for the interface to set the width difference
    */
   void setDeltaGamma(Energy);
 
   /**
    *  Function for the interface to set the magnitude of p/q
    */
   void setPQMagnitude(double);
 
   /**
    *  Function for the interface to set the phase of p/q
    */
   void setPQPhase(double);
 
   /**
    *  Function for the interface to set the magnitude of z
    */
   void setZMagnitude(double);
 
   /**
    *  Function for the interface to set the phase of z
    */
   void setZPhase(double);
 
 private:
 
   /**
    * The static object used to initialize the description of this class.
    * Indicates that this is a concrete class with persistent data.
    */
   static ClassDescription<MixedParticleData> initMixedParticleData;
 
   /**
    * The assignment operator is private and must never be called.
    * In fact, it should not even be implemented.
    */
   MixedParticleData & operator=(const MixedParticleData &) = delete;
 
 private:
 
   /**
    *  Mixing parameters
    */
   //@{
   /**
    *  The mass difference
    */
   Energy _deltam;
 
   /**
    *  The width difference
    */
   Energy _deltagamma;
 
   /**
    *  The magnitude of \f$p/q\f$
    */
   double _pqmag;
 
   /**
    *  The phase of \f$p/q\f$
    */
   double _pqphase;
 
   /**
    *  \f$p/q\f$
    */
   Complex _pq;
 
   /**
    *  The magnitude of \f$z\f$
    */
   double _zmag;
 
   /**
    *  The phase of \f$z\f$
    */
   double _zphase;
 
   /**
    * The \f$z\f$ parameter
    */
   Complex _z;
 
   /**
    *  The \f$x\f$ mixing variable
    */
   double _x;
 
   /**
    *  the \f$y\f$ mixing variable
    */
   double _y;
 
   /**
    *  The time-integrated mixing probabilities
    */
   pair<double,double> _prob;
   //@}
 
 };
 
 }
 
 #include "ThePEG/Utilities/ClassTraits.h"
 
 namespace ThePEG {
 
 /** @cond TRAITSPECIALIZATIONS */
 
 /** This template specialization informs ThePEG about the
  *  base classes of MixedParticleData. */
 template <>
 struct BaseClassTrait<MixedParticleData,1> {
   /** Typedef of the first base class of MixedParticleData. */
   typedef ParticleData NthBase;
 };
 
 /** This template specialization informs ThePEG about the name of
  *  the MixedParticleData class and the shared object where it is defined. */
 template <>
 struct ClassTraits<MixedParticleData>
   : public ClassTraitsBase<MixedParticleData> {
   /** Return a platform-independent class name */
   static string className() { return "ThePEG::MixedParticleData"; }
 };
 
 /** @endcond */
 
 }
 
 #endif /* THEPEG_MixedParticleData_H */

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