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CzyzNucleonFormFactor.cc
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CzyzNucleonFormFactor.cc
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// -*- C++ -*-
//
// This is the implementation of the non-inlined, non-templated member
// functions of the CzyzNucleonFormFactor class.
//
#include "CzyzNucleonFormFactor.h"
#include "ThePEG/Interface/ClassDocumentation.h"
#include "ThePEG/EventRecord/Particle.h"
#include "ThePEG/Repository/UseRandom.h"
#include "ThePEG/Repository/EventGenerator.h"
#include "ThePEG/Utilities/DescribeClass.h"
#include "ThePEG/Persistency/PersistentOStream.h"
#include "ThePEG/Persistency/PersistentIStream.h"
#include "Herwig/Decay/ResonanceHelpers.h"
using namespace Herwig;
CzyzNucleonFormFactor::CzyzNucleonFormFactor() {
// masses and widths of rho resonances
rhoMasses_ = {775.49*MeV, 1465*MeV, 1720*MeV, 2.12*GeV,2.32647*GeV};
rhoWidths_ = {149.10*MeV, 400*MeV, 250*MeV, 0.3 *GeV,0.4473 *GeV};
// masses and width of omega resonances
omegaMasses_ = {782.65*MeV, 1425*MeV, 1670*MeV, 2.0707 *GeV, 2.34795 *GeV};
omegaWidths_ = {8.49 *MeV, 215*MeV, 315*MeV, 1.03535*GeV, 1.173975*GeV};
// c_1 couplings
c1Re_ = {1.,-0.467,-0.177, 0.301};
c1Im_ = {0.,-0.385, 0.149, 0.264};
// c_2 couplings
c2Re_ = {1., 0.0521, -0.00308,-0.348};
c2Im_ = {0.,-3.04, 2.38,-0.104};
// c_3 couplings
c3Re_ = {1.,-7.88,10.2};
c3Im_ = {0., 5.67, -1.94};
// c_4 couplings
c4Re_ = {1.,-0.832, 0.405};
c4Im_ = {0., 0.308,-0.25};
// Magnetic moments
mup_ = 2.792847356;
mun_ = -1.9130427;
// set up the form factors
addFormFactor(2212,2212,2,2,2,1,1,1);
addFormFactor(2112,2112,2,2,2,1,1,1);
initialModes(numberOfFactors());
}
IBPtr CzyzNucleonFormFactor::clone() const {
return new_ptr(*this);
}
IBPtr CzyzNucleonFormFactor::fullclone() const {
return new_ptr(*this);
}
void CzyzNucleonFormFactor::doinit() {
BaryonFormFactor::doinit();
static const Complex ii(0.,1.);
// calculate c_1
c1_.clear();
assert(c1Re_.size()==4 && c1Im_.size()==4);
// c_1 1 -> 4
complex<Energy2> fact(ZERO);
for(unsigned int ix=0;ix<4;++ix) {
c1_.push_back(c1Re_[ix]+ii*c1Im_[ix]);
fact += c1_[ix]*sqr(omegaMasses_[ix]);
}
c1_.push_back(-fact/sqr(omegaMasses_[4]));
// calculate c_2
c2_.clear();
assert(c2Re_.size()==4 && c2Im_.size()==4);
// c_2 1 -> 4
fact = ZERO;
for(unsigned int ix=0;ix<4;++ix) {
c2_.push_back(c2Re_[ix]+ii*c2Im_[ix]);
fact += c2_[ix]*sqr(rhoMasses_[ix]);
}
c2_.push_back(-fact/sqr(rhoMasses_[4]));
// calculate c_3
c3_.clear();
assert(c3Re_.size()==3 && c3Im_.size()==3);
// c_3 1 -> 4
fact = ZERO;
complex<Energy4> fact2(ZERO);
for(unsigned int ix=0;ix<3;++ix) {
c3_.push_back(c3Re_[ix]+ii*c3Im_[ix]);
fact += c3_[ix]*sqr(omegaMasses_[ix]);
fact2 += c3_[ix]*sqr(omegaMasses_[ix])*
(sqr(omegaMasses_[ix])-sqr(omegaMasses_[4])
+ii*(omegaMasses_[4]*omegaWidths_[4]-omegaMasses_[ix]*omegaWidths_[ix]));
}
c3_.push_back(fact2/sqr(omegaMasses_[3])/
(sqr(omegaMasses_[4])-sqr(omegaMasses_[3])
+ii*(omegaMasses_[3]*omegaWidths_[3]-omegaMasses_[4]*omegaWidths_[4])) );
fact += c3_[3]*sqr(omegaMasses_[3]);
c3_.push_back(-fact/sqr(omegaMasses_[4]));
// c_4 1 -> 4
fact = ZERO;
fact2 = ZERO;
for(unsigned int ix=0;ix<3;++ix) {
c4_.push_back(c4Re_[ix]+ii*c4Im_[ix]);
fact += c4_[ix]*sqr(rhoMasses_[ix]);
fact2 += c4_[ix]*sqr(rhoMasses_[ix])*
(sqr(rhoMasses_[ix])-sqr(rhoMasses_[4])
+ii*(rhoMasses_[4]*rhoWidths_[4]-rhoMasses_[ix]*rhoWidths_[ix]));
}
c4_.push_back(fact2/sqr(rhoMasses_[3])/
(sqr(rhoMasses_[4])-sqr(rhoMasses_[3])
+ii*(rhoMasses_[3]*rhoWidths_[3]-rhoMasses_[4]*rhoWidths_[4])) );
fact += c4_[3]*sqr(rhoMasses_[3]);
c4_.push_back(-fact/sqr(rhoMasses_[4]));
// a and b parameters
a_ = mup_-mun_-1;
b_ = -mup_-mun_+1.;
}
void CzyzNucleonFormFactor::persistentOutput(PersistentOStream & os) const {
os << ounit(rhoMasses_,GeV) << ounit(rhoWidths_,GeV)
<< ounit(omegaMasses_,GeV) << ounit(omegaWidths_,GeV)
<< c1Re_ << c1Im_ << c2Re_ << c2Im_
<< c3Re_ << c3Im_ << c4Re_ << c4Im_
<< c1_ << c2_ << c3_ << c4_
<< mup_ << mun_ << a_ << b_;
}
void CzyzNucleonFormFactor::persistentInput(PersistentIStream & is, int) {
is >> iunit(rhoMasses_,GeV) >> iunit(rhoWidths_,GeV)
>> iunit(omegaMasses_,GeV) >> iunit(omegaWidths_,GeV)
>> c1Re_ >> c1Im_ >> c2Re_ >> c2Im_
>> c3Re_ >> c3Im_ >> c4Re_ >> c4Im_
>> c1_ >> c2_ >> c3_ >> c4_
>> mup_ >> mun_ >> a_ >> b_;
}
// The following static variable is needed for the type
// description system in ThePEG.
DescribeClass<CzyzNucleonFormFactor,BaryonFormFactor>
describeHerwigCzyzNucleonFormFactor("Herwig::CzyzNucleonFormFactor",
"HwFormFactors.so");
void CzyzNucleonFormFactor::Init() {
static ClassDocumentation<CzyzNucleonFormFactor> documentation
("The CzyzNucleonFormFactor class implements the model of "
"Phys.Rev. D90 (2014) no.11, 114021 for the nucleon form factor",
"The nucleon form factor model of \\cite{Czyz:2014sha} was used",
"\\bibitem{Czyz:2014sha}\n"
"H.~Czyż, J.~H.~Kühn and S.~Tracz,\n"
"%``Nucleon form factors and final state radiative corrections to $e^+e^- \\to p\\bar{p}γ$,''\n"
"Phys.\\ Rev.\\ D {\\bf 90} (2014) no.11, 114021\n"
"doi:10.1103/PhysRevD.90.114021\n"
"[arXiv:1407.7995 [hep-ph]].\n"
"%%CITATION = doi:10.1103/PhysRevD.90.114021;%%\n"
"%5 citations counted in INSPIRE as of 25 Aug 2018\n");
static ParVector<CzyzNucleonFormFactor,Energy> interfaceRhoMasses
("RhoMasses",
"The masses of the rho mesons for the form factor",
&CzyzNucleonFormFactor::rhoMasses_, GeV, 5, 1.0*GeV, 0.0*GeV, 10.0*GeV,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,Energy> interfaceRhoWidths
("RhoWidths",
"The widths of the rho mesons for the form factor",
&CzyzNucleonFormFactor::rhoWidths_, GeV, 5, 1.0*GeV, 0.0*GeV, 10.0*GeV,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,Energy> interfaceOmegaMasses
("OmegaMasses",
"The masses of the omega mesons for the form factor",
&CzyzNucleonFormFactor::omegaMasses_, GeV, 5, 1.0*GeV, 0.0*GeV, 10.0*GeV,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,Energy> interfaceOmegaWidths
("OmegaWidths",
"The widths of the omega mesons for the form factor",
&CzyzNucleonFormFactor::omegaWidths_, GeV, 5, 1.0*GeV, 0.0*GeV, 10.0*GeV,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,double> interfacec1Real
("c1Real",
"The real part of the c_1 coupling",
&CzyzNucleonFormFactor::c1Re_, 4, 1., -100., 100.0,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,double> interfacec1Imag
("c1Imag",
"The imaginary part of the c_1 coupling",
&CzyzNucleonFormFactor::c1Im_, 4, 1., -100., 100.0,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,double> interfacec2Real
("c2Real",
"The real part of the c_2 coupling",
&CzyzNucleonFormFactor::c2Re_, 4, 1., -100., 100.0,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,double> interfacec2Imag
("c2Imag",
"The imaginary part of the c_2 coupling",
&CzyzNucleonFormFactor::c2Im_, 4, 1., -100., 100.0,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,double> interfacec3Real
("c3Real",
"The real part of the c_3 coupling",
&CzyzNucleonFormFactor::c3Re_, 3, 1., -100., 100.0,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,double> interfacec3Imag
("c3Imag",
"The imaginary part of the c_3 coupling",
&CzyzNucleonFormFactor::c3Im_, 3, 1., -100., 100.0,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,double> interfacec4Real
("c4Real",
"The real part of the c_4 coupling",
&CzyzNucleonFormFactor::c4Re_, 3, 1., -100., 100.0,
false, false, Interface::limited);
static ParVector<CzyzNucleonFormFactor,double> interfacec4Imag
("c4Imag",
"The imaginary part of the c_4 coupling",
&CzyzNucleonFormFactor::c4Im_, 3, 1., -100., 100.0,
false, false, Interface::limited);
static Parameter<CzyzNucleonFormFactor,double> interfaceMuProton
("MuProton",
"The proton magnetic moment",
&CzyzNucleonFormFactor::mup_, 2.792, 0.0, 10.0,
false, false, Interface::limited);
static Parameter<CzyzNucleonFormFactor,double> interfaceMuNeutron
("MuNeutron",
"The proton magnetic moment",
&CzyzNucleonFormFactor::mun_, -1.913, 0.0, 10.0,
false, false, Interface::limited);
}
void CzyzNucleonFormFactor::
SpinHalfSpinHalfFormFactor(Energy2 q2,int iloc, int id0,int id1,Energy,Energy,
Complex & f1v,Complex & f2v,Complex & f3v,
Complex & f1a,Complex & f2a,Complex & f3a,
Virtuality virt) {
assert(abs(id0)==abs(id1));
if(iloc==0) assert(abs(id0)==2212);
else assert(abs(id0)==2112);
assert(virt==TimeLike);
// calculate the form factors
Complex F1S(0.),F1V(0.),F2S(0.),F2V(0.);
Complex n1(0.),n2(0.),n3(0.),n4(0.);
for(unsigned int ix=0;ix<5;++ix) {
F1S += c1_[ix]*Resonance::BreitWignerFW(q2,omegaMasses_[ix],omegaWidths_[ix]);
F1V += c2_[ix]*Resonance::BreitWignerFW(q2, rhoMasses_[ix], rhoWidths_[ix]);
F2S += c3_[ix]*Resonance::BreitWignerFW(q2,omegaMasses_[ix],omegaWidths_[ix]);
F2V += c4_[ix]*Resonance::BreitWignerFW(q2, rhoMasses_[ix], rhoWidths_[ix]);
n1 += c1_[ix];
n2 += c2_[ix];
n3 += c3_[ix];
n4 += c4_[ix];
}
F1S *= 0.5 /n1;
F1V *= 0.5 /n2;
F2S *= -0.5*b_/n3;
F2V *= 0.5*a_/n4;
f1a = f2a = f3v = f3a = 0.;
if(iloc==0) {
f1v = F1S + F1V;
f2v = F2S + F2V;
}
else {
f1v = F1S - F1V;
f2v = F2S - F2V;
}
}
void CzyzNucleonFormFactor::
dataBaseOutput(ofstream& output,bool header,
bool create) const {
if(header) output << "update decayers set parameters=\"";
if(create) output << "create Herwig::CzyzNucleonFormFactor "
<< name() << " \n";
for(unsigned int ix=0;ix<5;++ix) {
output << "newdef " << name() << ":RhoMasses " << ix << " "
<< rhoMasses_[ix]/GeV << "\n";
output << "newdef " << name() << ":RhoWidths " << ix << " "
<< rhoWidths_[ix]/GeV << "\n";
output << "newdef " << name() << ":OmegaMasses " << ix << " "
<< omegaMasses_[ix]/GeV << "\n";
output << "newdef " << name() << ":OmegaWidths " << ix << " "
<< omegaWidths_[ix]/GeV << "\n";
}
for(unsigned int ix=0;ix<4;++ix) {
output << "newdef " << name() << ":c1Real " << ix << " "
<< c1Re_[ix] << "\n";
output << "newdef " << name() << ":c1Imag " << ix << " "
<< c1Im_[ix] << "\n";
output << "newdef " << name() << ":c2Real " << ix << " "
<< c2Re_[ix] << "\n";
output << "newdef " << name() << ":c2Imag " << ix << " "
<< c2Im_[ix] << "\n";
}
for(unsigned int ix=0;ix<3;++ix) {
output << "newdef " << name() << ":c3Real " << ix << " "
<< c3Re_[ix] << "\n";
output << "newdef " << name() << ":c3Imag " << ix << " "
<< c3Im_[ix] << "\n";
output << "newdef " << name() << ":c4Real " << ix << " "
<< c4Re_[ix] << "\n";
output << "newdef " << name() << ":c4Imag " << ix << " "
<< c4Im_[ix] << "\n";
}
output << "newdef " << name() << ":MuProton " << mup_ << "\n";
output << "newdef " << name() << ":MuNeutron " << mun_ << "\n";
BaryonFormFactor::dataBaseOutput(output,false,false);
if(header) output << "\n\" where BINARY ThePEGName=\""
<< fullName() << "\";" << endl;
}

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