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 // -*- C++ -*-
 #ifndef HERWIG_MEMinBias_H
 #define HERWIG_MEMinBias_H
 //
 // This is the declaration of the MEMinBias class.
 //
 
 #include "Herwig/MatrixElement/HwMEBase.h"
 #include "Herwig/Shower/UEBase.h"
 
 namespace Herwig {
 
 using namespace ThePEG;
 
 /**
  * The MEMinBias class provides a simple colour singlet exchange matrix element
  * to be used in the soft component of the multiple scattering model of the 
  * underlying event
  *
  * @see \ref MEMinBiasInterfaces "The interfaces"
  * defined for MEMinBias.
  */
 class MEMinBias: public HwMEBase {
 
 public:
 
   /**
    * The default constructor.
    */
   MEMinBias() : csNorm_(1.), Scale_(2.*GeV) {}
 
 public:
 
   /** @name Virtual functions required by the MEBase class. */
   //@{
   /**
    * Return the order in \f$\alpha_S\f$ in which this matrix
    * element is given.
    */
   virtual unsigned int orderInAlphaS() const;
 
   /**
    * Return the order in \f$\alpha_{EW}\f$ in which this matrix
    * element is given.
    */
   virtual unsigned int orderInAlphaEW() const;
 
   /**
    * The matrix element for the kinematical configuration
    * previously provided by the last call to setKinematics(), suitably
    * scaled by sHat() to give a dimension-less number.
    * @return the matrix element scaled with sHat() to give a
    * dimensionless number.
    */
   virtual double me2() const;
 
   /**
    * Correction weight to reweight the cross section to the inelastic cross
    * section subtracted by the diffractive cross section.
    */
   double correctionweight() const;
   
   /**
    * Return the scale associated with the last set phase space point.
    */
   virtual Energy2 scale() const;
 
   /**
    * Set the typed and momenta of the incoming and outgoing partons to
    * be used in subsequent calls to me() and colourGeometries()
    * according to the associated XComb object. If the function is
    * overridden in a sub class the new function must call the base
    * class one first.
    */
   virtual void setKinematics();
 
   /**
    * The number of internal degrees of freedom used in the matrix
    * element.
    */
   virtual int nDim() const;
 
   /**
    * Generate internal degrees of freedom given nDim() uniform
    * random numbers in the interval \f$ ]0,1[ \f$. To help the phase space
    * generator, the dSigHatDR should be a smooth function of these
    * numbers, although this is not strictly necessary.
    * @param r a pointer to the first of nDim() consecutive random numbers.
    * @return true if the generation succeeded, otherwise false.
    */
   virtual bool generateKinematics(const double * r);
 
   /**
    * Return the matrix element squared differential in the variables
    * given by the last call to generateKinematics().
    */
   virtual CrossSection dSigHatDR() const;
 
   /**
    * Add all possible diagrams with the add() function.
    */
   virtual void getDiagrams() const;
 
   /**
    * Get diagram selector. With the information previously supplied with the
    * setKinematics method, a derived class may optionally
    * override this method to weight the given diagrams with their
    * (although certainly not physical) relative probabilities.
    * @param dv the diagrams to be weighted.
    * @return a Selector relating the given diagrams to their weights.
    */
   virtual Selector<DiagramIndex> diagrams(const DiagramVector & dv) const;
 
   /**
    * Return a Selector with possible colour geometries for the selected
    * diagram weighted by their relative probabilities.
    * @param diag the diagram chosen.
    * @return the possible colour geometries weighted by their
    * relative probabilities.
    */
   virtual Selector<const ColourLines *>
   colourGeometries(tcDiagPtr diag) 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.
    */
 
 
   /**
    * 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:
 
   /** @name Clone Methods. */
   //@{
   /**
    * Make a simple clone of this object.
    * @return a pointer to the new object.
    */
   virtual IBPtr clone() const;
 
   /** Make a clone of this object, possibly modifying the cloned object
    * to make it sane.
    * @return a pointer to the new object.
    */
   virtual IBPtr fullclone() const;
   //@}
 
 
 // If needed, insert declarations of virtual function defined in the
 // InterfacedBase class here (using ThePEG-interfaced-decl in Emacs).
 
 
 private:
   /**
    * Normalization of the min-bias cross section.
    * Note that the cross section is reweighted in addition to produce the
    * non-diffractive cross section given by the MPIHandler
    * csNorm can be modified to improve the unweighting effiency.  
    */
   double csNorm_;   
 
   /**
    * Scale for the Min Bias matrix element
    */
   Energy Scale_;
 
   /**
    * Allow only valence quark extraction.
    */ 
   bool onlyValQuarks_=true;
 
   /**
    * a MPIHandler to administer the creation of several (semihard) 
    * partonic interactions.
    * Needed to comunicate the non-diffractive cross section.
    */
   UEBasePtr MPIHandler_;
 
   /**
    * The assignment operator is private and must never be called.
    * In fact, it should not even be implemented.
    */
   MEMinBias & operator=(const MEMinBias &) = delete;
 
 };
 
 }
 
 #endif /* HERWIG_MEMinBias_H */

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