+++ /dev/null
-/**************************************************************************
- * Copyright(c) 1998-1999, 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. *
- **************************************************************************/
-
-/*
-$Log$
-Revision 1.5 2003/01/07 14:11:43 morsch
-Comminication with gray particle model and collision geometry added.
-
-Revision 1.4 2003/01/06 10:09:57 morsch
-Use AliGrayParticleModel.
-
-Revision 1.3 2002/12/02 10:02:40 morsch
-Corrections introduced by F. Silker:
-- SetBetaSource
-- Particle type according to charge.
-
-Revision 1.2 2002/10/14 14:55:35 hristov
-Merging the VirtualMC branch to the main development branch (HEAD)
-
-Revision 1.1.2.1 2002/10/10 16:40:08 hristov
-Updating VirtualMC to v3-09-02
-
-Revision 1.1 2002/10/08 13:53:17 morsch
-Gray particle generator, first commit.
-
-*/
-
-/*
- Generator for gray nucluons in pA interactions.
- Source is modelled by a relativistic Maxwell distributions.
- Original code by Ferenc Sikler <sikler@rmki.kfki.hu>
- */
-
-#include <TDatabasePDG.h>
-#include <TPDGCode.h>
-
-#include "AliCollisionGeometry.h"
-#include "AliGenGrayParticles.h"
-#include "AliGrayParticleModel.h"
-
- ClassImp(AliGenGrayParticles)
-
- AliGenGrayParticles::AliGenGrayParticles():AliGenerator(-1)
-{
-// Default constructor
- fGrayParticleModel = 0;
- fCollisionGeometry = 0;
-}
-
-AliGenGrayParticles::AliGenGrayParticles(Int_t npart)
- :AliGenerator(npart)
-{
-// Constructor
- fName = "GrayParticles";
- fTitle = "Generator for gray particles in pA collisions";
- SetPmax();
- SetTarget();
- SetNominalCmsEnergy();
- SetCharge();
- SetTemperature();
- SetBetaSource();
- fGrayParticleModel = new AliGrayParticleModel();
- fCollisionGeometry = 0;
-}
-
-//____________________________________________________________
-AliGenGrayParticles::~AliGenGrayParticles()
-{
-// Destructor
- delete fGrayParticleModel;
-}
-
-
-void AliGenGrayParticles::Init()
-{
- //
- // Initialization
- //
- Float_t kMass = TDatabasePDG::Instance()->GetParticle(kProton)->Mass();
- fMomentum = fCMS/2. * fZTarget / fATarget;
- fBeta = fMomentum / TMath::Sqrt(kMass * kMass + fMomentum * fMomentum);
-}
-
-
-void AliGenGrayParticles::Generate()
-{
- //
- // Generate one event
- //
- //
- // Communication with Gray Particle Model
- //
- Int_t np, nn;
-
- Float_t b = fCollisionGeometry->ImpactParameter();
- printf("AliGenGrayParticles: Impact parameter from Collision Geometry %f \n", b);
-
- fGrayParticleModel->GetNumberOfGrayNucleons(fCollisionGeometry, np, nn);
-
- //
- Float_t p[3];
- Float_t origin[3] = {0., 0., 0.};
- Float_t polar [3] = {0., 0., 0.};
- Int_t nt, i;
- for(i = 0;i < fNpart; i++) {
- Int_t kf;
- if(fCharge==1) kf = kProton;
- else kf = kNeutron;
- GenerateSlow(fCharge, fTemperature, fBetaSource, p);
-
- SetTrack(fTrackIt, -1, kf, p, origin, polar,
- 0., kPNoProcess, nt, 1.);
-
- KeepTrack(nt);
- }
-}
-
-
-
-
-void AliGenGrayParticles::GenerateSlow(Int_t charge, Double_t T, Double_t beta, Float_t* q)
-/*
- Emit a slow nucleon with "temperature" T [GeV],
- from a source moving with velocity beta
- Three-momentum [GeV/c] is given back in q[3]
-*/
-
-{
- Double_t m, pmax, p, f, theta, phi;
-
- TDatabasePDG * pdg = TDatabasePDG::Instance();
- const Double_t kMassProton = pdg->GetParticle(kProton) ->Mass();
- const Double_t kMassNeutron = pdg->GetParticle(kNeutron)->Mass();
-
- /* Select nucleon type */
- if(charge == 0) m = kMassNeutron;
- else m = kMassProton;
-
- /* Momentum at maximum of Maxwell-distribution */
-
- pmax = TMath::Sqrt(2*T*(T+sqrt(T*T+m*m)));
-
- /* Try until proper momentum */
- /* for lack of primitive function of the Maxwell-distribution */
- /* a brute force trial-accept loop, normalized at pmax */
-
- do
- {
- p = Rndm() * fPmax;
- f = Maxwell(m, p, T) / Maxwell(m , pmax, T);
- }
- while(f < Rndm());
-
- /* Spherical symmetric emission */
- theta = TMath::ACos(2. * Rndm() - 1.);
- phi = 2. * TMath::Pi() * Rndm();
-
- /* Determine momentum components in system of the moving source */
- q[0] = p * TMath::Sin(theta) * TMath::Cos(phi);
- q[1] = p * TMath::Sin(theta) * TMath::Sin(phi);
- q[2] = p * TMath::Cos(theta);
-
- /* Transform to system of the target nucleus */
- /* beta is passed as negative, because the gray nucleons are slowed down */
- Lorentz(m, -beta, q);
-
- /* Transform to laboratory system */
- Lorentz(m, fBeta, q);
-}
-
-Double_t AliGenGrayParticles::Maxwell(Double_t m, Double_t p, Double_t T)
-{
-/* Relativistic Maxwell-distribution */
- Double_t ekin;
- ekin = TMath::Sqrt(p*p+m*m)-m;
- return (p*p * exp(-ekin/T));
-}
-
-
-void AliGenGrayParticles::Lorentz(Double_t m, Double_t beta, Float_t* q)
-{
-/* Lorentz transform in the direction of q[2] */
-
- Double_t gamma = 1/sqrt(1-beta*beta);
- Double_t energy = sqrt(m*m + q[0]*q[0] + q[1]*q[1] + q[2]*q[2]);
- q[2] = gamma * (q[2] + beta*energy);
-}
-
-
-
-
-
-
-
+++ /dev/null
-#ifndef ALIGENGRAYPARTICLES_H
-#define ALIGENGRAYPARTICLES_H
-/* Copyright(c) 198-1999, ALICE Experiment at CERN, All rights reserved. *
- * See cxx source for full Copyright notice */
-
-/* $Id$ */
-
-#include "AliGenerator.h"
-class AliGrayParticleModel;
-
-class AliGenGrayParticles : public AliGenerator
-{
-public:
- AliGenGrayParticles();
- AliGenGrayParticles(Int_t npart);
- virtual ~AliGenGrayParticles();
- virtual void Init();
- virtual void Generate();
- virtual void SetPmax(Float_t pmax = 10.) {fPmax = pmax;}
- virtual void SetNominalCmsEnergy(Float_t energy = 14000.) {fCMS = energy;}
- virtual void SetTarget(Float_t a=208, Float_t z=82) {fATarget = a; fZTarget = z;}
- virtual void SetCharge(Int_t c = 1) {fCharge = c;}
- virtual void SetTemperature(Double_t t = 0.05) {fTemperature = t;}
- virtual void SetBetaSource(Double_t b = 0.05) {fBetaSource = b;}
- //
- virtual void SetGrayParticleModel(AliGrayParticleModel* model)
- {fGrayParticleModel = model;}
- virtual Bool_t NeedsCollisionGeometry() {return kTRUE;}
- virtual void SetCollisionGeometry(AliCollisionGeometry* geom)
- {fCollisionGeometry = geom;}
-
- protected:
- void GenerateSlow(Int_t charge, Double_t T, Double_t beta, Float_t* q);
- Double_t Maxwell(Double_t m, Double_t p, Double_t t);
- void Lorentz(Double_t m, Double_t beta, Float_t* q);
- protected:
- Float_t fCMS; // Center of mass energy
- Float_t fMomentum; // Target nucleus momentum
- Float_t fBeta; // Target nucleus beta
- Float_t fPmax; // Maximum slow nucleon momentum
- Float_t fATarget; // Target nucleus mass number
- Float_t fZTarget; // Target nucleus charge number
- Int_t fCharge; // Slow nucleon charge
- Float_t fTemperature; // Source Temperature
- Float_t fBetaSource; // Source beta
- //
- AliGrayParticleModel* fGrayParticleModel; // The gray particle model
- ClassDef(AliGenGrayParticles,1) // Gray Particle Generator
-};
-#endif
-
-
-
-
-
-