SpinCorrelationTensor.h

// -*- C++ -*-
//
// SpinCorrelationTensor.h is a part of Herwig - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2019 The Herwig Collaboration
//
// Herwig is licenced under version 3 of the GPL, see COPYING for details.
// Please respect the MCnet academic guidelines, see GUIDELINES for details.
//
#ifndef HERWIG_SpinCorrelationTensor_H
#define HERWIG_SpinCorrelationTensor_H
 
#include "ThePEG/Config/Unitsystem.h"
 
namespace Herwig {
 
using namespace ThePEG;
 
class SpinCorrelationTensor {
 
  double theDiagonal;
 
  Lorentz5Momentum theMomentum;
 
  Energy2 theScale;
 
public:
 
  SpinCorrelationTensor(double diag,
                        const Lorentz5Momentum& p,
                        Energy2 sc) 
    : theDiagonal(diag), theMomentum(p), theScale(sc) {}
 
public:
 
  double diagonal() const { return theDiagonal; }
 
  const Lorentz5Momentum& momentum() const { return theMomentum; }
 
  Energy2 scale() const { return theScale; }
 
public:
 
  Complex matrixElement(const LorentzVector<Complex>& left,
                        const LorentzVector<Complex>& right) const {
    return
      left.dot(momentum())*right.dot(momentum())/scale();
  }
 
};
 
}
 
#endif // HERWIG_SpinCorrelationTensor_H