[u/mrichter/AliRoot.git] / EVGEN / AliGenDeuteron.cxx

/**************************************************************************
 * Copyright(c) 2009-2010, ALICE Experiment at CERN, All rights reserved. *
 *                                                                        *
 * Author: The ALICE Off-line Project.                                    *
 * Contributors are mentioned in the code where appropriate.              *
 *                                                                        *
 * Permission to use, copy, modify and distribute this software and its   *
 * documentation strictly for non-commercial purposes is hereby granted   *
 * without fee, provided that the above copyright notice appears in all   *
 * copies and that both the copyright notice and this permission notice   *
 * appear in the supporting documentation. The authors make no claims     *
 * about the suitability of this software for any purpose. It is          *
 * provided "as is" without express or implied warranty.                  *
 **************************************************************************/

//////////////////////////////////////////////////////////////////////////
// Afterburner to generate (anti)deuterons simulating coalescence of
// (anti)nucleons as in A. J. Baltz et al., Phys. lett B 325(1994)7.
// If the nucleon generator does not provide a spatial description of 
// the source the afterburner can provide one.
//
// There two options for the source: a thermal picture where all nucleons
// are placed randomly and homogeneously in an spherical volume, or
// an expansion one where they are projected onto its surface.
//
// An (anti)deuteron will form if there is a pair of (anti)proton-(anti)neutron
// with momentum difference less than ~ 300MeV and relative distance less than
// ~ 2.1fm. Only 3/4 of these clusters are accepted due to the deuteron spin.
//
// When there are more than one pair fulfilling the coalescence conditions,
// the selected pair can be the one with the first partner, with
// the lowest relative momentum, the lowest relative distance or both.
//////////////////////////////////////////////////////////////////////////

// Author: Eulogio Serradilla <eulogio.serradilla@ciemat.es>,
//         Arturo Menchaca <menchaca@fisica.unam.mx>
//

#include "Riostream.h"
#include "TParticle.h"
#include "AliStack.h"
#include "AliRun.h"
#include "TMath.h"
#include "TMCProcess.h"
#include "TList.h"
#include "TVector3.h"
#include "AliMC.h"
#include "TArrayF.h"
#include "AliCollisionGeometry.h"
#include "AliGenCocktailEventHeader.h"
#include "AliGenCocktailEntry.h"
#include "AliGenCocktailAfterBurner.h"
#include "AliGenDeuteron.h"
#include "AliLog.h"

ClassImp(AliGenDeuteron)

AliGenDeuteron::AliGenDeuteron(Int_t sign, Double_t pmax, Double_t rmax, Int_t cluster)
 :fSign(1)
 ,fPmax(pmax)
 ,fRmax(rmax)
 ,fSpinProb(1)
 ,fClusterType(cluster)
 ,fModel(0)
 ,fTimeLength(2.5)
 ,fB(0)
 ,fR(0)
 ,fPsiR(0)
 ,fCurStack(0)
 ,fNtrk(0)
{
//
// constructor
//
	fSign = sign > 0 ? 1:-1;
	
}

AliGenDeuteron::~AliGenDeuteron()
{
//
// Default destructor
//
}

void AliGenDeuteron::Init()
{
//
// Standard AliGenerator initializer
//
}

void AliGenDeuteron::Generate()
{
//
// Look for coalescence of (anti)nucleons in the nucleon source
// provided by the generator cocktail
//
	AliInfo(Form("sign: %d, Pmax: %g GeV/c, Rmax: %g fm, cluster: %d",fSign, fPmax, fRmax, fClusterType));
	if(fModel!=kNone) AliInfo(Form("model: %d, time: %g fm/c", fModel, fTimeLength));
	
	AliGenCocktailAfterBurner* gener = (AliGenCocktailAfterBurner*)gAlice->GetMCApp()->Generator();
	
	// find nuclear radius, only for first generator and projectile=target
	Bool_t collisionGeometry=0;
	if(fModel != kNone && gener->FirstGenerator()->Generator()->ProvidesCollisionGeometry())
	{
		TString name;
		Int_t ap, zp, at, zt;
		gener->FirstGenerator()->Generator()->GetProjectile(name,ap,zp);
		gener->FirstGenerator()->Generator()->GetTarget(name,at,zt);
		if(ap != at) AliWarning("projectile and target have different size");
		fR = 1.29*TMath::Power(at, 1./3.);
		collisionGeometry = 1;
	}
	
	for(Int_t ns = 0; ns < gener->GetNumberOfEvents(); ++ns)
	{
		gener->SetActiveEventNumber(ns);
		
		if(fModel != kNone && collisionGeometry)
		{
			fPsiR = (gener->GetCollisionGeometry(ns))->ReactionPlaneAngle();
			fB = (gener->GetCollisionGeometry(ns))->ImpactParameter();
			
			if(fB >= 2.*fR) continue; // no collision
		}
		
		fCurStack = gener->GetStack(ns);
		if(!fCurStack)
		{
			AliWarning("no event stack");
			return;
		}
		
		TList* protons = new TList();
		protons->SetOwner(kFALSE);
		TList* neutrons = new TList();
		neutrons->SetOwner(kFALSE);
		
		// particles produced by the generator
		for (Int_t i=0; i < fCurStack->GetNprimary(); ++i)
		{
			TParticle* iParticle = fCurStack->Particle(i);
			
			if(iParticle->GetStatusCode() != 1) continue;
			
			Int_t pdgCode = iParticle->GetPdgCode();
			if(pdgCode == fSign*2212)// (anti)proton
			{
				FixProductionVertex(iParticle);
				protons->Add(iParticle);
			}
			else if(pdgCode == fSign*2112) // (anti)neutron
			{
				FixProductionVertex(iParticle);
				neutrons->Add(iParticle);
			}
		}
		
		// look for clusters
		if(fClusterType==kFirstPartner)
		{
			FirstPartner(protons, neutrons);
		}
		else
		{
			WeightMatrix(protons, neutrons);
		}
		
		protons->Clear("nodelete");
		neutrons->Clear("nodelete");
		
		delete protons;
		delete neutrons;
	}
	
	AliInfo("DONE");
}

Double_t AliGenDeuteron::GetCoalescenceProbability(const TParticle* nucleon1, const TParticle* nucleon2) const
{
//
// Coalescence conditions as in
// A. J. Baltz et al., Phys. lett B 325(1994)7
//
// returns < 0 if coalescence is not possible
// otherwise returns a coalescence probability
//
	const Double_t kProtonMass  = 0.938272013;
	const Double_t kNeutronMass = 0.939565378;
	
	TVector3 v1(nucleon1->Vx(), nucleon1->Vy(), nucleon1->Vz());
	TVector3 p1(nucleon1->Px(), nucleon1->Py(), nucleon1->Pz());
	
	TVector3 v2(nucleon2->Vx(), nucleon2->Vy(), nucleon2->Vz());
	TVector3 p2(nucleon2->Px(), nucleon2->Py(), nucleon2->Pz());
	
	Double_t deltaP = 2.*this->GetPcm(p1, kProtonMass, p2, kNeutronMass); // relative momentum in CM frame
	if( deltaP >= fPmax) return -1.;
	
	Double_t deltaR = (v2-v1).Mag();       // relative distance (cm)
	if(deltaR >= fRmax*1.e-13) return -1.;
	
	if(Rndm() > fSpinProb)    return -1.;  // spin
	
	if(fClusterType == kLowestMomentum) return 1. - deltaP/fPmax;
	if(fClusterType == kLowestDistance) return 1. - 1.e+13*deltaR/fRmax;
	
	return 1. - 1.e+13*(deltaP*deltaR)/(fRmax*fPmax);
}

void AliGenDeuteron::FirstPartner(const TList* protons, TList* neutrons)
{
//
// Clusters are made with the first nucleon pair that fulfill
// the coalescence conditions, starting with the protons
//
	TIter p_next(protons);
	while(TParticle* n0 = (TParticle*) p_next())
	{
		TParticle* partner = 0;
		TIter n_next(neutrons);
		while(TParticle* n1 = (TParticle*) n_next() )
		{
			if(GetCoalescenceProbability(n0, n1) < 0 ) continue; // with next neutron
			partner = n1;
			break;
		}
		
		if(partner == 0) continue; // with next proton
		
		PushDeuteron(n0, partner);
		
		// Remove from the list for the next iteration
		neutrons->Remove(partner);
	}
}

void AliGenDeuteron::WeightMatrix(const TList* protons, const TList* neutrons)
{
//
// Build all possible nucleon pairs with their own probability
// and select only those with the highest coalescence probability
//
	Int_t nMaxPairs = protons->GetSize()*neutrons->GetSize();
	
	TParticle** cProton = new TParticle*[nMaxPairs];
	TParticle** cNeutron = new TParticle*[nMaxPairs];
	Double_t*  cWeight = new Double_t[nMaxPairs];
	
	// build all pairs with probability > 0
	Int_t cIdx = -1;
	TIter p_next(protons);
	while(TParticle* n1 = (TParticle*) p_next())
	{
		TIter n_next(neutrons);
		while(TParticle* n2 = (TParticle*) n_next() )
		{
			Double_t weight = this->GetCoalescenceProbability(n1,n2);
			if(weight < 0) continue;
			++cIdx;
			cProton[cIdx]  = n1;
			cNeutron[cIdx] = n2;
			cWeight[cIdx]  = weight;
		}
		n_next.Reset();
	}
	p_next.Reset();
	
	Int_t nPairs = cIdx + 1;
	
	// find the interacting pairs:
	// remove repeated pairs and select only
	// the pair with the highest coalescence probability
	
	Int_t nMaxIntPair = TMath::Min(protons->GetSize(), neutrons->GetSize());
	
	TParticle** iProton = new TParticle*[nMaxIntPair];
	TParticle** iNeutron = new TParticle*[nMaxIntPair];
	Double_t* iWeight = new Double_t[nMaxIntPair];
	
	Int_t iIdx = -1;
	while(kTRUE)
	{
		Int_t j = -1;
		Double_t wMax = 0;
		for(Int_t i=0; i < nPairs; ++i)
		{
			if(cWeight[i] > wMax)
			{
				wMax=cWeight[i];
				j = i;
			}
		}
		
		if(j == -1 ) break; // end
		
		// Save the interacting pair
		++iIdx;
		iProton[iIdx]  = cProton[j];
		iNeutron[iIdx] = cNeutron[j];
		iWeight[iIdx]  = cWeight[j];
		
		// invalidate all combinations with these pairs for the next iteration
		for(Int_t i=0; i < nPairs; ++i)
		{
			if(cProton[i] == iProton[iIdx]) cWeight[i] = -1.;
			if(cNeutron[i] == iNeutron[iIdx]) cWeight[i] = -1.;
		}
	}
	
	Int_t nIntPairs = iIdx + 1;
	
	delete[] cProton;
	delete[] cNeutron;
	delete[] cWeight;
	
	// Add the (anti)deuterons to the current event stack
	for(Int_t i=0; i<nIntPairs; ++i)
	{
		TParticle* n1 = iProton[i];
		TParticle* n2 = iNeutron[i];
		PushDeuteron(n1,n2);
	}
	
	delete[] iProton;
	delete[] iNeutron;
	delete[] iWeight;
}

void AliGenDeuteron::PushDeuteron(TParticle* parent1, TParticle* parent2)
{
//
// Create an (anti)deuteron from parent1 and parent2,
// add to the current stack and set kDoneBit for the parents
//
	const Double_t kDeuteronMass = 1.87561282;
	const Int_t kDeuteronPdg = 1000010020;
	
	// momentum
	TVector3 p1(parent1->Px(), parent1->Py(), parent1->Pz());
	TVector3 p2(parent2->Px(), parent2->Py(), parent2->Pz());
	TVector3 pN = p1+p2;
	
	// production vertex same as the parent1's
	TVector3 vN(parent1->Vx(), parent1->Vy(), parent1->Vz());
	
	// E^2 = p^2 + m^2
	Double_t energy = TMath::Sqrt(pN.Mag2() + kDeuteronMass*kDeuteronMass);
	
	// Add a new (anti)deuteron to current event stack
	fCurStack->PushTrack(1, -1, fSign*kDeuteronPdg,
	                 pN.X(), pN.Y(), pN.Z(), energy,
	                 vN.X(), vN.Y(), vN.Z(), parent1->T(),
	                 0., 0., 0., kPNCapture, fNtrk, 1., 0);
	
	// Set kDoneBit for the parents
	parent1->SetBit(kDoneBit);
	parent2->SetBit(kDoneBit);
}

void AliGenDeuteron::FixProductionVertex(TParticle* i)
{
//
// Replace current generator nucleon spatial distribution
// with a custom distribution according to the selected model
//
	if(fModel == kNone || fModel > kExpansion) return;
	
	// semi-axis from collision geometry (fm)
	Double_t a = fTimeLength + TMath::Sqrt(fR*fR - fB*fB/4.);
	Double_t b = fTimeLength + fR - fB/2.;
	Double_t c = fTimeLength;
	
	Double_t xx = 0;
	Double_t yy = 0;
	Double_t zz = 0;
	
	if(fModel == kThermal)
	{
		// uniformly ditributed in the volume on an ellipsoid
		// random (r,theta,phi) unit sphere
		Double_t r = TMath::Power(Rndm(),1./3.);
		Double_t theta = TMath::ACos(2.*Rndm()-1.);
		Double_t phi = 2.*TMath::Pi()*Rndm();
		
		// transform coordenates
		xx = a*r*TMath::Sin(theta)*TMath::Cos(phi);
		yy = b*r*TMath::Sin(theta)*TMath::Sin(phi);
		zz = c*r*TMath::Cos(theta);
	}
	else if(fModel == kExpansion)
	{
		// project into the surface of an ellipsoid
		xx = a*TMath::Sin(i->Theta())*TMath::Cos(i->Phi());
		yy = b*TMath::Sin(i->Theta())*TMath::Sin(i->Phi());
		zz = c*TMath::Cos(i->Theta());
	}
	
	// rotate by the reaction plane angle
	Double_t x = xx*TMath::Cos(fPsiR)+yy*TMath::Sin(fPsiR);
	Double_t y = -xx*TMath::Sin(fPsiR)+yy*TMath::Cos(fPsiR);
	Double_t z = zz;
	
	// translate by the production vertex (cm)
	i->SetProductionVertex(i->Vx() + 1.e-13*x, i->Vy() + 1.e-13*y, i->Vz() + 1.e-13*z, i->T());
}

Double_t AliGenDeuteron::GetS(Double_t p1x, Double_t p1y, Double_t p1z, Double_t m1, Double_t p2x, Double_t p2y, Double_t p2z, Double_t m2) const
{
//
// square of the center of mass energy
//
	Double_t E1 = TMath::Sqrt( p1x*p1x + p1y*p1y + p1z*p1z + m1*m1);
	Double_t E2 = TMath::Sqrt( p2x*p2x + p2y*p2y + p2z*p2z + m2*m2);
	
	return (E1+E2)*(E1+E2) - ((p1x+p2x)*(p1x+p2x) + (p1y+p2y)*(p1y+p2y) + (p1z+p2z)*(p1z+p2z));
}

Double_t AliGenDeuteron::GetPcm(Double_t p1x, Double_t p1y, Double_t p1z, Double_t m1, Double_t p2x, Double_t p2y, Double_t p2z, Double_t m2) const
{
//
// momentum in the CM frame
//
	Double_t s = this->GetS(p1x, p1y, p1z, m1, p2x, p2y, p2z, m2);
	
	return TMath::Sqrt( (s-(m1-m2)*(m1-m2))*(s-(m1+m2)*(m1+m2)) )/(2.*TMath::Sqrt(s));
}

Double_t AliGenDeuteron::GetPcm(const TVector3& p1, Double_t m1, const TVector3& p2, Double_t m2) const
{
//
// momentum in the CM frame
//
	return this->GetPcm(p1.Px(),p1.Py(),p1.Pz(),m1,p2.Px(),p2.Py(),p2.Pz(),m2);
}
Commit	Line	Data
be66cf70	1	/**************************************************************************
	2	* Copyright(c) 2009-2010, ALICE Experiment at CERN, All rights reserved. *
	3	* *
	4	* Author: The ALICE Off-line Project. *
	5	* Contributors are mentioned in the code where appropriate. *
	6	* *
	7	* Permission to use, copy, modify and distribute this software and its *
	8	* documentation strictly for non-commercial purposes is hereby granted *
	9	* without fee, provided that the above copyright notice appears in all *
	10	* copies and that both the copyright notice and this permission notice *
	11	* appear in the supporting documentation. The authors make no claims *
	12	* about the suitability of this software for any purpose. It is *
	13	* provided "as is" without express or implied warranty. *
	14	**************************************************************************/
	15
	16	//////////////////////////////////////////////////////////////////////////
	17	// Afterburner to generate (anti)deuterons simulating coalescence of
	18	// (anti)nucleons as in A. J. Baltz et al., Phys. lett B 325(1994)7.
	19	// If the nucleon generator does not provide a spatial description of
	20	// the source the afterburner can provide one.
	21	//
	22	// There two options for the source: a thermal picture where all nucleons
	23	// are placed randomly and homogeneously in an spherical volume, or
	24	// an expansion one where they are projected onto its surface.
	25	//
	26	// An (anti)deuteron will form if there is a pair of (anti)proton-(anti)neutron
	27	// with momentum difference less than ~ 300MeV and relative distance less than
	28	// ~ 2.1fm. Only 3/4 of these clusters are accepted due to the deuteron spin.
	29	//
	30	// When there are more than one pair fulfilling the coalescence conditions,
	31	// the selected pair can be the one with the first partner, with
	32	// the lowest relative momentum, the lowest relative distance or both.
	33	//////////////////////////////////////////////////////////////////////////
	34
	35	// Author: Eulogio Serradilla <eulogio.serradilla@ciemat.es>,
	36	// Arturo Menchaca <menchaca@fisica.unam.mx>
	37	//
	38
	39	#include "Riostream.h"
	40	#include "TParticle.h"
be66cf70	41	#include "AliStack.h"
95145d47	42	#include "AliRun.h"
be66cf70	43	#include "TMath.h"
	44	#include "TMCProcess.h"
	45	#include "TList.h"
	46	#include "TVector3.h"
	47	#include "AliMC.h"
	48	#include "TArrayF.h"
	49	#include "AliCollisionGeometry.h"
	50	#include "AliGenCocktailEventHeader.h"
	51	#include "AliGenCocktailEntry.h"
	52	#include "AliGenCocktailAfterBurner.h"
	53	#include "AliGenDeuteron.h"
c93255fe	54	#include "AliLog.h"
be66cf70	55
	56	ClassImp(AliGenDeuteron)
	57
	58	AliGenDeuteron::AliGenDeuteron(Int_t sign, Double_t pmax, Double_t rmax, Int_t cluster)
	59	:fSign(1)
	60	,fPmax(pmax)
	61	,fRmax(rmax)
95145d47	62	,fSpinProb(1)
be66cf70	63	,fClusterType(cluster)
	64	,fModel(0)
	65	,fTimeLength(2.5)
	66	,fB(0)
	67	,fR(0)
	68	,fPsiR(0)
	69	,fCurStack(0)
	70	,fNtrk(0)
	71	{
	72	//
	73	// constructor
	74	//
	75	fSign = sign > 0 ? 1:-1;
	76
	77	}
	78
	79	AliGenDeuteron::~AliGenDeuteron()
	80	{
	81	//
	82	// Default destructor
	83	//
	84	}
	85
	86	void AliGenDeuteron::Init()
	87	{
	88	//
	89	// Standard AliGenerator initializer
	90	//
	91	}
	92
	93	void AliGenDeuteron::Generate()
	94	{
	95	//
	96	// Look for coalescence of (anti)nucleons in the nucleon source
	97	// provided by the generator cocktail
	98	//
	99	AliInfo(Form("sign: %d, Pmax: %g GeV/c, Rmax: %g fm, cluster: %d",fSign, fPmax, fRmax, fClusterType));
	100	if(fModel!=kNone) AliInfo(Form("model: %d, time: %g fm/c", fModel, fTimeLength));
	101
	102	AliGenCocktailAfterBurner* gener = (AliGenCocktailAfterBurner*)gAlice->GetMCApp()->Generator();
	103
	104	// find nuclear radius, only for first generator and projectile=target
	105	Bool_t collisionGeometry=0;
	106	if(fModel != kNone && gener->FirstGenerator()->Generator()->ProvidesCollisionGeometry())
	107	{
	108	TString name;
	109	Int_t ap, zp, at, zt;
	110	gener->FirstGenerator()->Generator()->GetProjectile(name,ap,zp);
	111	gener->FirstGenerator()->Generator()->GetTarget(name,at,zt);
	112	if(ap != at) AliWarning("projectile and target have different size");
	113	fR = 1.29*TMath::Power(at, 1./3.);
	114	collisionGeometry = 1;
	115	}
	116
	117	for(Int_t ns = 0; ns < gener->GetNumberOfEvents(); ++ns)
	118	{
	119	gener->SetActiveEventNumber(ns);
	120
	121	if(fModel != kNone && collisionGeometry)
	122	{
	123	fPsiR = (gener->GetCollisionGeometry(ns))->ReactionPlaneAngle();
	124	fB = (gener->GetCollisionGeometry(ns))->ImpactParameter();
	125
	126	if(fB >= 2.*fR) continue; // no collision
127	}
128
be66cf70	129	fCurStack = gener->GetStack(ns);
	130	if(!fCurStack)
	131	{
	132	AliWarning("no event stack");
	133	return;
	134	}
	135
	136	TList* protons = new TList();
	137	protons->SetOwner(kFALSE);
	138	TList* neutrons = new TList();
	139	neutrons->SetOwner(kFALSE);
	140
95145d47	141	// particles produced by the generator
95145d47	142	for (Int_t i=0; i < fCurStack->GetNprimary(); ++i)
be66cf70	143	{
	144	TParticle* iParticle = fCurStack->Particle(i);
	145
95145d47	146	if(iParticle->GetStatusCode() != 1) continue;
be66cf70	147
	148	Int_t pdgCode = iParticle->GetPdgCode();
	149	if(pdgCode == fSign*2212)// (anti)proton
	150	{
	151	FixProductionVertex(iParticle);
	152	protons->Add(iParticle);
	153	}
	154	else if(pdgCode == fSign*2112) // (anti)neutron
	155	{
	156	FixProductionVertex(iParticle);
	157	neutrons->Add(iParticle);
	158	}
	159	}
	160
	161	// look for clusters
	162	if(fClusterType==kFirstPartner)
	163	{
	164	FirstPartner(protons, neutrons);
	165	}
	166	else
	167	{
	168	WeightMatrix(protons, neutrons);
	169	}
	170
	171	protons->Clear("nodelete");
	172	neutrons->Clear("nodelete");
	173
	174	delete protons;
	175	delete neutrons;
	176	}
	177
	178	AliInfo("DONE");
	179	}
	180
	181	Double_t AliGenDeuteron::GetCoalescenceProbability(const TParticle* nucleon1, const TParticle* nucleon2) const
	182	{
	183	//
	184	// Coalescence conditions as in
	185	// A. J. Baltz et al., Phys. lett B 325(1994)7
	186	//
	187	// returns < 0 if coalescence is not possible
	188	// otherwise returns a coalescence probability
	189	//
95145d47	190	const Double_t kProtonMass = 0.938272013;
	191	const Double_t kNeutronMass = 0.939565378;
	192
be66cf70	193	TVector3 v1(nucleon1->Vx(), nucleon1->Vy(), nucleon1->Vz());
	194	TVector3 p1(nucleon1->Px(), nucleon1->Py(), nucleon1->Pz());
	195
	196	TVector3 v2(nucleon2->Vx(), nucleon2->Vy(), nucleon2->Vz());
	197	TVector3 p2(nucleon2->Px(), nucleon2->Py(), nucleon2->Pz());
	198
95145d47	199	Double_t deltaP = 2.*this->GetPcm(p1, kProtonMass, p2, kNeutronMass); // relative momentum in CM frame
95145d47	200	if( deltaP >= fPmax) return -1.;
be66cf70	201
	202	Double_t deltaR = (v2-v1).Mag(); // relative distance (cm)
	203	if(deltaR >= fRmax*1.e-13) return -1.;
	204
	205	if(Rndm() > fSpinProb) return -1.; // spin
	206
	207	if(fClusterType == kLowestMomentum) return 1. - deltaP/fPmax;
	208	if(fClusterType == kLowestDistance) return 1. - 1.e+13*deltaR/fRmax;
	209
	210	return 1. - 1.e+13(deltaPdeltaR)/(fRmax*fPmax);
	211	}
	212
	213	void AliGenDeuteron::FirstPartner(const TList* protons, TList* neutrons)
	214	{
	215	//
	216	// Clusters are made with the first nucleon pair that fulfill
	217	// the coalescence conditions, starting with the protons
	218	//
	219	TIter p_next(protons);
	220	while(TParticle* n0 = (TParticle*) p_next())
	221	{
	222	TParticle* partner = 0;
	223	TIter n_next(neutrons);
	224	while(TParticle* n1 = (TParticle*) n_next() )
	225	{
	226	if(GetCoalescenceProbability(n0, n1) < 0 ) continue; // with next neutron
	227	partner = n1;
	228	break;
	229	}
	230
	231	if(partner == 0) continue; // with next proton
	232
	233	PushDeuteron(n0, partner);
	234
	235	// Remove from the list for the next iteration
	236	neutrons->Remove(partner);
	237	}
	238	}
	239
	240	void AliGenDeuteron::WeightMatrix(const TList* protons, const TList* neutrons)
	241	{
	242	//
	243	// Build all possible nucleon pairs with their own probability
	244	// and select only those with the highest coalescence probability
	245	//
	246	Int_t nMaxPairs = protons->GetSize()*neutrons->GetSize();
	247
	248	TParticle** cProton = new TParticle*[nMaxPairs];
	249	TParticle** cNeutron = new TParticle*[nMaxPairs];
	250	Double_t* cWeight = new Double_t[nMaxPairs];
	251
	252	// build all pairs with probability > 0
	253	Int_t cIdx = -1;
	254	TIter p_next(protons);
	255	while(TParticle* n1 = (TParticle*) p_next())
	256	{
	257	TIter n_next(neutrons);
	258	while(TParticle* n2 = (TParticle*) n_next() )
	259	{
	260	Double_t weight = this->GetCoalescenceProbability(n1,n2);
	261	if(weight < 0) continue;
	262	++cIdx;
	263	cProton[cIdx] = n1;
	264	cNeutron[cIdx] = n2;
265	cWeight[cIdx] = weight;
266	}
267	n_next.Reset();
268	}
269	p_next.Reset();
270
271	Int_t nPairs = cIdx + 1;
272
273	// find the interacting pairs:
274	// remove repeated pairs and select only
275	// the pair with the highest coalescence probability
276
277	Int_t nMaxIntPair = TMath::Min(protons->GetSize(), neutrons->GetSize());
278
279	TParticle** iProton = new TParticle*[nMaxIntPair];
280	TParticle** iNeutron = new TParticle*[nMaxIntPair];
281	Double_t* iWeight = new Double_t[nMaxIntPair];
282
283	Int_t iIdx = -1;
95145d47	284	while(kTRUE)
be66cf70	285	{
	286	Int_t j = -1;
	287	Double_t wMax = 0;
	288	for(Int_t i=0; i < nPairs; ++i)
	289	{
	290	if(cWeight[i] > wMax)
	291	{
	292	wMax=cWeight[i];
	293	j = i;
	294	}
	295	}
	296
	297	if(j == -1 ) break; // end
	298
	299	// Save the interacting pair
	300	++iIdx;
	301	iProton[iIdx] = cProton[j];
	302	iNeutron[iIdx] = cNeutron[j];
	303	iWeight[iIdx] = cWeight[j];
	304
	305	// invalidate all combinations with these pairs for the next iteration
	306	for(Int_t i=0; i < nPairs; ++i)
	307	{
	308	if(cProton[i] == iProton[iIdx]) cWeight[i] = -1.;
	309	if(cNeutron[i] == iNeutron[iIdx]) cWeight[i] = -1.;
	310	}
	311	}
	312
	313	Int_t nIntPairs = iIdx + 1;
	314
	315	delete[] cProton;
	316	delete[] cNeutron;
	317	delete[] cWeight;
	318
	319	// Add the (anti)deuterons to the current event stack
	320	for(Int_t i=0; i<nIntPairs; ++i)
	321	{
	322	TParticle* n1 = iProton[i];
	323	TParticle* n2 = iNeutron[i];
	324	PushDeuteron(n1,n2);
	325	}
	326
	327	delete[] iProton;
	328	delete[] iNeutron;
	329	delete[] iWeight;
	330	}
	331
	332	void AliGenDeuteron::PushDeuteron(TParticle* parent1, TParticle* parent2)
	333	{
	334	//
	335	// Create an (anti)deuteron from parent1 and parent2,
	336	// add to the current stack and set kDoneBit for the parents
	337	//
	338	const Double_t kDeuteronMass = 1.87561282;
	339	const Int_t kDeuteronPdg = 1000010020;
	340
	341	// momentum
	342	TVector3 p1(parent1->Px(), parent1->Py(), parent1->Pz());
	343	TVector3 p2(parent2->Px(), parent2->Py(), parent2->Pz());
	344	TVector3 pN = p1+p2;
	345
	346	// production vertex same as the parent1's
	347	TVector3 vN(parent1->Vx(), parent1->Vy(), parent1->Vz());
	348
349	// E^2 = p^2 + m^2
350	Double_t energy = TMath::Sqrt(pN.Mag2() + kDeuteronMass*kDeuteronMass);
351
352	// Add a new (anti)deuteron to current event stack
0f52fba4	353	fCurStack->PushTrack(1, -1, fSign*kDeuteronPdg,
be66cf70	354	pN.X(), pN.Y(), pN.Z(), energy,
	355	vN.X(), vN.Y(), vN.Z(), parent1->T(),
	356	0., 0., 0., kPNCapture, fNtrk, 1., 0);
	357
	358	// Set kDoneBit for the parents
	359	parent1->SetBit(kDoneBit);
	360	parent2->SetBit(kDoneBit);
	361	}
	362
	363	void AliGenDeuteron::FixProductionVertex(TParticle* i)
	364	{
	365	//
	366	// Replace current generator nucleon spatial distribution
	367	// with a custom distribution according to the selected model
	368	//
	369	if(fModel == kNone \|\| fModel > kExpansion) return;
	370
	371	// semi-axis from collision geometry (fm)
	372	Double_t a = fTimeLength + TMath::Sqrt(fRfR - fBfB/4.);
	373	Double_t b = fTimeLength + fR - fB/2.;
	374	Double_t c = fTimeLength;
	375
	376	Double_t xx = 0;
	377	Double_t yy = 0;
	378	Double_t zz = 0;
	379
	380	if(fModel == kThermal)
	381	{
	382	// uniformly ditributed in the volume on an ellipsoid
	383	// random (r,theta,phi) unit sphere
	384	Double_t r = TMath::Power(Rndm(),1./3.);
	385	Double_t theta = TMath::ACos(2.*Rndm()-1.);
	386	Double_t phi = 2.TMath::Pi()Rndm();
	387
	388	// transform coordenates
	389	xx = arTMath::Sin(theta)*TMath::Cos(phi);
	390	yy = brTMath::Sin(theta)*TMath::Sin(phi);
	391	zz = crTMath::Cos(theta);
	392	}
	393	else if(fModel == kExpansion)
	394	{
	395	// project into the surface of an ellipsoid
	396	xx = aTMath::Sin(i->Theta())TMath::Cos(i->Phi());
	397	yy = bTMath::Sin(i->Theta())TMath::Sin(i->Phi());
	398	zz = c*TMath::Cos(i->Theta());
	399	}
	400
	401	// rotate by the reaction plane angle
	402	Double_t x = xxTMath::Cos(fPsiR)+yyTMath::Sin(fPsiR);
	403	Double_t y = -xxTMath::Sin(fPsiR)+yyTMath::Cos(fPsiR);
	404	Double_t z = zz;
	405
	406	// translate by the production vertex (cm)
	407	i->SetProductionVertex(i->Vx() + 1.e-13x, i->Vy() + 1.e-13y, i->Vz() + 1.e-13*z, i->T());
	408	}
	409
95145d47	410	Double_t AliGenDeuteron::GetS(Double_t p1x, Double_t p1y, Double_t p1z, Double_t m1, Double_t p2x, Double_t p2y, Double_t p2z, Double_t m2) const
	411	{
	412	//
	413	// square of the center of mass energy
	414	//
	415	Double_t E1 = TMath::Sqrt( p1xp1x + p1yp1y + p1zp1z + m1m1);
	416	Double_t E2 = TMath::Sqrt( p2xp2x + p2yp2y + p2zp2z + m2m2);
	417
	418	return (E1+E2)(E1+E2) - ((p1x+p2x)(p1x+p2x) + (p1y+p2y)(p1y+p2y) + (p1z+p2z)(p1z+p2z));
	419	}
	420
	421	Double_t AliGenDeuteron::GetPcm(Double_t p1x, Double_t p1y, Double_t p1z, Double_t m1, Double_t p2x, Double_t p2y, Double_t p2z, Double_t m2) const
	422	{
	423	//
	424	// momentum in the CM frame
	425	//
	426	Double_t s = this->GetS(p1x, p1y, p1z, m1, p2x, p2y, p2z, m2);
	427
	428	return TMath::Sqrt( (s-(m1-m2)(m1-m2))(s-(m1+m2)(m1+m2)) )/(2.TMath::Sqrt(s));
	429	}
	430
	431	Double_t AliGenDeuteron::GetPcm(const TVector3& p1, Double_t m1, const TVector3& p2, Double_t m2) const
	432	{
	433	//
	434	// momentum in the CM frame
	435	//
	436	return this->GetPcm(p1.Px(),p1.Py(),p1.Pz(),m1,p2.Px(),p2.Py(),p2.Pz(),m2);
	437	}
	438