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4 * Author: The ALICE Off-line Project. *
5 * Contributors are mentioned in the code where appropriate. *
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14 **************************************************************************/
18 Revision 1.1 2002/01/08 09:47:28 morsch
19 HIJING parameterisation including baryons, first commit.
22 ///////////////////////////////////////////////////////////////////
23 // Parameterisation of pi, K, n and p eta and pt distributions //
24 // eta: according to HIJING (shadowing + quenching) //
25 // pT : according to CDF measurement at 1.8 TeV //
26 // Author: andreas.morsch@cern.ch //
28 ///////////////////////////////////////////////////////////////////
35 #include "AliGenEventHeader.h"
36 #include "AliGenHIJINGparaBa.h"
39 ClassImp(AliGenHIJINGparaBa)
42 static Double_t ptpi(Double_t *px, Double_t *)
45 // PT-PARAMETERIZATION CDF, PRL 61(88) 1819
46 // POWER LAW FOR PT > 500 MEV
47 // MT SCALING BELOW (T=160 MEV)
49 const Double_t kp0 = 1.3;
50 const Double_t kxn = 8.28;
51 const Double_t kxlim=0.5;
52 const Double_t kt=0.160;
53 const Double_t kxmpi=0.139;
55 Double_t y, y1, xmpi2, ynorm, a;
58 y1=TMath::Power(kp0/(kp0+kxlim),kxn);
60 ynorm=kb*(TMath::Exp(-sqrt(kxlim*kxlim+xmpi2)/kt));
63 y=a*TMath::Power(kp0/(kp0+x),kxn);
65 y=kb*TMath::Exp(-sqrt(x*x+xmpi2)/kt);
69 //_____________________________________________________________________________
70 static Double_t ptscal(Double_t pt, Int_t np)
72 // SCALING EN MASSE PAR RAPPORT A PTPI
73 // MASS PI,K,ETA,RHO,OMEGA,ETA',PHI
74 const Double_t khm[10] = {.13957,.493,.5488,.769,.7826,.958,1.02,0,0,0};
75 // VALUE MESON/PI AT 5 GEV
76 const Double_t kfmax[10]={1.,0.3,0.55,1.0,1.0,1.0,1.0,0,0,0};
78 Double_t f5=TMath::Power(((
79 sqrt(100.018215)+2.)/(sqrt(100.+khm[np]*khm[np])+2.0)),12.3);
80 Double_t fmax2=f5/kfmax[np];
82 Double_t ptpion=100.*ptpi(&pt, (Double_t*) 0);
83 Double_t fmtscal=TMath::Power(((
84 sqrt(pt*pt+0.018215)+2.)/ (sqrt(pt*pt+khm[np]*khm[np])+2.0)),12.3)/
86 return fmtscal*ptpion;
89 //_____________________________________________________________________________
90 static Double_t ptka( Double_t *px, Double_t *)
93 // pt parametrisation for k
99 //_____________________________________________________________________________
100 static Double_t etapic( Double_t *py, Double_t *)
103 // eta parametrisation for pi
105 const Double_t ka1 = 4913.;
106 const Double_t ka2 = 1819.;
107 const Double_t keta1 = 0.22;
108 const Double_t keta2 = 3.66;
109 const Double_t kdeta1 = 1.47;
110 const Double_t kdeta2 = 1.51;
111 Double_t y=TMath::Abs(*py);
113 Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
114 Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
115 return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
118 //_____________________________________________________________________________
119 static Double_t etakac( Double_t *py, Double_t *)
122 // eta parametrisation for ka
124 const Double_t ka1 = 497.6;
125 const Double_t ka2 = 215.6;
126 const Double_t keta1 = 0.79;
127 const Double_t keta2 = 4.09;
128 const Double_t kdeta1 = 1.54;
129 const Double_t kdeta2 = 1.40;
130 Double_t y=TMath::Abs(*py);
132 Double_t ex1 = (y-keta1)*(y-keta1)/(2*kdeta1*kdeta1);
133 Double_t ex2 = (y-keta2)*(y-keta2)/(2*kdeta2*kdeta2);
134 return ka1*TMath::Exp(-ex1)+ka2*TMath::Exp(-ex2);
137 static Double_t ptbaryon( Double_t *px, Double_t *)
141 //____________________________________________________________
143 return ptscal(*px,7); // 7==> Baryon in the PtScal function
146 static Double_t etabaryon( Double_t *py, Double_t *)
149 //____________________________________________________________
150 const Float_t p0 = 1.10343e+02;
151 const Float_t p1 = 1.73247e+01;
152 const Float_t p2 = -7.23808e+00;
153 const Float_t p3 = 4.48334e-01;
154 const Double_t y = TMath::Abs(*py);
156 return (p0+p1*y+p2*y*y+p3*y*y*y)/20.;
159 AliGenHIJINGparaBa::AliGenHIJINGparaBa()
163 // Default constructor
165 fName="HIGINGparaBa";
166 fTitle="HIJING Parametrisation Particle Generator with Baryons";
171 //_____________________________________________________________________________
172 AliGenHIJINGparaBa::AliGenHIJINGparaBa(Int_t npart)
173 :AliGenHIJINGpara(npart)
176 // Standard constructor
178 fName="HIGINGparaBa";
179 fTitle="HIJING Parametrisation Particle Generator with Baryons";
184 //_____________________________________________________________________________
185 AliGenHIJINGparaBa::~AliGenHIJINGparaBa()
188 // Standard destructor
194 //_____________________________________________________________________________
195 void AliGenHIJINGparaBa::Init()
198 // Initialise the HIJING parametrisation
200 Float_t etaMin =-TMath::Log(TMath::Tan(
201 TMath::Min((Double_t)fThetaMax/2,TMath::Pi()/2-1.e-10)));
202 Float_t etaMax = -TMath::Log(TMath::Tan(
203 TMath::Max((Double_t)fThetaMin/2,1.e-10)));
204 fPtpi = new TF1("ptpi",&ptpi,0,20,0);
205 fPtka = new TF1("ptka",&ptka,0,20,0);
206 fPtba = new TF1("ptbaryon",&ptbaryon,0,20,0);
207 fETApic = new TF1("etapic",&etapic,etaMin,etaMax,0);
208 fETAkac = new TF1("etakac",&etakac,etaMin,etaMax,0);
209 fETAba = new TF1("etabaryon",&etabaryon,etaMin,etaMax,0);
211 TF1 *etaPic0 = new TF1("etapic",&etapic, -7, 7, 0);
212 TF1 *etaKac0 = new TF1("etakac",&etakac, -7, 7, 0);
213 TF1 *etaBar0 = new TF1("etabar",&etabaryon, -7, 7, 0);
215 TF1 *ptPic0 = new TF1("ptpi", &ptpi, 0., 15., 0);
216 TF1 *ptKac0 = new TF1("ptka", &ptka, 0., 15., 0);
217 TF1 *ptBar0 = new TF1("ptbar", &ptbaryon, 0., 15., 0);
219 Float_t intETApi = etaPic0->Integral(-0.5, 0.5);
220 Float_t intETAka = etaKac0->Integral(-0.5, 0.5);
221 Float_t intETAba = etaBar0->Integral(-0.5, 0.5);
223 Float_t scalePi = 6979./(intETApi/1.5);
224 Float_t scaleKa = 657./(intETAka/2.0);
225 Float_t scaleBa = 364./(intETAba/2.0);
227 // Fraction of events corresponding to the selected pt-range
228 Float_t intPt = (0.837*ptPic0->Integral(0, 15)+
229 0.105*ptKac0->Integral(0, 15)+
230 0.058*ptBar0->Integral(0, 15));
231 Float_t intPtSel = (0.837*ptPic0->Integral(fPtMin, fPtMax)+
232 0.105*ptKac0->Integral(fPtMin, fPtMax)+
233 0.058*ptBar0->Integral(fPtMin, fPtMax));
234 Float_t ptFrac = intPtSel/intPt;
236 // Fraction of events corresponding to the selected eta-range
237 Float_t intETASel = (scalePi*etaPic0->Integral(etaMin, etaMax)+
238 scaleKa*etaKac0->Integral(etaMin, etaMax)+
239 scaleBa*etaBar0->Integral(etaMin, etaMax));
240 // Fraction of events corresponding to the selected phi-range
241 Float_t phiFrac = (fPhiMax-fPhiMin)/2/TMath::Pi();
243 fParentWeight = Float_t(fNpart)/(intETASel*ptFrac*phiFrac);
245 printf("%s: The number of particles in the selected kinematic region corresponds to %f percent of a full event \n",
246 ClassName(),100.*fParentWeight);
248 // Issue warning message if etaMin or etaMax are outside the alowed range
249 // of the parametrization
250 if (etaMin < -8.001 || etaMax > 8.001) {
251 printf("\n \n WARNING FROM AliGenHIJINGParaBa !");
252 printf("\n YOU ARE USING THE PARAMETERISATION OUTSIDE ");
253 printf("\n THE ALLOWED PSEUDORAPIDITY RANGE (-8. - 8.)");
254 printf("\n YOUR LIMITS: %f %f \n \n ", etaMin, etaMax);
258 //_____________________________________________________________________________
259 void AliGenHIJINGparaBa::Generate()
262 // Generate one trigger
266 const Float_t kBorne1 = 0.837;
267 const Float_t kBorne2 = kBorne1+0.105;
269 Float_t polar[3]= {0,0,0};
271 const Int_t kPions[3] = {kPi0, kPiPlus, kPiMinus};
272 const Int_t kKaons[4] = {kK0Long, kK0Short, kKPlus, kKMinus};
273 const Int_t kBaryons[4] = {kProton, kProtonBar, kNeutron, kNeutronBar};
276 Float_t pt, pl, ptot;
279 Int_t i, part, nt, j;
286 for (j=0;j<3;j++) origin[j]=fOrigin[j];
288 if(fVertexSmear == kPerEvent) {
291 while(TMath::Abs(dv[2]) > fCutVertexZ*fOsigma[2]) {
293 for (j=0; j < 3; j++) {
294 dv[j] = fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
295 TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
298 for (j=0; j < 3; j++) origin[j] += dv[j];
302 eventVertex[0] = origin[0];
303 eventVertex[1] = origin[1];
304 eventVertex[2] = origin[2];
306 for(i=0;i<fNpart;i++) {
309 if(random[0] < kBorne1) {
310 part = kPions[Int_t (random[1]*3)];
313 } else if (random[0] < kBorne2) {
314 part = kKaons[Int_t (random[1]*4)];
318 part = kBaryons[Int_t (random[1]*4)];
323 phi=fPhiMin+random[2]*(fPhiMax-fPhiMin);
324 theta=2*TMath::ATan(TMath::Exp(-etaf->GetRandom()));
325 if(theta<fThetaMin || theta>fThetaMax) continue;
327 pl=pt/TMath::Tan(theta);
328 ptot=TMath::Sqrt(pt*pt+pl*pl);
329 if(ptot<fPMin || ptot>fPMax) continue;
330 p[0]=pt*TMath::Cos(phi);
331 p[1]=pt*TMath::Sin(phi);
333 if(fVertexSmear==kPerTrack) {
336 origin[j]=fOrigin[j]+fOsigma[j]*TMath::Cos(2*random[2*j]*TMath::Pi())*
337 TMath::Sqrt(-2*TMath::Log(random[2*j+1]));
340 SetTrack(fTrackIt,-1,part,p,origin,polar,0,kPPrimary,nt,fParentWeight);
345 AliGenEventHeader* header = new AliGenEventHeader("HIJINGparam");
347 header->SetPrimaryVertex(eventVertex);
348 gAlice->SetGenEventHeader(header);