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GeneralDecayMatrixElement.h
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GeneralDecayMatrixElement.h
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// -*- C++ -*-
//
// GeneralDecayMatrixElement.h is a part of Herwig - A multi-purpose Monte Carlo event generator
// Copyright (C) 2002-2017 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_GeneralDecayMatrixElement_H
#define HERWIG_GeneralDecayMatrixElement_H
//
// This is the declaration of the GeneralDecayMatrixElement class.
#include "DecayMatrixElement.h"
#include "GeneralDecayMatrixElement.fh"
namespace Herwig {
using namespace ThePEG;
/** \ingroup Helicity
* \author Peter Richardson
*
* Implementation of the complex matrix element for a decay.
* An arbitary number of external particles are supported.
*
* @see RhoDMatrix
* @see ProductionMatrixElement
* @see DecayVertex
*/
class GeneralDecayMatrixElement: public DecayMatrixElement {
public:
/** @name Standard constructors and destructors. */
//@{
/**
* Default constructor.
*/
GeneralDecayMatrixElement() : DecayMatrixElement(999) {}
/**
* Constructor for two body decay.
* @param spinin \f$2S+1\f$ for the decaying particle
* @param outspin1 \f$2S+1\f$ for the first decay product.
* @param outspin2 \f$2S+1\f$ for the second decay product.
*/
GeneralDecayMatrixElement(PDT::Spin spinin,
PDT::Spin outspin1,PDT::Spin outspin2)
: DecayMatrixElement(2,spinin) {
outspin().push_back(outspin1);
outspin().push_back(outspin2);
setMESize();
}
/**
* Constructor for three body decay.
* @param spinin \f$2S+1\f$ for the decaying particle
* @param outspin1 \f$2S+1\f$ for the first decay product.
* @param outspin2 \f$2S+1\f$ for the second decay product.
* @param outspin3 \f$2S+1\f$ for the third decay product.
*/
GeneralDecayMatrixElement(PDT::Spin spinin,PDT::Spin outspin1,
PDT::Spin outspin2,PDT::Spin outspin3)
: DecayMatrixElement(3,spinin) {
outspin().push_back(outspin1);
outspin().push_back(outspin2);
outspin().push_back(outspin3);
setMESize();
}
/**
* Constructor for four body decay.
* @param spinin \f$2S+1\f$ for the decaying particle
* @param outspin1 \f$2S+1\f$ for the first decay product.
* @param outspin2 \f$2S+1\f$ for the second decay product.
* @param outspin3 \f$2S+1\f$ for the third decay product.
* @param outspin4 \f$2S+1\f$ for the fourth decay product.
*/
GeneralDecayMatrixElement(PDT::Spin spinin,PDT::Spin outspin1,PDT::Spin outspin2,
PDT::Spin outspin3,PDT::Spin outspin4)
: DecayMatrixElement(4,spinin) {
outspin().push_back(outspin1);
outspin().push_back(outspin2);
outspin().push_back(outspin3);
outspin().push_back(outspin4);
setMESize();
}
/**
* Constructor for five body decay.
* @param spinin \f$2S+1\f$ for the decaying particle
* @param outspin1 \f$2S+1\f$ for the first decay product.
* @param outspin2 \f$2S+1\f$ for the second decay product.
* @param outspin3 \f$2S+1\f$ for the third decay product.
* @param outspin4 \f$2S+1\f$ for the fourth decay product.
* @param outspin5 \f$2S+1\f$ for the fifth decay product.
*/
GeneralDecayMatrixElement(PDT::Spin spinin,PDT::Spin outspin1,PDT::Spin outspin2,
PDT::Spin outspin3,PDT::Spin outspin4,PDT::Spin outspin5)
: DecayMatrixElement(5,spinin) {
outspin().push_back(outspin1);
outspin().push_back(outspin2);
outspin().push_back(outspin3);
outspin().push_back(outspin4);
outspin().push_back(outspin5);
setMESize();
}
/**
* Constructor for six body decay.
* @param spinin \f$2S+1\f$ for the decaying particle
* @param outspin1 \f$2S+1\f$ for the first decay product.
* @param outspin2 \f$2S+1\f$ for the second decay product.
* @param outspin3 \f$2S+1\f$ for the third decay product.
* @param outspin4 \f$2S+1\f$ for the fourth decay product.
* @param outspin5 \f$2S+1\f$ for the fifth decay product.
* @param outspin6 \f$2S+1\f$ for the sixth decay product.
*/
GeneralDecayMatrixElement(PDT::Spin spinin,PDT::Spin outspin1,PDT::Spin outspin2,
PDT::Spin outspin3,PDT::Spin outspin4,PDT::Spin outspin5,
PDT::Spin outspin6)
: DecayMatrixElement(6,spinin) {
outspin().push_back(outspin1);
outspin().push_back(outspin2);
outspin().push_back(outspin3);
outspin().push_back(outspin4);
outspin().push_back(outspin5);
outspin().push_back(outspin6);
setMESize();
}
/**
* Constructor for arbitary body decay.
* @param spinin \f$2S+1\f$ for the decaying particle
* @param spinout \f$2S+1\f$ for the decay products.
*/
GeneralDecayMatrixElement(PDT::Spin spinin,vector<PDT::Spin> spinout)
: DecayMatrixElement(spinout.size(),spinin) {
outspin() = spinout;
setMESize();
}
/**
* Constructor for arbitary body decay.
* @param extspin \f$2S+1\f$ external particles.
*/
GeneralDecayMatrixElement(vector<PDT::Spin> extspin)
: DecayMatrixElement(int(extspin.size())-1,extspin[0]) {
outspin() = vector<PDT::Spin>(extspin.begin()+1,extspin.end());
setMESize();
}
//@}
public:
/**
* Spin Density matrices
*/
//@{
/**
* Calculate the decay matrix for this decay.
* @param rhoout The \f$D\f$ matrix for this decay.
*/
RhoDMatrix calculateDMatrix(const vector<RhoDMatrix> & rhoout) const;
/**
* Calculate the \f$\rho\f$ matrix for a given outgoing particle.
* @param ipart The outgoing particle the \f$\rho\f$ matrix is needed for
* @param rhoin The \f$\rho\f$ matrix for the decaying particle.
* @param rhoout he \f$D\f$ matrices for the other decay products.
*/
RhoDMatrix calculateRhoMatrix(int ipart,const RhoDMatrix & rhoin,
const vector<RhoDMatrix> & rhoout) const;
/**
* Contract the matrix element with the \f$\rho\f$ matrix of the
* incoming particle. The spins of the decay products are summed over.
* @param rhoin The \f$\rho\f$ matrix for the decaying particle.
*/
Complex contract(const RhoDMatrix & rhoin) const;
/**
* Contract the matrix element with the \f$\rho\f$ matrix of the
* incoming particle. The spins of the decay products are summed over.
* @param con The conjugate matrix elemetn for the contraction
* @param rhoin The \f$\rho\f$ matrix for the decaying particle.
*/
Complex contract(const GeneralDecayMatrixElement & con,
const RhoDMatrix & rhoin);
//@}
public:
/**
* Access to the individual helicity components.
*/
//@{
/**
* Get the helicity components for a two body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
*/
Complex operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2) const {
unsigned int iloc = inhel*constants_[1]+
outhel1*constants_[2]+outhel2*constants_[3];
assert(outspin().size()==2&&iloc<matrixElement_.size());
return matrixElement_[iloc];
}
/**
* Set the helicity components for a two body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
*/
Complex & operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2) {
unsigned int iloc = inhel*constants_[1]+
outhel1*constants_[2]+outhel2*constants_[3];
assert(outspin().size()==2&&iloc<matrixElement_.size());
return matrixElement_[iloc];
}
/**
* Get the helicity components for a three body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
* @param outhel3 The helicity of the third decay product.
*/
Complex operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2,unsigned int outhel3) const {
unsigned int iloc = inhel*constants_[1]+outhel1*constants_[2]+
outhel2*constants_[3]+outhel3*constants_[4];
assert(outspin().size()==3&&iloc<matrixElement_.size());
return matrixElement_[iloc];
}
/**
* Set the helicity components for a three body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
* @param outhel3 The helicity of the third decay product.
*/
Complex & operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2,unsigned int outhel3) {
unsigned int iloc = inhel*constants_[1]+outhel1*constants_[2]+
outhel2*constants_[3]+outhel3*constants_[4];
assert(outspin().size()==3&&iloc<matrixElement_.size());
return matrixElement_[iloc];
}
/**
* Get the helicity components for a four body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
* @param outhel3 The helicity of the third decay product.
* @param outhel4 The helicity of the fourth decay product.
*/
Complex operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2,unsigned int outhel3,
unsigned int outhel4) const {
vector<unsigned int> itemp(5);
itemp[0]=inhel ; itemp[1]=outhel1;
itemp[2]=outhel2; itemp[3]=outhel3;
itemp[4]=outhel4 ;
return (*this)(itemp);
}
/**
* Set the helicity components for a four body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
* @param outhel3 The helicity of the third decay product.
* @param outhel4 The helicity of the fourth decay product.
*/
Complex & operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2,unsigned int outhel3,
unsigned int outhel4) {
vector<unsigned int> itemp(5);
itemp[0]=inhel ; itemp[1]=outhel1;
itemp[2]=outhel2; itemp[3]=outhel3;
itemp[4]=outhel4;
return (*this)(itemp);
}
/**
* Get the helicity components for a five body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
* @param outhel3 The helicity of the third decay product.
* @param outhel4 The helicity of the fourth decay product.
* @param outhel5 The helicity of the fifth decay product.
*/
Complex operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2,unsigned int outhel3,
unsigned int outhel4,unsigned int outhel5) const {
vector<unsigned int> itemp(6);
itemp[0]=inhel ; itemp[1]=outhel1;
itemp[2]=outhel2; itemp[3]=outhel3;
itemp[4]=outhel4 ;itemp[5]=outhel5;
return (*this)(itemp);
}
/**
* Set the helicity components for a five body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
* @param outhel3 The helicity of the third decay product.
* @param outhel4 The helicity of the fourth decay product.
* @param outhel5 The helicity of the fifth decay product.
*/
Complex & operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2,unsigned int outhel3,
unsigned int outhel4,unsigned int outhel5) {
vector<unsigned int> itemp(6);
itemp[0]=inhel ; itemp[1]=outhel1;
itemp[2]=outhel2; itemp[3]=outhel3;
itemp[4]=outhel4; itemp[5]=outhel5;
return (*this)(itemp);
}
/**
* Get the helicity components for a six body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
* @param outhel3 The helicity of the third decay product.
* @param outhel4 The helicity of the fourth decay product.
* @param outhel5 The helicity of the fifth decay product.
* @param outhel6 The helicity of the sixth decay product.
*/
Complex operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2,unsigned int outhel3,
unsigned int outhel4,unsigned int outhel5,
unsigned int outhel6) const {
vector<unsigned int> itemp(7);
itemp[0]=inhel ; itemp[1]=outhel1;
itemp[2]=outhel2; itemp[3]=outhel3;
itemp[4]=outhel4 ;itemp[5]=outhel5;
itemp[6]=outhel6;
return (*this)(itemp);
}
/**
* Set the helicity components for a six body decay
* @param inhel The helicity of the decaying particle.
* @param outhel1 The helicity of the first decay product.
* @param outhel2 The helicity of the second decay product.
* @param outhel3 The helicity of the third decay product.
* @param outhel4 The helicity of the fourth decay product.
* @param outhel5 The helicity of the fifth decay product.
* @param outhel6 The helicity of the sixth decay product.
*/
Complex & operator () (unsigned int inhel,unsigned int outhel1,
unsigned int outhel2,unsigned int outhel3,
unsigned int outhel4,unsigned int outhel5,
unsigned int outhel6) {
vector<unsigned int> itemp(7);
itemp[0]=inhel ; itemp[1]=outhel1;
itemp[2]=outhel2; itemp[3]=outhel3;
itemp[4]=outhel4; itemp[5]=outhel5;
itemp[6]=outhel6;
return (*this)(itemp);
}
/**
* Get the helicity components for an \f$n\f$-body decay.
* @param in The helicities of the external particles.
*/
Complex operator () (const vector<unsigned int> & in) const {
assert(in.size()==outspin().size()+1);
// contribution for the incoming particle
unsigned int iloc(in[0]*constants_[1]);
// contributions for the outgoing particles
for(unsigned int ix=1;ix<in.size();++ix){iloc+=in[ix]*constants_[ix+1];}
assert(iloc<matrixElement_.size());
return matrixElement_[iloc];
}
/**
* Set the helicity components for an \f$n\f$-body decay.
* @param in The helicities of the external particles.
*/
Complex & operator () (const vector<unsigned int> & in) {
assert(in.size()==outspin().size()+1);
// contribution for the incoming particle
unsigned int iloc(in[0]*constants_[1]);
// contributions for the outgoing particles
for(unsigned int ix=1;ix<in.size();++ix){iloc+=in[ix]*constants_[ix+1];}
assert(iloc<matrixElement_.size());
return matrixElement_[iloc];
}
//@}
/**
* Member to zero all the elements for the matrix element
*/
void zero() {
for(unsigned int ix=0;ix<matrixElement_.size();++ix)
matrixElement_[ix]=0.;
}
/**
* Set the size of the vector containing the matrix element.
*/
void setMESize() {
int isize = inspin();
for(unsigned int ix=0;ix<outspin().size();++ix) isize*=outspin()[ix];
matrixElement_.resize(isize,0.);
// set up the constants for the mapping of helicity to vector index
constants_.resize(outspin().size()+2);
int temp=1;
for(unsigned int ix=outspin().size();ix>0;--ix) {
temp*=outspin()[ix-1];constants_[ix]=temp;
}
temp *= inspin();
constants_[0]=temp;
constants_[outspin().size()+1]=1;
}
private:
/**
* Storage of the matrix element, a vector is better for memory usage.
*/
mutable vector<Complex> matrixElement_;
/**
* Constants needed to map the index of the vector to a helicity structure.
*/
mutable vector<unsigned int> constants_;
};
}
#endif /* HERWIG_GeneralDecayMatrixElement_H */

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