Gabriele Cosmo
439 lines
17 KiB
C++
439 lines
17 KiB
C++
//
|
|
// ********************************************************************
|
|
// * License and Disclaimer *
|
|
// * *
|
|
// * The Geant4 software is copyright of the Copyright Holders of *
|
|
// * the Geant4 Collaboration. It is provided under the terms and *
|
|
// * conditions of the Geant4 Software License, included in the file *
|
|
// * LICENSE and available at http://cern.ch/geant4/license . These *
|
|
// * include a list of copyright holders. *
|
|
// * *
|
|
// * 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. Please see the license in the file LICENSE and URL above *
|
|
// * for the full disclaimer and the limitation of liability. *
|
|
// * *
|
|
// * This code implementation is the result of the scientific and *
|
|
// * technical work of the GEANT4 collaboration. *
|
|
// * By using, copying, modifying or distributing the software (or *
|
|
// * any work based on the software) you agree to acknowledge its *
|
|
// * use in resulting scientific publications, and indicate your *
|
|
// * acceptance of all terms of the Geant4 Software license. *
|
|
// ********************************************************************
|
|
//
|
|
#include "G4QGSMSplitableHadron.hh"
|
|
#include "G4PhysicalConstants.hh"
|
|
#include "G4SystemOfUnits.hh"
|
|
#include "G4ParticleTable.hh"
|
|
#include "G4PionPlus.hh"
|
|
#include "G4PionMinus.hh"
|
|
#include "G4Gamma.hh"
|
|
#include "G4PionZero.hh"
|
|
#include "G4KaonPlus.hh"
|
|
#include "G4KaonMinus.hh"
|
|
|
|
#include "G4Log.hh"
|
|
#include "G4Pow.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(){}
|
|
|
|
//**************************************************************************************************************************
|
|
|
|
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; /* Loop checking, 26.10.2015, A.Ribon */
|
|
|
|
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();
|
|
|
|
pts = sigmaPt*std::sqrt(-G4Log(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;
|
|
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.;
|
|
const G4int maxNumberOfAttempts = 1000;
|
|
do
|
|
{
|
|
SumX = 0;
|
|
nAttempt++;
|
|
G4int NumberOfUnsampledSeaQuarks = 2*nSeaPair;
|
|
ColorX = SampleX(Xmin, NumberOfUnsampledSeaQuarks, 2*nSeaPair, aBeta);
|
|
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) && nAttempt < maxNumberOfAttempts ); /* Loop checking, 26.10.2015, A.Ribon */
|
|
if ( nAttempt >= maxNumberOfAttempts ) return;
|
|
|
|
(*(AntiColor.end()-1))->SetX(1. - SumX); // the di-quark takes the rest, then go to momentum
|
|
G4double lightCone = ((!Direction) ? Get4Momentum().minus() : Get4Momentum().plus());
|
|
G4double lightCone2 = ((!Direction) ? Get4Momentum().plus() : Get4Momentum().minus());
|
|
for(aSeaPair = 0; aSeaPair < nSeaPair+1; aSeaPair++)
|
|
{
|
|
G4Parton* aParton = Color[aSeaPair];
|
|
aParton->DefineMomentumInZ(lightCone, lightCone2, Direction);
|
|
|
|
aParton = AntiColor[aSeaPair];
|
|
aParton->DefineMomentumInZ(lightCone, lightCone2, Direction);
|
|
}
|
|
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;
|
|
const G4int maxNumberOfLoops = 1000;
|
|
G4int loopCounter = -1;
|
|
while ( ((R = -widthSquare*G4Log(G4UniformRand())) > maxPtSquare) && /* Loop checking, 26.10.2015, A.Ribon */
|
|
++loopCounter < maxNumberOfLoops ) {;}
|
|
if ( loopCounter >= maxNumberOfLoops ) R = 0.0;
|
|
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=1; ii<100; ii++)
|
|
{
|
|
G4double y = G4Pow::GetInstance()->powA(1./G4double(ii), alpha);
|
|
y *= G4Pow::GetInstance()->powN( G4Pow::GetInstance()->powA(1-anXmin-totalSea*anXmin, alpha+1) - G4Pow::GetInstance()->powA(anXmin, alpha+1), nSea);
|
|
y *= G4Pow::GetInstance()->powA(1-anXmin-totalSea*anXmin, aBeta+1) - G4Pow::GetInstance()->powA(anXmin, aBeta+1);
|
|
if(y>ymax) ymax = y;
|
|
}
|
|
G4double y;
|
|
G4double xMax=1-(totalSea+1)*anXmin;
|
|
if(anXmin > xMax)
|
|
{
|
|
G4cout << "anXmin = "<<anXmin<<" nSea = "<<nSea<<" totalSea = "<< totalSea<<G4endl;
|
|
throw G4HadronicException(__FILE__, __LINE__, "G4QGSMSplitableHadron - Fatal: Cannot sample parton densities under these constraints.");
|
|
}
|
|
const G4int maxNumberOfLoops = 10000;
|
|
G4int loopCounter = -1;
|
|
do
|
|
{
|
|
x1 = G4RandFlat::shoot(anXmin, xMax);
|
|
y = G4Pow::GetInstance()->powA(x1, alpha);
|
|
y *= G4Pow::GetInstance()->powN( G4Pow::GetInstance()->powA(1-x1-totalSea*anXmin, alpha+1) - G4Pow::GetInstance()->powA(anXmin, alpha+1), nSea);
|
|
y *= G4Pow::GetInstance()->powA(1-x1-totalSea*anXmin, aBeta+1) - G4Pow::GetInstance()->powA(anXmin, aBeta+1);
|
|
x2 = ymax*G4UniformRand();
|
|
} while ( (x2>y) && ++loopCounter < maxNumberOfLoops ); /* Loop checking, 26.10.2015, A.Ribon */
|
|
if ( loopCounter >= maxNumberOfLoops ) {
|
|
G4ExceptionDescription ed;
|
|
ed << " Failed sampling after maxNumberOfLoops attempts : forced exit! " << G4endl;
|
|
G4Exception( "G4QGSMSplitableHadron::SampleX ", "HAD_QGS_002", JustWarning, ed );
|
|
}
|
|
result = x1;
|
|
return result;
|
|
}
|
|
|