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geant4/source/processes/hadronic/models/parton_string/qgsm/src/G4QGSMSplitableHadron.cc
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//
// ********************************************************************
// * DISCLAIMER *
// * *
// * The following disclaimer summarizes all the specific disclaimers *
// * of contributors to this software. The specific disclaimers,which *
// * govern, are listed with their locations in: *
// * http://cern.ch/geant4/license *
// * *
// * Neither the authors of this software system, nor their employing *
// * institutes,nor the agencies providing financial support for this *
// * work make any representation or warranty, express or implied, *
// * regarding this software system or assume any liability for its *
// * use. *
// * *
// * This code implementation is the intellectual property of the *
// * GEANT4 collaboration. *
// * By copying, distributing or modifying the Program (or any work *
// * based on the Program) you indicate your acceptance of this *
// * statement, and all its terms. *
// ********************************************************************
//
#include "G4QGSMSplitableHadron.hh"
#include "G4ParticleTable.hh"
#include "G4PionPlus.hh"
#include "G4PionMinus.hh"
#include "G4Gamma.hh"
#include "G4PionZero.hh"
#include "G4KaonPlus.hh"
#include "G4KaonMinus.hh"
// based on prototype by Maxim Komogorov
// Splitting into methods, and centralizing of model parameters HPW Feb 1999
// restructuring HPW Feb 1999
// fixing bug in the sampling of 'x', HPW Feb 1999
// fixing bug in sampling pz, HPW Feb 1999.
// Code now also good for p-nucleus scattering (before only p-p), HPW Feb 1999.
// Using Parton more directly, HPW Feb 1999.
// Shortening the algorithm for sampling x, HPW Feb 1999.
// sampling of x replaced by formula, taking X_min into account in the correlated sampling. HPW, Feb 1999.
// logic much clearer now. HPW Feb 1999
// Removed the ordering problem. No Direction needed in selection of valence quark types. HPW Mar'99.
// Fixing p-t distributions for scattering of nuclei.
// Separating out parameters.
void G4QGSMSplitableHadron::InitParameters()
{
// changing rapidity distribution for all
alpha = -0.5; // Note that this number is still assumed in the algorithm
// needs to be generalized.
// changing rapidity distribution for projectile like
beta = 2.5;// Note that this number is still assumed in the algorithm
// needs to be generalized.
theMinPz = 0.5*G4PionMinus::PionMinus()->GetPDGMass();
// theMinPz = 0.1*G4PionMinus::PionMinus()->GetPDGMass();
// theMinPz = G4PionMinus::PionMinus()->GetPDGMass();
// as low as possible, otherwise, we have unphysical boundary conditions in the sampling.
StrangeSuppress = 0.48;
sigmaPt = 0.*GeV; // widens eta slightly, if increased to 1.7,
// but Maxim's algorithm breaks energy conservation
// to be revised.
widthOfPtSquare = 0.01*GeV*GeV;
Direction = FALSE;
minTransverseMass = 1*keV;
}
G4QGSMSplitableHadron::G4QGSMSplitableHadron()
{
InitParameters();
}
G4QGSMSplitableHadron::G4QGSMSplitableHadron(const G4ReactionProduct & aPrimary, G4bool aDirection)
:G4VSplitableHadron(aPrimary)
{
InitParameters();
Direction = aDirection;
}
G4QGSMSplitableHadron::G4QGSMSplitableHadron(const G4ReactionProduct & aPrimary)
: G4VSplitableHadron(aPrimary)
{
InitParameters();
}
G4QGSMSplitableHadron::G4QGSMSplitableHadron(const G4Nucleon & aNucleon)
: G4VSplitableHadron(aNucleon)
{
InitParameters();
}
G4QGSMSplitableHadron::G4QGSMSplitableHadron(const G4Nucleon & aNucleon, G4bool aDirection)
: G4VSplitableHadron(aNucleon)
{
InitParameters();
Direction = aDirection;
}
G4QGSMSplitableHadron::~G4QGSMSplitableHadron(){}
const G4QGSMSplitableHadron & G4QGSMSplitableHadron::operator=(const G4QGSMSplitableHadron &)
{
throw G4HadronicException(__FILE__, __LINE__, "G4QGSMSplitableHadron::operator= meant to not be accessable");
return *this;
}
//**************************************************************************************************************************
void G4QGSMSplitableHadron::SplitUp()
{
if (IsSplit()) return;
Splitting();
if (Color.size()!=0) return;
if (GetSoftCollisionCount() == 0)
{
DiffractiveSplitUp();
}
else
{
SoftSplitUp();
}
}
void G4QGSMSplitableHadron::DiffractiveSplitUp()
{
// take the particle definitions and get the partons HPW
G4Parton * Left = NULL;
G4Parton * Right = NULL;
GetValenceQuarkFlavors(GetDefinition(), Left, Right);
Left->SetPosition(GetPosition());
Right->SetPosition(GetPosition());
G4LorentzVector HadronMom = Get4Momentum();
//std::cout << "DSU 1 - "<<HadronMom<<std::endl;
// momenta of string ends
G4double pt2 = HadronMom.perp2();
G4double transverseMass2 = HadronMom.plus()*HadronMom.minus();
G4double maxAvailMomentum2 = sqr(std::sqrt(transverseMass2) - std::sqrt(pt2));
G4ThreeVector pt(minTransverseMass, minTransverseMass, 0);
if(maxAvailMomentum2/widthOfPtSquare>0.01) pt = GaussianPt(widthOfPtSquare, maxAvailMomentum2);
//std::cout << "DSU 1.1 - "<< maxAvailMomentum2<< pt <<std::endl;
G4LorentzVector LeftMom(pt, 0.);
G4LorentzVector RightMom;
RightMom.setPx(HadronMom.px() - pt.x());
RightMom.setPy(HadronMom.py() - pt.y());
//std::cout << "DSU 2 - "<<RightMom<<" "<< LeftMom <<std::endl;
G4double Local1 = HadronMom.minus() + (RightMom.perp2() - LeftMom.perp2())/HadronMom.plus();
G4double Local2 = std::sqrt(std::max(0., sqr(Local1) - 4.*RightMom.perp2()*HadronMom.minus()/HadronMom.plus()));
//std::cout << "DSU 3 - "<< Local1 <<" "<< Local2 <<std::endl;
if (Direction) Local2 = -Local2;
G4double RightMinus = 0.5*(Local1 + Local2);
G4double LeftMinus = HadronMom.minus() - RightMinus;
//std::cout << "DSU 4 - "<< RightMinus <<" "<< LeftMinus << " "<<HadronMom.minus() <<std::endl;
G4double LeftPlus = LeftMom.perp2()/LeftMinus;
G4double RightPlus = HadronMom.plus() - LeftPlus;
//std::cout << "DSU 5 - "<< RightPlus <<" "<< LeftPlus <<std::endl;
LeftMom.setPz(0.5*(LeftPlus - LeftMinus));
LeftMom.setE (0.5*(LeftPlus + LeftMinus));
RightMom.setPz(0.5*(RightPlus - RightMinus));
RightMom.setE (0.5*(RightPlus + RightMinus));
//std::cout << "DSU 6 - "<< LeftMom <<" "<< RightMom <<std::endl;
Left->Set4Momentum(LeftMom);
Right->Set4Momentum(RightMom);
Color.push_back(Left);
AntiColor.push_back(Right);
}
void G4QGSMSplitableHadron::SoftSplitUp()
{
//... sample transversal momenta for sea and valence quarks
G4double phi, pts;
G4double SumPy = 0.;
G4double SumPx = 0.;
G4ThreeVector Pos = GetPosition();
G4int nSeaPair = GetSoftCollisionCount()-1;
// here the condition,to ensure viability of splitting, also in cases
// where difractive excitation occured together with soft scattering.
// G4double LightConeMomentum = (Direction)? Get4Momentum().plus() : Get4Momentum().minus();
// G4double Xmin = theMinPz/LightConeMomentum;
G4double Xmin = theMinPz/( Get4Momentum().e() - GetDefinition()->GetPDGMass() );
while(Xmin>=1-(2*nSeaPair+1)*Xmin) Xmin*=0.95;
G4int aSeaPair;
for (aSeaPair = 0; aSeaPair < nSeaPair; aSeaPair++)
{
// choose quark flavour, d:u:s = 1:1:(1/StrangeSuppress-2)
G4int aPDGCode = 1 + (G4int)(G4UniformRand()/StrangeSuppress);
// BuildSeaQuark() determines quark spin, isospin and colour
// via parton-constructor G4Parton(aPDGCode)
G4Parton * aParton = BuildSeaQuark(false, aPDGCode, nSeaPair);
// G4cerr << "G4QGSMSplitableHadron::SoftSplitUp()" << G4endl;
// G4cerr << "Parton 1: "
// << " PDGcode: " << aPDGCode
// << " - Name: " << aParton->GetDefinition()->GetParticleName()
// << " - Type: " << aParton->GetDefinition()->GetParticleType()
// << " - Spin-3: " << aParton->GetSpinZ()
// << " - Colour: " << aParton->GetColour() << G4endl;
// save colour a spin-3 for anti-quark
G4int firstPartonColour = aParton->GetColour();
G4double firstPartonSpinZ = aParton->GetSpinZ();
SumPx += aParton->Get4Momentum().px();
SumPy += aParton->Get4Momentum().py();
Color.push_back(aParton);
// create anti-quark
aParton = BuildSeaQuark(true, aPDGCode, nSeaPair);
aParton->SetSpinZ(-firstPartonSpinZ);
aParton->SetColour(-firstPartonColour);
// G4cerr << "Parton 2: "
// << " PDGcode: " << -aPDGCode
// << " - Name: " << aParton->GetDefinition()->GetParticleName()
// << " - Type: " << aParton->GetDefinition()->GetParticleType()
// << " - Spin-3: " << aParton->GetSpinZ()
// << " - Colour: " << aParton->GetColour() << G4endl;
// G4cerr << "------------" << G4endl;
SumPx += aParton->Get4Momentum().px();
SumPy += aParton->Get4Momentum().py();
AntiColor.push_back(aParton);
}
// Valence quark
G4Parton* pColorParton = NULL;
G4Parton* pAntiColorParton = NULL;
GetValenceQuarkFlavors(GetDefinition(), pColorParton, pAntiColorParton);
G4int ColorEncoding = pColorParton->GetPDGcode();
G4int AntiColorEncoding = pAntiColorParton->GetPDGcode();
pts = sigmaPt*std::sqrt(-std::log(G4UniformRand()));
phi = 2.*pi*G4UniformRand();
G4double Px = pts*std::cos(phi);
G4double Py = pts*std::sin(phi);
SumPx += Px;
SumPy += Py;
if (ColorEncoding < 0) // use particle definition
{
G4LorentzVector ColorMom(-SumPx, -SumPy, 0, 0);
pColorParton->Set4Momentum(ColorMom);
G4LorentzVector AntiColorMom(Px, Py, 0, 0);
pAntiColorParton->Set4Momentum(AntiColorMom);
}
else
{
G4LorentzVector ColorMom(Px, Py, 0, 0);
pColorParton->Set4Momentum(ColorMom);
G4LorentzVector AntiColorMom(-SumPx, -SumPy, 0, 0);
pAntiColorParton->Set4Momentum(AntiColorMom);
}
Color.push_back(pColorParton);
AntiColor.push_back(pAntiColorParton);
// Sample X
G4int nAttempt = 0;
G4double SumX = 0;
G4double aBeta = beta;
G4double ColorX, AntiColorX;
G4double HPWtest = 0;
if (GetDefinition() == G4PionMinus::PionMinusDefinition()) aBeta = 1.;
if (GetDefinition() == G4Gamma::GammaDefinition()) aBeta = 1.;
if (GetDefinition() == G4PionPlus::PionPlusDefinition()) aBeta = 1.;
if (GetDefinition() == G4PionZero::PionZeroDefinition()) aBeta = 1.;
if (GetDefinition() == G4KaonPlus::KaonPlusDefinition()) aBeta = 0.;
if (GetDefinition() == G4KaonMinus::KaonMinusDefinition()) aBeta = 0.;
do
{
SumX = 0;
nAttempt++;
G4int NumberOfUnsampledSeaQuarks = 2*nSeaPair;
G4double beta1 = beta;
if (std::abs(ColorEncoding) <= 1000 && std::abs(AntiColorEncoding) <= 1000) beta1 = 1.; //... in a meson
ColorX = SampleX(Xmin, NumberOfUnsampledSeaQuarks, 2*nSeaPair, aBeta);
HPWtest = ColorX;
while (ColorX < Xmin || ColorX > 1.|| 1. - ColorX <= Xmin);
Color.back()->SetX(SumX = ColorX);// this is the valenz quark.
for(G4int aPair = 0; aPair < nSeaPair; aPair++)
{
NumberOfUnsampledSeaQuarks--;
ColorX = SampleX(Xmin, NumberOfUnsampledSeaQuarks, 2*nSeaPair, aBeta);
Color[aPair]->SetX(ColorX);
SumX += ColorX;
NumberOfUnsampledSeaQuarks--;
AntiColorX = SampleX(Xmin, NumberOfUnsampledSeaQuarks, 2*nSeaPair, aBeta);
AntiColor[aPair]->SetX(AntiColorX); // the 'sea' partons
SumX += AntiColorX;
if (1. - SumX <= Xmin) break;
}
}
while (1. - SumX <= Xmin);
(*(AntiColor.end()-1))->SetX(1. - SumX); // the di-quark takes the rest, then go to momentum
/// and here is the bug ;-) @@@@@@@@@@@@@
if(getenv("debug_QGSMSplitableHadron") )G4cout << "particle energy at split = "<<Get4Momentum().t()<<G4endl;
G4double lightCone = ((!Direction) ? Get4Momentum().minus() : Get4Momentum().plus());
// lightCone -= 0.5*Get4Momentum().m();
// hpw testing @@@@@ lightCone = 2.*Get4Momentum().t();
if(getenv("debug_QGSMSplitableHadron") )G4cout << "Light cone = "<<lightCone<<G4endl;
for(aSeaPair = 0; aSeaPair < nSeaPair+1; aSeaPair++)
{
G4Parton* aParton = Color[aSeaPair];
aParton->DefineMomentumInZ(lightCone, Direction);
aParton = AntiColor[aSeaPair];
aParton->DefineMomentumInZ(lightCone, Direction);
}
//--DEBUG-- cout <<G4endl<<"XSAMPLE "<<HPWtest<<G4endl;
return;
}
void G4QGSMSplitableHadron::GetValenceQuarkFlavors(const G4ParticleDefinition * aPart, G4Parton *& Parton1, G4Parton *& Parton2)
{
// Note! convention aEnd = q or (qq)bar and bEnd = qbar or qq.
G4int aEnd;
G4int bEnd;
G4int HadronEncoding = aPart->GetPDGEncoding();
if (aPart->GetBaryonNumber() == 0)
{
theMesonSplitter.SplitMeson(HadronEncoding, &aEnd, &bEnd);
}
else
{
theBaryonSplitter.SplitBarion(HadronEncoding, &aEnd, &bEnd);
}
Parton1 = new G4Parton(aEnd);
Parton1->SetPosition(GetPosition());
// G4cerr << "G4QGSMSplitableHadron::GetValenceQuarkFlavors()" << G4endl;
// G4cerr << "Parton 1: "
// << " PDGcode: " << aEnd
// << " - Name: " << Parton1->GetDefinition()->GetParticleName()
// << " - Type: " << Parton1->GetDefinition()->GetParticleType()
// << " - Spin-3: " << Parton1->GetSpinZ()
// << " - Colour: " << Parton1->GetColour() << G4endl;
Parton2 = new G4Parton(bEnd);
Parton2->SetPosition(GetPosition());
// G4cerr << "Parton 2: "
// << " PDGcode: " << bEnd
// << " - Name: " << Parton2->GetDefinition()->GetParticleName()
// << " - Type: " << Parton2->GetDefinition()->GetParticleType()
// << " - Spin-3: " << Parton2->GetSpinZ()
// << " - Colour: " << Parton2->GetColour() << G4endl;
// G4cerr << "... now checking for color and spin conservation - yielding: " << G4endl;
// colour of parton 1 choosen at random by G4Parton(aEnd)
// colour of parton 2 is the opposite:
Parton2->SetColour(-(Parton1->GetColour()));
// isospin-3 of both partons is handled by G4Parton(PDGCode)
// spin-3 of parton 1 and 2 choosen at random by G4Parton(aEnd)
// spin-3 of parton 2 may be constrained by spin of original particle:
if ( std::abs(Parton1->GetSpinZ() + Parton2->GetSpinZ()) > aPart->GetPDGSpin())
{
Parton2->SetSpinZ(-(Parton2->GetSpinZ()));
}
// G4cerr << "Parton 2: "
// << " PDGcode: " << bEnd
// << " - Name: " << Parton2->GetDefinition()->GetParticleName()
// << " - Type: " << Parton2->GetDefinition()->GetParticleType()
// << " - Spin-3: " << Parton2->GetSpinZ()
// << " - Colour: " << Parton2->GetColour() << G4endl;
// G4cerr << "------------" << G4endl;
}
G4ThreeVector G4QGSMSplitableHadron::GaussianPt(G4double widthSquare, G4double maxPtSquare)
{
G4double R;
while((R = -widthSquare*std::log(G4UniformRand())) > maxPtSquare);
R = std::sqrt(R);
G4double phi = twopi*G4UniformRand();
return G4ThreeVector (R*std::cos(phi), R*std::sin(phi), 0.);
}
G4Parton * G4QGSMSplitableHadron::
BuildSeaQuark(G4bool isAntiQuark, G4int aPDGCode, G4int /* nSeaPair*/)
{
if (isAntiQuark) aPDGCode*=-1;
G4Parton* result = new G4Parton(aPDGCode);
result->SetPosition(GetPosition());
G4ThreeVector aPtVector = GaussianPt(sigmaPt, DBL_MAX);
G4LorentzVector a4Momentum(aPtVector, 0);
result->Set4Momentum(a4Momentum);
return result;
}
G4double G4QGSMSplitableHadron::
SampleX(G4double anXmin, G4int nSea, G4int totalSea, G4double aBeta)
{
G4double result;
G4double x1, x2;
G4double ymax = 0;
for(G4int ii=0; ii<100; ii++)
{
G4double y = std::pow(1./G4double(ii), alpha);
y *= std::pow( std::pow(1-anXmin-totalSea*anXmin, alpha+1) - std::pow(anXmin, alpha+1), nSea);
y *= std::pow(1-anXmin-totalSea*anXmin, aBeta+1) - std::pow(anXmin, aBeta+1);
if(y>ymax) ymax = y;
}
G4double y;
do
{
x1 = -1.;
G4int debcount=0;
while(x1<anXmin||x1>=1-(totalSea+1)*anXmin)
{
debcount ++;
if(debcount>10000)
{
G4cout << "anXmin = "<<anXmin<<" nSea = "<<nSea<<" totalSea = "<< totalSea<<G4endl;
throw G4HadronicException(__FILE__, __LINE__, "G4QGSMSplitableHadron - Fatal: Cannot sample parton densities under these constraints.");
}
x1 = G4UniformRand();
}
y = std::pow(x1, alpha);
y *= std::pow( std::pow(1-x1-totalSea*anXmin, alpha+1) - std::pow(anXmin, alpha+1), nSea);
y *= std::pow(1-x1-totalSea*anXmin, aBeta+1) - std::pow(anXmin, aBeta+1);
x2 = ymax*G4UniformRand();
}
while(x2>y);
result = x1;
return result;
}
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