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BaryonSimpleFormFactor.cc
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BaryonSimpleFormFactor.cc
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// -*- C++ -*-
//
// This is the implementation of the non-inlined, non-templated member
// functions of the BaryonSimpleFormFactor class.
//
#include "BaryonSimpleFormFactor.h"
#include "ThePEG/Utilities/DescribeClass.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/Interface/Parameter.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
using namespace Herwig;
using namespace ThePEG;
BaryonSimpleFormFactor::BaryonSimpleFormFactor() {
// axial vector coupling in beta decay
_gA=1.25;
// SU(3) breaking paramters
// D/(D+F) ratio
_alphaD=0.6;
// eta_V parameter
_etaV=0.970;
// eta_A parameter
_etaA=1.080;
// SU(3) breaking factors for the electric dipole moment
_rhoE=0.094;
// SU(3) breaking factors for the magnetic dipole moment
_rhoM=0.860;
// the various decay modes handled by the model
addFormFactor(2112,2212,2,2,2,1,1,2);
addFormFactor(3222,3122,2,2,3,2,1,2);
addFormFactor(3112,3122,2,2,3,1,1,2);
addFormFactor(3112,3212,2,2,3,1,1,2);
addFormFactor(3212,3222,2,2,3,2,1,2);
addFormFactor(3312,3322,2,2,3,3,1,2);
addFormFactor(3122,2212,2,2,2,1,3,2);
addFormFactor(3212,2212,2,2,2,1,3,2);
addFormFactor(3112,2112,2,2,1,1,3,2);
addFormFactor(3312,3122,2,2,3,1,3,2);
addFormFactor(3312,3212,2,2,3,1,3,2);
addFormFactor(3322,3222,2,2,3,2,3,2);
// set the inital number of form factors
initialModes(numberOfFactors());
}
void BaryonSimpleFormFactor::doinit() {
BaryonFormFactor::doinit();
_f1.clear();
_f2.clear();
_g1.clear();
_g2.clear();
_f1.resize(numberOfFactors());
_f2.resize(numberOfFactors());
_g1.resize(numberOfFactors());
_g2.resize(numberOfFactors());
// calculate the couplings for the different modes
int id0,id1;
double root23(sqrt(2./3.)),root2(sqrt(2.)),root32(sqrt(3./2.));
for(unsigned int ix=0;ix<numberOfFactors();++ix) {
// get the particle ids for the mode
particleID(ix,id0,id1);
// work out the couplings
// neutron beta decay
if(id0==2112&&id1==2212) {
_f1[ix] = 1. ;
_g1[ix] = _gA;
_f2[ix] = 3.7*_gA-1.0;
_g2[ix] = 0.;
}
// sigma+ to Lambda
else if(id0==3222&&id1==3122) {
_f1[ix] = 0.;
_g1[ix] = _gA*root23*_alphaD;
_f2[ix] = 4.55*_g1[ix]-1.0*_f1[ix];
_g2[ix] = -0.03*_g1[ix];
}
// sigma
else if(id0==3112&&id1==3122) {
_f1[ix] = 0.;
_g1[ix] = _gA*root23*_alphaD;
_f2[ix] = 4.55*_g1[ix]-1.0*_f1[ix];
_g2[ix] = -0.03*_g1[ix];
}
else if(id0==3112&&id1==3212) {
_f1[ix] = root2;
_g1[ix] = _gA*root2*(1.-_alphaD);
_f2[ix] = 4.69*_g1[ix]-_f1[ix];
_g2[ix] = 0.;
}
else if(id0==3212&&id1==3222) {
_f1[ix] = -root2;
_g1[ix] = -_gA*root2*(1.-_alphaD);
_f2[ix] = 4.69*_g1[ix]-_f1[ix];
_g2[ix] = 0.;
}
else if(id0==3312&&id1==3322) {
_f1[ix] = -1.;
_g1[ix] = -_gA*(1.-2.*_alphaD);
_f2[ix] = 5.21*_g1[ix]-_f1[ix];
_g2[ix] = 0.;
}
else if(id0==3122&&id1==2212) {
_f1[ix] = -root32*_etaV;
_g1[ix] = -_gA*root32*_etaA*(1.-2.*_alphaD/3.);
_f2[ix] = 4.05*_rhoM*_g1[ix]-1.01*_f1[ix];
_g2[ix] = (4.05*_rhoE-0.09)*_g1[ix];
}
else if(id0==3212&&id1==2212) {
_f1[ix] = -_etaV/root2;
_g1[ix] = -_gA/root2*_etaA*(1.-2.*_alphaD);
_f2[ix] = 4.2*_rhoM*_g1[ix]-1.03*_f1[ix];
_g2[ix] = (4.2*_rhoE-0.12)*_g1[ix];
}
else if(id0==3112&&id1==2112) {
_f1[ix] = -_etaV;
_g1[ix] = -_gA*_etaA*(1.-2.*_alphaD);
_f2[ix] = 4.2*_rhoM*_g1[ix]-1.03*_f1[ix];
_g2[ix] = (4.2*_rhoE-0.12)*_g1[ix];
}
else if(id0==3312&&id1==3122) {
_f1[ix] = root32*_etaV;
_g1[ix] = _gA*root32*_etaA*(1.-4./3.*_alphaD);
_f2[ix] = 4.8*_rhoM*_g1[ix]-1.01*_f1[ix];
_g2[ix] = (4.8*_rhoE-0.08)*_g1[ix];
}
else if(id0==3312&&id1==3212) {
_f1[ix] = _etaV/root2;
_g1[ix] = _gA*_etaA/root2;
_f2[ix] = 4.95*_rhoM*_g1[ix]-1.*_f1[ix];
_g2[ix] = (4.95*_rhoE-0.05)*_g1[ix];
}
else if(id0==3322&&id1==3222) {
_f1[ix] = _etaV;
_g1[ix] = _gA*_etaA;
_f2[ix] = 4.95*_rhoM*_g1[ix]-1.*_f1[ix];
_g2[ix] = (4.95*_rhoE-0.05)*_g1[ix];
}
else {
throw InitException() << "Mode not recognised in BaryonSimpleFormFactor "
<< id0 << " " << id1
<< Exception::abortnow;
}
}
}
void BaryonSimpleFormFactor::persistentOutput(PersistentOStream & os) const {
os << _gA << _alphaD << _etaV << _etaA << _rhoE << _rhoM
<< _f1 << _f2 << _g1 << _g2;
}
void BaryonSimpleFormFactor::persistentInput(PersistentIStream & is, int) {
is >> _gA >> _alphaD >> _etaV >> _etaA >> _rhoE >> _rhoM
>> _f1 >> _f2 >> _g1 >> _g2;
}
// The following static variable is needed for the type
// description system in ThePEG.
DescribeClass<BaryonSimpleFormFactor,BaryonFormFactor>
describeHerwigBaryonSimpleFormFactor("Herwig::BaryonSimpleFormFactor",
"HwFormFactors.so");
void BaryonSimpleFormFactor::Init() {
static ClassDocumentation<BaryonSimpleFormFactor> documentation
("The BaryonSimpleFormFactor class implements the"
" quark model calculation of the form-factors from PRD25, 206",
"The BaryonSimpleFormFactor class which implements the results"
" of \\cite{Donoghue:1981uk}was used for the weak decays of the light baryons.",
"\\bibitem{Donoghue:1981uk}\n"
"J.~F.~Donoghue and B.~R.~Holstein,\n"
"Phys.\\ Rev.\\ D {\\bf 25} (1982) 206.\n"
"%%CITATION = PHRVA,D25,206;%%\n");
static Parameter<BaryonSimpleFormFactor,double> interfaceg_A
("g_A",
"The axial-vector coupling in neutron beta decay.",
&BaryonSimpleFormFactor::_gA, 1.25, 0.0, 10.0,
false, false, true);
static Parameter<BaryonSimpleFormFactor,double> interfacealpha_D
("alpha_D",
"SU(3) breaking parameter which is the ratio D/(D+F). ",
&BaryonSimpleFormFactor::_alphaD, 0.6, 0.0, 1.0,
false, false, true);
static Parameter<BaryonSimpleFormFactor,double> interfaceeta_V
("eta_V",
"The eta_V SU(3) breaking parameter",
&BaryonSimpleFormFactor::_etaV, .97, 0.0, 10.0,
false, false, true);
static Parameter<BaryonSimpleFormFactor,double> interfaceeta_A
("eta_A",
"The eta_A SU(3) breaking parameter",
&BaryonSimpleFormFactor::_etaA, 1.08, 0.0, 10.0,
false, false, true);
static Parameter<BaryonSimpleFormFactor,double> interfacerho_E
("rho_E",
"The SU(3) breaking parameter for the electric dipole moment.",
&BaryonSimpleFormFactor::_rhoE, 0.094, 0.0, 10.0,
false, false, true);
static Parameter<BaryonSimpleFormFactor,double> interfacerho_M
("rho_M",
"The SU(3) breaking parameter for the magentic dipole moment.",
&BaryonSimpleFormFactor::_rhoM, 0.860, 0.0, 10.0,
false, false, true);
}
void BaryonSimpleFormFactor::
SpinHalfSpinHalfFormFactor(Energy2,int iloc, int,int,Energy,Energy,
Complex & f1v,Complex & f2v,Complex & f3v,
Complex & f1a,Complex & f2a,Complex & f3a,
FlavourInfo,
Virtuality virt) {
assert(virt==SpaceLike);
useMe();
f1v = _f1[iloc];
f1a = -_g1[iloc];
f2v = -_f2[iloc];
f2a = _g2[iloc];
f3v = 0.;
f3a = 0.;
}
void BaryonSimpleFormFactor::dataBaseOutput(ofstream& output,bool header,
bool create) const {
if(header) output << "update decayers set parameters=\"";
if(create) output << "create Herwig::BaryonSimpleFormFactor "
<< name() << " \n";
output << "newdef " << name() << ":g_A " << _gA << " \n";
output << "newdef " << name() << ":alpha_D " << _alphaD << " \n";
output << "newdef " << name() << ":eta_V " << _etaV << " \n";
output << "newdef " << name() << ":eta_A " << _etaA << " \n";
output << "newdef " << name() << ":rho_E " << _rhoE << " \n";
output << "newdef " << name() << ":rho_M " << _rhoM << " \n";
BaryonFormFactor::dataBaseOutput(output,false,false);
if(header) output << "\n\" where BINARY ThePEGName=\""
<< fullName() << "\";" << endl;
}

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