Herwig/MatrixElement/ProductionMatrixElement.h

0001 // -*- C++ -*-
0002 //
0003 // ProductionMatrixElement.h is a part of Herwig - A multi-purpose Monte Carlo event generator
0004 // Copyright (C) 2002-2019 The Herwig Collaboration
0005 //
0006 // Herwig is licenced under version 3 of the GPL, see COPYING for details.
0007 // Please respect the MCnet academic guidelines, see GUIDELINES for details.
0008 //
0009 #ifndef HERWIG_ProductionMatrixElement_H
0010 #define HERWIG_ProductionMatrixElement_H
0011 //
0012 // This is the declaration of the ProductionMatrixElement class.
0013
0014 #include <ThePEG/EventRecord/RhoDMatrix.h>
0015
0016 namespace Herwig {
0017
0018
0019 using namespace ThePEG;
0020
0021 /** \ingroup Helicity
0022  *
0023  *  The storage of the helicity amplitude expression for the matrix element
0024  *  of a hard process. Two incoming particles and an arbitary number of
0025  *  external particles are supported.
0026  *
0027  *  @see DecayMatrixElement
0028  *  @see RhoDMatrix
0029  *  @see HardVertex
0030  *
0031  *  \author Peter Richardson
0032  */
0033
0034 class ProductionMatrixElement {
0035
0036 public:
0037
0038   /** @name Standard constructors and destructors. */
0039   //@{
0040   /**
0041    * Constructor for 2-1 scattering.
0042    * @param in1 \f$2S+1\f$ for the first incoming particle.
0043    * @param in2 \f$2S+1\f$ for the second incoming particle.
0044    * @param out \f$2S+1\f$ for the outgoing particle.
0045    */
0046   ProductionMatrixElement(PDT::Spin in1,PDT::Spin in2,PDT::Spin out);
0047
0048   /**
0049    * Constructor for 2-2 scattering.
0050    * @param in1 \f$2S+1\f$ for the first incoming particle.
0051    * @param in2 \f$2S+1\f$ for the second incoming particle.
0052    * @param out1 \f$2S+1\f$ for the first outgoing particle.
0053    * @param out2 \f$2S+1\f$ for the second outgoing particle.
0054    */
0055   ProductionMatrixElement(PDT::Spin in1,PDT::Spin in2,PDT::Spin out1,
0056               PDT::Spin out2);
0057
0058   /**
0059    * Constructor for 2-3 scattering.
0060    * @param in1 \f$2S+1\f$ for the first incoming particle.
0061    * @param in2 \f$2S+1\f$ for the second incoming particle.
0062    * @param out1 \f$2S+1\f$ for the first outgoing particle.
0063    * @param out2 \f$2S+1\f$ for the second outgoing particle.
0064    * @param out3 \f$2S+1\f$ for the third outgoing particle.
0065    */
0066   ProductionMatrixElement(PDT::Spin in1,PDT::Spin in2,PDT::Spin out1,
0067               PDT::Spin out2,PDT::Spin out3);
0068
0069   /**
0070    * Constructor for 2-4 scattering.
0071    * @param in1 \f$2S+1\f$ for the first incoming particle.
0072    * @param in2 \f$2S+1\f$ for the second incoming particle.
0073    * @param out1 \f$2S+1\f$ for the first outgoing particle.
0074    * @param out2 \f$2S+1\f$ for the second outgoing particle.
0075    * @param out3 \f$2S+1\f$ for the third outgoing particle.
0076    * @param out4 \f$2S+1\f$ for the fourth outgoing particle.
0077    */
0078   ProductionMatrixElement(PDT::Spin in1,PDT::Spin in2,PDT::Spin out1,
0079               PDT::Spin out2,PDT::Spin out3, PDT::Spin out4);
0080
0081   /**
0082    * Constructor for 2-5 scattering.
0083    * @param in1 \f$2S+1\f$ for the first incoming particle.
0084    * @param in2 \f$2S+1\f$ for the second incoming particle.
0085    * @param out1 \f$2S+1\f$ for the first outgoing particle.
0086    * @param out2 \f$2S+1\f$ for the second outgoing particle.
0087    * @param out3 \f$2S+1\f$ for the third outgoing particle.
0088    * @param out4 \f$2S+1\f$ for the fourth outgoing particle.
0089    * @param out5 \f$2S+1\f$ for the fifth outgoing particle.
0090    */
0091   ProductionMatrixElement(PDT::Spin in1,PDT::Spin in2,PDT::Spin out1,
0092               PDT::Spin out2,PDT::Spin out3, PDT::Spin out4,
0093               PDT::Spin out5);
0094
0095   /**
0096    * Constructor for 2-6 scattering.
0097    * @param in1 \f$2S+1\f$ for the first incoming particle.
0098    * @param in2 \f$2S+1\f$ for the second incoming particle.
0099    * @param out1 \f$2S+1\f$ for the first outgoing particle.
0100    * @param out2 \f$2S+1\f$ for the second outgoing particle.
0101    * @param out3 \f$2S+1\f$ for the third outgoing particle.
0102    * @param out4 \f$2S+1\f$ for the fourth outgoing particle.
0103    * @param out5 \f$2S+1\f$ for the fifth outgoing particle.
0104    * @param out6 \f$2S+1\f$ for the sixth outgoing particle.
0105    */
0106   ProductionMatrixElement(PDT::Spin in1,PDT::Spin in2,PDT::Spin out1,
0107               PDT::Spin out2,PDT::Spin out3, PDT::Spin out4,
0108               PDT::Spin out5, PDT::Spin out6);
0109
0110   /**
0111    * Constructor for 2-n scattering.
0112    * @param in1 \f$2S+1\f$ for the first incoming particle.
0113    * @param in2 \f$2S+1\f$ for the second incoming particle.
0114    * @param out A vector containing \f$2S+1\f$ for the outgoing particles.
0115    */
0116   ProductionMatrixElement(PDT::Spin in1,PDT::Spin in2,vector<PDT::Spin> out);
0117
0118   /**
0119    * Default constructor.
0120    */
0121   ProductionMatrixElement() : _nout(0) {}
0122   //@}
0123
0124 public:
0125
0126   /** @name Access to the spins of the particles. */
0127   //@{
0128   /**
0129    * Get the spins of the incoming particles particle
0130    * @return A vector containing \f$2S+1\f$ for the two incoming particles.
0131    */
0132   vector<PDT::Spin> inspin() {return _inspin;}
0133
0134   /**
0135    * Get the spins of the outgoing particles.
0136    * @return A vector containing \f$2S+1\f$ for the outgoing particles.
0137    */
0138   vector<PDT::Spin> outspin() {return _outspin;}
0139   //@}
0140
0141 public:
0142
0143   /** @name Access to the individual helicity components. */
0144   //@{
0145   /**
0146    * Access the helicity components for a 2-1 scattering. This method supplies
0147    * the component but does not allow it to be changed.
0148    * @param in1 The helicity of the first incoming particle.
0149    * @param in2 The helicity of the second incoming particle.
0150    * @param out The helicity of the outgoing particle.
0151    * @return The matrix element for the given helicities.
0152    */
0153   Complex   operator () (unsigned int in1,unsigned int in2,
0154              unsigned int out) const;
0155
0156   /**
0157    * Access the helicity components for a 2-1 scattering. This method supplies
0158    * the component and allows it to be changed.
0159    * @param in1 The helicity of the first incoming particle.
0160    * @param in2 The helicity of the second incoming particle.
0161    * @param out The helicity of the outgoing particle.
0162    * @return The matrix element for the given helicities.
0163    */
0164   Complex & operator () (unsigned int in1,unsigned int in2,
0165              unsigned int out);
0166
0167   /**
0168    * Access the helicity components for a 2-2 scattering. This method supplies
0169    * the component but does not allow it to be changed.
0170    * @param in1 The helicity of the first incoming particle.
0171    * @param in2 The helicity of the second incoming particle.
0172    * @param out1 The helicity of the first outgoing particle.
0173    * @param out2 The helicity of the second outgoing particle.
0174    * @return The matrix element for the given helicities.
0175    */
0176   Complex   operator () (unsigned int in1,unsigned int in2,
0177              unsigned int out1,unsigned int out2) const;
0178
0179   /**
0180    * Access the helicity components for a 2-2 scattering. This method supplies
0181    * the component and allows it to be changed.
0182    * @param in1 The helicity of the first incoming particle.
0183    * @param in2 The helicity of the second incoming particle.
0184    * @param out1 The helicity of the first outgoing particle.
0185    * @param out2 The helicity of the second outgoing particle.
0186    * @return The matrix element for the given helicities.
0187    */
0188   Complex & operator () (unsigned int in1,unsigned int in2,
0189              unsigned int out1,unsigned int out2);
0190
0191   /**
0192    * Access the helicity components for a 2-3 scattering. This method supplies
0193    * the component but does not allow it to be changed.
0194    * @param in1 The helicity of the first incoming particle.
0195    * @param in2 The helicity of the second incoming particle.
0196    * @param out1 The helicity of the first outgoing particle.
0197    * @param out2 The helicity of the second outgoing particle.
0198    * @param out3 The helicity of the third outgoing particle.
0199    * @return The matrix element for the given helicities.
0200    */
0201   Complex   operator () (unsigned int in1,unsigned int in2,
0202              unsigned int out1,unsigned int out2,
0203              unsigned int out3) const;
0204
0205   /**
0206    * Access the helicity components for a 2-3 scattering. This method supplies
0207    * the component and allows it to be changed.
0208    * @param in1 The helicity of the first incoming particle.
0209    * @param in2 The helicity of the second incoming particle.
0210    * @param out1 The helicity of the first outgoing particle.
0211    * @param out2 The helicity of the second outgoing particle.
0212    * @param out3 The helicity of the third outgoing particle.
0213    * @return The matrix element for the given helicities.
0214    */
0215   Complex & operator () (unsigned int in1,unsigned int in2,
0216              unsigned int out1,unsigned int out2,
0217              unsigned int out3);
0218
0219   /**
0220    * Access the helicity components for a 2-4 scattering.  This method supplies
0221    * the component but does not allow it to be changed.
0222    * @param in1 The helicity of the first incoming particle.
0223    * @param in2 The helicity of the second incoming particle.
0224    * @param out1 The helicity of the first outgoing particle.
0225    * @param out2 The helicity of the second outgoing particle.
0226    * @param out3 The helicity of the third outgoing particle.
0227    * @param out4 The helicity of the fourth outgoing particle.
0228    * @return The matrix element for the given helicities.
0229    */
0230   Complex   operator () (unsigned int in1,unsigned int in2,
0231              unsigned int out1,unsigned int out2,
0232              unsigned int out3,unsigned int out4) const;
0233
0234   /**
0235    * Access the helicity components for a 2-4 scattering. This method supplies
0236    * the component and allows it to be changed.
0237    * @param in1 The helicity of the first incoming particle.
0238    * @param in2 The helicity of the second incoming particle.
0239    * @param out1 The helicity of the first outgoing particle.
0240    * @param out2 The helicity of the second outgoing particle.
0241    * @param out3 The helicity of the third outgoing particle.
0242    * @param out4 The helicity of the fourth outgoing particle.
0243    * @return The matrix element for the given helicities.
0244    */
0245   Complex & operator () (unsigned int in1,unsigned int in2,
0246              unsigned int out1,unsigned int out2,
0247              unsigned int out3, unsigned int out4);
0248
0249   /**
0250    * Access the helicity components for a 2-5 scattering. This method supplies
0251    * the component but does not allow it to be changed.
0252    * @param in1 The helicity of the first incoming particle.
0253    * @param in2 The helicity of the second incoming particle.
0254    * @param out1 The helicity of the first outgoing particle.
0255    * @param out2 The helicity of the second outgoing particle.
0256    * @param out3 The helicity of the third outgoing particle.
0257    * @param out4 The helicity of the fourth outgoing particle.
0258    * @param out5 The helicity of the fifth outgoing particle.
0259    * @return The matrix element for the given helicities.
0260    */
0261   Complex   operator () (unsigned int in1,unsigned int in2,
0262              unsigned int out1,unsigned int out2,
0263              unsigned int out3,unsigned int out4,
0264              unsigned int out5) const;
0265
0266   /**
0267    * Access the helicity components for a 2-5 scattering. This method supplies
0268    * the component and allows it to be changed.
0269    * @param in1 The helicity of the first incoming particle.
0270    * @param in2 The helicity of the second incoming particle.
0271    * @param out1 The helicity of the first outgoing particle.
0272    * @param out2 The helicity of the second outgoing particle.
0273    * @param out3 The helicity of the third outgoing particle.
0274    * @param out4 The helicity of the fourth outgoing particle.
0275    * @param out5 The helicity of the fifth outgoing particle.
0276    * @return The matrix element for the given helicities.
0277    */
0278   Complex & operator () (unsigned int in1,unsigned int in2,
0279              unsigned int out1,unsigned int out2,
0280              unsigned int out3, unsigned int out4,
0281              unsigned int out5);
0282
0283   /**
0284    * Access the helicity components for a 2-6 scattering. This method supplies
0285    * the component but does not allow it to be changed.
0286    * @param in1 The helicity of the first incoming particle.
0287    * @param in2 The helicity of the second incoming particle.
0288    * @param out1 The helicity of the first outgoing particle.
0289    * @param out2 The helicity of the second outgoing particle.
0290    * @param out3 The helicity of the third outgoing particle.
0291    * @param out4 The helicity of the fourth outgoing particle.
0292    * @param out5 The helicity of the fifth outgoing particle.
0293    * @param out6 The helicity of the sixth outgoing particle.
0294    * @return The matrix element for the given helicities.
0295    */
0296   Complex   operator () (unsigned int in1,unsigned int in2,
0297              unsigned int out1,unsigned int out2,
0298              unsigned int out3,unsigned int out4,
0299              unsigned int out5,unsigned int out6) const;
0300
0301   /**
0302    * Access the helicity components for a 2-6 scattering. This method supplies
0303    * the component and allows it to be changed.
0304    * @param in1 The helicity of the first incoming particle.
0305    * @param in2 The helicity of the second incoming particle.
0306    * @param out1 The helicity of the first outgoing particle.
0307    * @param out2 The helicity of the second outgoing particle.
0308    * @param out3 The helicity of the third outgoing particle.
0309    * @param out4 The helicity of the fourth outgoing particle.
0310    * @param out5 The helicity of the fifth outgoing particle.
0311    * @param out6 The helicity of the sixth outgoing particle.
0312    * @return The matrix element for the given helicities.
0313    */
0314   Complex & operator () (unsigned int in1,unsigned int in2,
0315              unsigned int out1,unsigned int out2,
0316              unsigned int out3, unsigned int out4,
0317              unsigned int out5, unsigned int out6);
0318
0319   /**
0320    * Access the helicity components for a 2-n scattering. This method supplies
0321    * the component but does not allow it to be changed.
0322    * @param hel The helicities of the incoming and outgoing particles
0323    * @return The matrix element for the given helicities.
0324    */
0325   Complex   operator () (vector<unsigned int> hel) const;
0326
0327   /**
0328    * Access the helicity components for a 2-n scattering. This method supplies
0329    * the component and allows it to be changed.
0330    * @param hel The helicities of the incoming and outgoing particles
0331    * @return The matrix element for the given helicities.
0332    */
0333   Complex & operator () (vector<unsigned int> hel);
0334   //@}
0335
0336 public:
0337
0338   /**
0339    * Calculate the decay matrix for an incoming particle.
0340    */
0341   RhoDMatrix calculateDMatrix(int,const RhoDMatrix &,
0342                   const vector<RhoDMatrix> &) const;
0343
0344   /**
0345    * Calculate the rho matrix for a given outgoing particle.
0346    */
0347   RhoDMatrix calculateRhoMatrix(int,const RhoDMatrix &,
0348                                 const RhoDMatrix &,
0349                 const vector<RhoDMatrix> &) const;
0350
0351   /**
0352    *  Compute the spin averaged matrix element
0353    */
0354   double average() const;
0355
0356   /**
0357    *  Compute the spin average matrix element
0358    */
0359   double average(const RhoDMatrix & in1,
0360          const RhoDMatrix & in2) const;
0361
0362   /**
0363    *  Compute the spin average matrix element
0364    */
0365   Complex average(const ProductionMatrixElement & me2,
0366           const RhoDMatrix & in1,
0367           const RhoDMatrix & in2) const;
0368
0369 public:
0370
0371   /**
0372    * Reset the matrix element.
0373    */
0374   void reset(const ProductionMatrixElement & x) const;
0375
0376   /**
0377    * Standard Init function used to initialize the interfaces.
0378    */
0379   static void Init();
0380
0381 private:
0382
0383   /**
0384    * Set the size of the vector containing the matrix element.
0385    */
0386   void setMESize();
0387
0388 private:
0389
0390   /**
0391    * Number of outgoing particles.
0392    */
0393   mutable unsigned int _nout;
0394
0395   /**
0396    * Spin of the incoming particles as 2s+1.
0397    */
0398   mutable vector<PDT::Spin> _inspin;
0399
0400   /**
0401    * Spins of the outgoing particles.
0402    */
0403   mutable vector<PDT::Spin> _outspin;
0404
0405   /**
0406    * Storage of the matrix element, a vector is better for memory usage.
0407    */
0408   mutable vector<Complex> _matrixelement;
0409
0410   /**
0411    * Constants needed to map the index of the vector to a helicity structure.
0412    */
0413   mutable vector<int> _constants;
0414
0415 };
0416
0417 }
0418
0419 #endif /* HERWIG_ProductionMatrixElement_H */