1 /**************************************************************************
2 * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. *
4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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8 * documentation strictly for non-commercial purposes is hereby granted *
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12 * about the suitability of this software for any purpose. It is *
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14 **************************************************************************/
19 // Realisation of AliLhcProcess for the fast simulation of the
20 // Intra Beam Scattering process
21 // in transverse and longitudinal direction.
22 // Author: Andreas Morsch
23 // andreas.morsch@cern.ch
26 #include "AliLhcProcessIBS.h"
28 #include "AliLhcIRegion.h"
29 #include "AliLhcBeam.h"
35 #include <TMultiGraph.h>
37 ClassImp(AliLhcProcessIBS)
39 Double_t func(Double_t *x, Double_t *par);
41 AliLhcProcessIBS::AliLhcProcessIBS(AliLHC* lhc, const char* name, const char* title)
42 :AliLhcProcess(lhc,name,title),
53 AliLhcProcessIBS::AliLhcProcessIBS(const AliLhcProcessIBS& ibs):
66 AliLhcProcessIBS::~AliLhcProcessIBS()
72 void AliLhcProcessIBS::Init()
75 const Float_t r0=1.535e-16;
77 printf("\n Initializing Process %s", GetName());
78 printf("\n ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^");
80 fIRegions = fAccelerator->IRegions();
82 for (Int_t i = 0; i < 2; i++) {
83 fBeam[i] = fAccelerator->Beam(i);
84 fR[i] = r0*fBeam[i]->Z()*fBeam[i]->Z()/fBeam[i]->A();
85 fE[i] = 0.938*fBeam[i]->A();
89 void AliLhcProcessIBS::Evolve(Float_t dt)
92 // Evolve by one time step dt
93 printf("\n Here process %s %f:", GetName(), dt);
94 for (Int_t i=0; i<2; i++) {
96 Float_t sige = fBeam[i]->EnergySpread();
97 Float_t avbeta = fAccelerator->AverageBeta();
98 Float_t avd = fAccelerator->AverageDisp();
100 Float_t gamma = fBeam[i]->Gamma();
101 Float_t epsx = fBeam[i]->Emittance()*gamma;
103 Float_t epse = fBeam[i]->LongEmittance();
104 Float_t sigxb = TMath::Sqrt(epsx/gamma*avbeta);
105 Float_t sigx = TMath::Sqrt(sigxb*sigxb+(avd*avd*sige*sige));
106 Float_t ssigx = TMath::Sqrt(epsx/gamma/avbeta);
108 Float_t ssigy = ssigx;
110 Float_t asd = fBeam[i]->N()*fR[i]*fR[i]*fE[i]/
111 (16.*TMath::Pi()*gamma*epsx*epsy*epse);
114 Float_t d = sige*avd/sigx;
116 Float_t at = sige*TMath::Sqrt(1.-d*d)/(gamma*ssigx);
117 Float_t bt = sige*TMath::Sqrt(1.-d*d)/(gamma*ssigy);
118 Float_t ct = sige*TMath::Sqrt(1.-d*d)*TMath::Sqrt(4.*sigy/fR[i]);
124 TF1 *fct = new TF1("func",func, 0., 1., 3);
126 Float_t f = (Float_t) 8.0*TMath::Pi()*
127 fct->Integral(0., 1., par, 1.e-5);
129 fTaux = 1./(asd*f*(d*d-at*at/2.));
130 fTaue = 1./(asd*f*(1.-d*d));
131 // printf("\n taux, taue %f %f", taux, taue);
132 // Float_t tauy = -2./at*at/asd/f;
133 fBeam[i]->IncreaseEmittance(dt/fTaux, dt/fTaue);
138 void AliLhcProcessIBS::SetMonitor(Int_t n)
140 // Initialize Monitor
141 if (fTauxArray) delete fTauxArray;
142 if (fTaueArray) delete fTaueArray;
143 fTauxArray = new Float_t[n];
144 fTaueArray = new Float_t[n];
148 void AliLhcProcessIBS::Record()
150 // Record monitor quantities
151 fTauxArray[fAccelerator->Nt()] = fTaux/3600.;
152 fTaueArray[fAccelerator->Nt()] = fTaue/3600.;
156 void AliLhcProcessIBS::DrawPlots()
158 // Draw monitor plots
159 Float_t* t = fAccelerator->TimeA();
161 TH1 *t1 = new TH1F("t1","Hor. IBS growth time",fNmax,0,t[fNmax]);
163 t1->SetMaximum(fTauxArray[fNmax]*1.1);
165 t1->GetXaxis()->SetTitle("t (h)");
166 t1->GetYaxis()->SetTitle("tau_x (t)");
168 TH1 *t2 = new TH1F("t2","Long. IBS growth time",fNmax,0,t[fNmax]);
170 t2->SetMaximum(fTaueArray[fNmax]*1.1);
172 t2->GetXaxis()->SetTitle("t (h)");
173 t2->GetYaxis()->SetTitle("tau_l (t)");
175 TGraph* grTaux = new TGraph(fNmax, fAccelerator->TimeA(), fTauxArray);
176 grTaux->SetHistogram(t1);
178 TGraph* grTaue = new TGraph(fNmax, fAccelerator->TimeA(), fTaueArray);
179 grTaue->SetHistogram(t2);
180 grTaue->SetLineStyle(2);
182 TMultiGraph* mg = new TMultiGraph();
186 TCanvas *c3 = new TCanvas("c3","IBS", 200, 10, 700, 500);
189 mg->GetXaxis()->SetTitle("t (h)");
190 mg->GetYaxis()->SetTitle("IBS Growth Time (h)");
198 AliLhcProcessIBS& AliLhcProcessIBS::operator=(const AliLhcProcessIBS & /*rhs*/)
200 // Assignment operator
204 Double_t func(Double_t *x, Double_t *par)
208 Double_t cc = par[2];
210 const Double_t kbc = 0.5772;
214 Double_t p=1.0/TMath::Sqrt(x2+a*a*x1);
215 Double_t q=1.0/TMath::Sqrt(x2+b*b*x1);
216 return (1.0-3.0*x2)*p*q*(2.0*TMath::Log(0.5*cc*(p+q))-kbc);