PamVMC/src/PamVMCPrimaryGenerator.cxx

// $Id: PamVMCPrimaryGenerator.cxx,v 1.0 2006/06/03 


#include <TVirtualMC.h>
#include <TVirtualMCStack.h>
#include <TPDGCode.h>
#include <TDatabasePDG.h>
#include <TParticlePDG.h>
#include <TVector3.h>
#include <TMath.h>
#include <Riostream.h>

#include "PamVMCPrimaryGenerator.h"

using namespace TMath;

ClassImp(PamVMCPrimary)

PamVMCPrimary & operator+=(PamVMCPrimary &a, const PamVMCPrimary &b)
{
  a.fPDG=b.fPDG;
  a.fX0=b.fX0;
  a.fY0=b.fY0;
  a.fZ0=b.fZ0;
  a.fTHETA=b.fTHETA;
  a.fPHI=b.fPHI;
  a.fP0=b.fP0;
  a.fGOOD=b.fGOOD;

  return a;
}


ClassImp(PamVMCPrimaryGenerator)

PamVMCPrimaryGenerator::PamVMCPrimaryGenerator(TVirtualMCStack* stack) 
  : TObject(),
    fStack(stack),
    fevno(0),
    fmass(0.),
    fcharge(0.),
    frandom(0)
{
// Standard constructor

  ftheta = new TF1("ftheta","sin(x)*cos(x)",0.,acos(-1.)/4.);
  ftheta->SetNpx(1000);

  fprimColl = new TClonesArray("PamVMCPrimary");
  fprim.fPDG=kProton;
  fprim.fX0=1.;
  fprim.fY0=1.;
  fprim.fZ0=130.;
  fprim.fTHETA=0.;
  fprim.fPHI=0.;
  fprim.fP0=1.; //1GV

} 

PamVMCPrimaryGenerator::PamVMCPrimaryGenerator()
  : TObject(),
    fStack(0),
    fevno(0),
    fmass(0.),
    fcharge(0.),
    fprimColl(0),
    frandom(0)
{    
 // Default constructor
  //Default primary proton
  ftheta = new TF1("ftheta","sin(x)*cos(x)",0.,acos(-1.)/4.);
  ftheta->SetNpx(1000);

  fprim.fPDG=kProton;
  fprim.fX0=1.;
  fprim.fY0=1.;
  fprim.fZ0=130.;
  fprim.fTHETA=0.;
  fprim.fPHI=0.;
  fprim.fP0=1.; //1GV
}

PamVMCPrimaryGenerator::~PamVMCPrimaryGenerator() 
{
// Destructor
  delete ftheta;
  delete fprimColl;
}

// private methods


void PamVMCPrimaryGenerator::GeneratePrimary()
{    
// Add one primary particle to the user stack (derived from TVirtualMCStack).
  
  // Track ID (filled by stack)
  Int_t ntr;
 
  // Option: to be tracked
  Int_t toBeDone = 1; 
 
  // Particle type
  Int_t pdg  = fprim.fPDG;
  
  Double_t fvx, fvy, fvz;
  fvx=fprim.fX0;
  fvy=fprim.fY0;
  fvz=fprim.fZ0;

  // Position
  
  Double_t tof = 0.;

  // Energy (in GeV)
  //printf("generateprimary check fprimP0 = %f\n",fprim.fP0);
  Double_t kinEnergy = MomentumToKinE(fprim.fP0);     
  Double_t e  = fmass + kinEnergy;
 
  // Particle momentum
  Double_t  px, py, pz;
   
  px = fprim.fP0*Sin(fprim.fTHETA)*Cos(fprim.fPHI);
  py = fprim.fP0*Sin(fprim.fTHETA)*Sin(fprim.fPHI);
  pz = -fprim.fP0*Cos(fprim.fTHETA);
 
  // Polarization
  TVector3 polar;

  // Add particle to stack 
  fStack->PushTrack(toBeDone, -1, pdg, px, py, pz, e, fvx, fvy, fvz, tof, 
                   polar.X(), polar.Y(), polar.Z(), 
                   kPPrimary, ntr, 1., 0);

  PamVMCPrimary * pc = (PamVMCPrimary *)fprimColl->New(fevno++);
 
  *pc = fprim;
}


void PamVMCPrimaryGenerator::SetParticle(Int_t pdg){
  fprim.fPDG=pdg;
  //TParticlePDG* particlePDG = TDatabasePDG::Instance()->GetParticle(fprim.fPDG);
  fmass = (TDatabasePDG::Instance()->GetParticle(fprim.fPDG))->Mass();
  fcharge = ((TDatabasePDG::Instance()->GetParticle(fprim.fPDG))->Charge())/3.;
}

void PamVMCPrimaryGenerator::SetMomentum(
                              Double_t px, Double_t py, Double_t pz) 
{
  fprim.fP0= Sqrt(px*px+py*py+pz*pz);
  fprim.fTHETA=ATan(Sqrt(px*px+py*py)/pz);
  fprim.fPHI=ATan(py/px);
}
                                     
void PamVMCPrimaryGenerator::GenSpe(Double_t PEmin, Double_t PEmax, Bool_t isEnergy)
{
  if(isEnergy) {
    fprim.fP0=frandom->Uniform(KinEToMomentum(PEmin),KinEToMomentum(PEmax));
  } else{
    fprim.fP0=frandom->Uniform(PEmin,PEmax);
  }

}

void PamVMCPrimaryGenerator::GenSpe(Double_t PEmin, Double_t PEmax, Double_t gamma, Bool_t isEnergy)
{
  Double_t alpha = 1.+gamma; //integral spectral index
  if(alpha==0.){
    fprim.fP0=Exp(Log(PEmin)+frandom->Uniform(0.,1.)*(Log(PEmax)-Log(PEmin)));
  } else {
    if(PEmin==0.) PEmin=1.E-10;
    fprim.fP0=Power((frandom->Uniform(0.,1.)*(Power(PEmax,alpha)-Power(PEmin,alpha))+Power(PEmin,alpha)),1./alpha);
  }
  cout<<"GenSpe fprim.fP0= "<<fprim.fP0<<endl;
  if(isEnergy) fprim.fP0=KinEToMomentum(fprim.fP0);

}


//Cecilia Pizzolotto: powerlaw spectrum 3 with the shape
// J(E) = 0.5*(E + b * exp(-c * sqrt(E)))^-a
// between PEmin and PEmax and with the input parameters a,b,c.
// Valeria di Felice fits parameter values are:
// protons:   a,b,c= 2.70, 2.15, 0.21
// electrons: a,b,c= 0.0638, 1.248e-16, -38.248  
void PamVMCPrimaryGenerator::GenSpe_3par(Double_t PEmin, Double_t PEmax, Double_t a, Double_t b, Double_t c)
{

  Bool_t found=0;
  Double_t funct_min, funct_max;
  funct_max = function3par(PEmin,a,b,c);
  funct_min = function3par(PEmax,a,b,c);
  //
  Double_t wurfP;
  Double_t wurfy ;
  //printf("in genspe3par^^^^%f ^^%f ^^^^^^^^%f ^^^^^%f^^^^^^^\n",PEmin,PEmax,funct_min,funct_max);
  //printf("in par^^ %f  %f  %f \n",a,b,c);
  while( found==0 )
    {
      wurfP = frandom->Uniform(PEmin,PEmax);
      wurfy = frandom->Uniform(funct_min,funct_max);
      if( wurfy<(function3par(wurfP,a,b,c) )) 
        {
          // this is ok!
          fprim.fP0=wurfP;
          found=1;
        }
    }
  //printf("exit+++++++++++++++++++  %f   %f \n",wurfP,fprim.fP0);
}


// cecilia pizzolotto
void PamVMCPrimaryGenerator::GenSpe_Flat(Double_t PEmin, Double_t PEmax, Double_t gamma, Bool_t isEnergy)
{
  // Generates a flat spectrum from PEmin to PElim. Then a power law
  Double_t PElim = 1.;
  //Double_t alpha = 1.+gamma; //integral spectral index

  Bool_t   okflag=0.;
  Double_t throw_x =0.;
  Double_t throw_y =0.;
  
  while(okflag==0)
    {
      throw_x=frandom->Uniform(PEmin,PEmax);
      //        cout<<"        x "<<throw_x<<endl;
      if(throw_x<=PElim)
        {
          okflag=1.;
        }
      else
        {
          throw_y=frandom->Uniform(0.,1.);
          if( throw_y<(1*pow(throw_x,gamma)))
            {
              okflag=1.;
            }
        }
    }
  fprim.fP0=throw_x;
  //h->Fill(fprimf.P0);
  okflag=0.; // reset
  
  if(isEnergy) fprim.fP0=KinEToMomentum(fprim.fP0);

}

// Spherical distribution -- Test by Cecilia P july 2009 ----
// flusso isotropo su 2pi
void PamVMCPrimaryGenerator::GenSphericalPhiThe()
{
  // Generate phi theta
  Double_t theta=0.;
  Double_t phi=0.;
  
  Double_t xcos = sqrt( frandom->Uniform(0.,1.) );
  theta = acos(xcos);   //RAD
  
  phi = frandom->Uniform(0.,2.*Pi());
  
  SetDirection(theta, phi);
  return;
}


void PamVMCPrimaryGenerator::GenSphPhiThe(Double_t xmin, Double_t xmax, Double_t ymin, Double_t ymax, 
                                          Double_t zmin, Double_t zmax)
{
  Bool_t trkGood = kFALSE;
  Double_t theta = 999.;
  Double_t phi = 0.;
  Double_t x2,y2,x3,y3;
  Double_t x0,y0,z0;

  //static const Double_t rad2deg = 57.2958;
  // S21 and S31 position/size taken as reference (z on top of det)
  // constraint: must pass throuth these planes
  static const Double_t s2_xmax=9.05, s2_ymax=7.55, s2_z=73.439; // z on top of det
  static const Double_t s3_xmax=9.05, s3_ymax=7.55, s3_z=26.093; // z on top of det

  //Double_t thetamax=3.14;
  //thetamax = atan((xmax+s3_xmax)/(zmax-s3_z));
  //cout<<" Quanto è il theta max? "<<thetamax<<" in deg "<<thetamax*(90./Pi())<<endl;

  while (trkGood!=kTRUE)
    {
       x0= frandom->Uniform(xmin,xmax);
       y0= frandom->Uniform(ymin,ymax);
       z0= frandom->Uniform(zmin,zmax);
  
      // Generate phi theta
      theta=999.; // init
      while (theta>=0.65) // take only theta smaller than 37deg=0.65rad
        {
          Double_t xcos = sqrt( frandom->Uniform(0.,1.) );
          theta = acos(xcos);   //RAD
        }
      phi = frandom->Uniform(0.,2.*Pi());
 
      // Calculate xy at the constraint
      Double_t fact2 = (s2_z-z0)/cos(theta);
      x2 = x0 + fabs(fact2) *  sin(theta) * cos(phi);
      y2 = y0 + fabs(fact2) *  sin(theta) * sin(phi);
      Double_t fact3 = (s3_z-z0)/cos(theta);
      x3 = x0 + fabs(fact3) *  sin(theta) * cos(phi);
      y3 = y0 + fabs(fact3) *  sin(theta) * sin(phi);
         
      //cout<<" x/y0= "<<x0<<" "<<y0<<"  x/y2= "<<fact2*sin(theta)*cos(phi)<<" "<<x2<<"  xy3= "<<
      //  fact3*sin(theta)*cos(phi)<<" "<<x3<<"   phi/the "<<phi*(90./Pi())<<" "<<theta*(90./Pi())<<endl;

      // Test condition on the direction
      if ( Abs(x2) <= Abs(s2_xmax) && Abs(y2) <= Abs(s2_ymax) &&
           Abs(x3) <= Abs(s3_xmax) && Abs(y3) <= Abs(s3_ymax) ) {
        trkGood = kTRUE;
        //cout<<" x/y0= "<<x0<<" "<<y0<<"  x/y2= "<<fact2*sin(theta)*cos(phi)<<" "<<x2<<"  xy3= "<<
        //  fact3*sin(theta)*cos(phi)<<" "<<x3<<endl;
      }      
    } 

  // Set direction and position:
  SetDirection(theta, phi);
  SetPosition(x0, y0, z0);
  
  return;
}
1	nikolas	1.1	// $Id: PamVMCPrimaryGenerator.cxx,v 1.0 2006/06/03
2	nikolas	1.2
3	nikolas	1.1
4			#include <TVirtualMC.h>
5			#include <TVirtualMCStack.h>
6			#include <TPDGCode.h>
7			#include <TDatabasePDG.h>
8			#include <TParticlePDG.h>
9			#include <TVector3.h>
10			#include <TMath.h>
11	pam-rm2	1.5	#include <Riostream.h>
12	nikolas	1.1
13			#include "PamVMCPrimaryGenerator.h"
14
15	pam-rm2	1.5	using namespace TMath;
16	nikolas	1.2
17			ClassImp(PamVMCPrimary)
18
19			PamVMCPrimary & operator+=(PamVMCPrimary &a, const PamVMCPrimary &b)
20			{
21			a.fPDG=b.fPDG;
22			a.fX0=b.fX0;
23			a.fY0=b.fY0;
24			a.fZ0=b.fZ0;
25			a.fTHETA=b.fTHETA;
26			a.fPHI=b.fPHI;
27			a.fP0=b.fP0;
28			a.fGOOD=b.fGOOD;
29
30			return a;
31			}
32
33
34	nikolas	1.1	ClassImp(PamVMCPrimaryGenerator)
35
36			PamVMCPrimaryGenerator::PamVMCPrimaryGenerator(TVirtualMCStack* stack)
37			: TObject(),
38			fStack(stack),
39	nikolas	1.2	fevno(0),
40			fmass(0.),
41			fcharge(0.),
42	pam-rm2	1.5	frandom(0)
43	nikolas	1.1	{
44			// Standard constructor
45	pam-rm2	1.5
46			ftheta = new TF1("ftheta","sin(x)*cos(x)",0.,acos(-1.)/4.);
47			ftheta->SetNpx(1000);
48
49	nikolas	1.2	fprimColl = new TClonesArray("PamVMCPrimary");
50			fprim.fPDG=kProton;
51			fprim.fX0=1.;
52			fprim.fY0=1.;
53			fprim.fZ0=130.;
54			fprim.fTHETA=0.;
55			fprim.fPHI=0.;
56			fprim.fP0=1.; //1GV
57	nikolas	1.1
58	nikolas	1.2	}
59	nikolas	1.1
60			PamVMCPrimaryGenerator::PamVMCPrimaryGenerator()
61			: TObject(),
62			fStack(0),
63	nikolas	1.2	fevno(0),
64			fmass(0.),
65			fcharge(0.),
66			fprimColl(0),
67	pam-rm2	1.5	frandom(0)
68	nikolas	1.1	{
69	pam-rm2	1.5	// Default constructor
70	nikolas	1.2	//Default primary proton
71	pam-rm2	1.5	ftheta = new TF1("ftheta","sin(x)*cos(x)",0.,acos(-1.)/4.);
72			ftheta->SetNpx(1000);
73
74	nikolas	1.2	fprim.fPDG=kProton;
75			fprim.fX0=1.;
76			fprim.fY0=1.;
77			fprim.fZ0=130.;
78			fprim.fTHETA=0.;
79			fprim.fPHI=0.;
80			fprim.fP0=1.; //1GV
81	nikolas	1.1	}
82
83			PamVMCPrimaryGenerator::~PamVMCPrimaryGenerator()
84			{
85	nikolas	1.2	// Destructor
86	pam-rm2	1.5	delete ftheta;
87	nikolas	1.2	delete fprimColl;
88	nikolas	1.1	}
89
90			// private methods
91
92
93			void PamVMCPrimaryGenerator::GeneratePrimary()
94			{
95			// Add one primary particle to the user stack (derived from TVirtualMCStack).
96
97			// Track ID (filled by stack)
98			Int_t ntr;
99
100			// Option: to be tracked
101			Int_t toBeDone = 1;
102
103			// Particle type
104	nikolas	1.2	Int_t pdg = fprim.fPDG;
105
106			Double_t fvx, fvy, fvz;
107			fvx=fprim.fX0;
108			fvy=fprim.fY0;
109			fvz=fprim.fZ0;
110
111	nikolas	1.1	// Position
112	nikolas	1.2
113	nikolas	1.1	Double_t tof = 0.;
114
115			// Energy (in GeV)
116	pizzolot	1.6	//printf("generateprimary check fprimP0 = %f\n",fprim.fP0);
117	nikolas	1.2	Double_t kinEnergy = MomentumToKinE(fprim.fP0);
118			Double_t e = fmass + kinEnergy;
119	nikolas	1.1
120			// Particle momentum
121	nikolas	1.2	Double_t px, py, pz;
122
123			px = fprim.fP0Sin(fprim.fTHETA)Cos(fprim.fPHI);
124			py = fprim.fP0Sin(fprim.fTHETA)Sin(fprim.fPHI);
125			pz = -fprim.fP0*Cos(fprim.fTHETA);
126	nikolas	1.1
127			// Polarization
128			TVector3 polar;
129
130			// Add particle to stack
131	nikolas	1.2	fStack->PushTrack(toBeDone, -1, pdg, px, py, pz, e, fvx, fvy, fvz, tof,
132	nikolas	1.1	polar.X(), polar.Y(), polar.Z(),
133			kPPrimary, ntr, 1., 0);
134	nikolas	1.2
135			PamVMCPrimary * pc = (PamVMCPrimary *)fprimColl->New(fevno++);
136
137			*pc = fprim;
138	nikolas	1.1	}
139
140
141	nikolas	1.2	void PamVMCPrimaryGenerator::SetParticle(Int_t pdg){
142			fprim.fPDG=pdg;
143			//TParticlePDG* particlePDG = TDatabasePDG::Instance()->GetParticle(fprim.fPDG);
144			fmass = (TDatabasePDG::Instance()->GetParticle(fprim.fPDG))->Mass();
145			fcharge = ((TDatabasePDG::Instance()->GetParticle(fprim.fPDG))->Charge())/3.;
146			}
147	nikolas	1.1
148	nikolas	1.2	void PamVMCPrimaryGenerator::SetMomentum(
149			Double_t px, Double_t py, Double_t pz)
150			{
151			fprim.fP0= Sqrt(pxpx+pypy+pz*pz);
152			fprim.fTHETA=ATan(Sqrt(pxpx+pypy)/pz);
153			fprim.fPHI=ATan(py/px);
154	nikolas	1.1	}
155	nikolas	1.2
156			void PamVMCPrimaryGenerator::GenSpe(Double_t PEmin, Double_t PEmax, Bool_t isEnergy)
157			{
158			if(isEnergy) {
159	pam-rm2	1.5	fprim.fP0=frandom->Uniform(KinEToMomentum(PEmin),KinEToMomentum(PEmax));
160	nikolas	1.2	} else{
161	pam-rm2	1.5	fprim.fP0=frandom->Uniform(PEmin,PEmax);
162	nikolas	1.2	}
163	nikolas	1.1
164	nikolas	1.2	}
165	nikolas	1.1
166	nikolas	1.2	void PamVMCPrimaryGenerator::GenSpe(Double_t PEmin, Double_t PEmax, Double_t gamma, Bool_t isEnergy)
167			{
168			Double_t alpha = 1.+gamma; //integral spectral index
169			if(alpha==0.){
170	pam-rm2	1.5	fprim.fP0=Exp(Log(PEmin)+frandom->Uniform(0.,1.)*(Log(PEmax)-Log(PEmin)));
171	nikolas	1.2	} else {
172			if(PEmin==0.) PEmin=1.E-10;
173	pam-rm2	1.5	fprim.fP0=Power((frandom->Uniform(0.,1.)*(Power(PEmax,alpha)-Power(PEmin,alpha))+Power(PEmin,alpha)),1./alpha);
174	nikolas	1.2	}
175	pizzolot	1.6	cout<<"GenSpe fprim.fP0= "<<fprim.fP0<<endl;
176			if(isEnergy) fprim.fP0=KinEToMomentum(fprim.fP0);
177
178			}
179
180
181			//Cecilia Pizzolotto: powerlaw spectrum 3 with the shape
182			// J(E) = 0.5(E + b exp(-c * sqrt(E)))^-a
183			// between PEmin and PEmax and with the input parameters a,b,c.
184			// Valeria di Felice fits parameter values are:
185			// protons: a,b,c= 2.70, 2.15, 0.21
186			// electrons: a,b,c= 0.0638, 1.248e-16, -38.248
187			void PamVMCPrimaryGenerator::GenSpe_3par(Double_t PEmin, Double_t PEmax, Double_t a, Double_t b, Double_t c)
188			{
189	nikolas	1.1
190	pizzolot	1.6	Bool_t found=0;
191			Double_t funct_min, funct_max;
192			funct_max = function3par(PEmin,a,b,c);
193			funct_min = function3par(PEmax,a,b,c);
194			//
195			Double_t wurfP;
196			Double_t wurfy ;
197			//printf("in genspe3par^^^^%f ^^%f ^^^^^^^^%f ^^^^^%f^^^^^^^\n",PEmin,PEmax,funct_min,funct_max);
198			//printf("in par^^ %f %f %f \n",a,b,c);
199			while( found==0 )
200			{
201			wurfP = frandom->Uniform(PEmin,PEmax);
202			wurfy = frandom->Uniform(funct_min,funct_max);
203			if( wurfy<(function3par(wurfP,a,b,c) ))
204			{
205			// this is ok!
206			fprim.fP0=wurfP;
207			found=1;
208			}
209			}
210			//printf("exit+++++++++++++++++++ %f %f \n",wurfP,fprim.fP0);
211			}
212
213
214
215			// cecilia pizzolotto
216			void PamVMCPrimaryGenerator::GenSpe_Flat(Double_t PEmin, Double_t PEmax, Double_t gamma, Bool_t isEnergy)
217			{
218			// Generates a flat spectrum from PEmin to PElim. Then a power law
219			Double_t PElim = 1.;
220			//Double_t alpha = 1.+gamma; //integral spectral index
221
222			Bool_t okflag=0.;
223			Double_t throw_x =0.;
224			Double_t throw_y =0.;
225
226			while(okflag==0)
227			{
228			throw_x=frandom->Uniform(PEmin,PEmax);
229			// cout<<" x "<<throw_x<<endl;
230			if(throw_x<=PElim)
231			{
232			okflag=1.;
233			}
234			else
235			{
236			throw_y=frandom->Uniform(0.,1.);
237			if( throw_y<(1*pow(throw_x,gamma)))
238			{
239			okflag=1.;
240			}
241			}
242			}
243			fprim.fP0=throw_x;
244			//h->Fill(fprimf.P0);
245			okflag=0.; // reset
246
247	nikolas	1.2	if(isEnergy) fprim.fP0=KinEToMomentum(fprim.fP0);
248	nikolas	1.1
249	nikolas	1.2	}
250	pizzolot	1.6
251			// Spherical distribution -- Test by Cecilia P july 2009 ----
252			// flusso isotropo su 2pi
253			void PamVMCPrimaryGenerator::GenSphericalPhiThe()
254			{
255			// Generate phi theta
256			Double_t theta=0.;
257			Double_t phi=0.;
258
259			Double_t xcos = sqrt( frandom->Uniform(0.,1.) );
260			theta = acos(xcos); //RAD
261
262			phi = frandom->Uniform(0.,2.*Pi());
263
264			SetDirection(theta, phi);
265			return;
266			}
267
268
269
270
271
272			void PamVMCPrimaryGenerator::GenSphPhiThe(Double_t xmin, Double_t xmax, Double_t ymin, Double_t ymax,
273			Double_t zmin, Double_t zmax)
274			{
275			Bool_t trkGood = kFALSE;
276			Double_t theta = 999.;
277			Double_t phi = 0.;
278			Double_t x2,y2,x3,y3;
279			Double_t x0,y0,z0;
280
281			//static const Double_t rad2deg = 57.2958;
282			// S21 and S31 position/size taken as reference (z on top of det)
283			// constraint: must pass throuth these planes
284			static const Double_t s2_xmax=9.05, s2_ymax=7.55, s2_z=73.439; // z on top of det
285			static const Double_t s3_xmax=9.05, s3_ymax=7.55, s3_z=26.093; // z on top of det
286
287			//Double_t thetamax=3.14;
288			//thetamax = atan((xmax+s3_xmax)/(zmax-s3_z));
289			//cout<<" Quanto è il theta max? "<<thetamax<<" in deg "<<thetamax*(90./Pi())<<endl;
290
291			while (trkGood!=kTRUE)
292			{
293			x0= frandom->Uniform(xmin,xmax);
294			y0= frandom->Uniform(ymin,ymax);
295			z0= frandom->Uniform(zmin,zmax);
296
297			// Generate phi theta
298			theta=999.; // init
299			while (theta>=0.65) // take only theta smaller than 37deg=0.65rad
300			{
301			Double_t xcos = sqrt( frandom->Uniform(0.,1.) );
302			theta = acos(xcos); //RAD
303			}
304			phi = frandom->Uniform(0.,2.*Pi());
305
306			// Calculate xy at the constraint
307			Double_t fact2 = (s2_z-z0)/cos(theta);
308			x2 = x0 + fabs(fact2) * sin(theta) * cos(phi);
309			y2 = y0 + fabs(fact2) * sin(theta) * sin(phi);
310			Double_t fact3 = (s3_z-z0)/cos(theta);
311			x3 = x0 + fabs(fact3) * sin(theta) * cos(phi);
312			y3 = y0 + fabs(fact3) * sin(theta) * sin(phi);
313
314			//cout<<" x/y0= "<<x0<<" "<<y0<<" x/y2= "<<fact2sin(theta)cos(phi)<<" "<<x2<<" xy3= "<<
315			// fact3sin(theta)cos(phi)<<" "<<x3<<" phi/the "<<phi(90./Pi())<<" "<<theta(90./Pi())<<endl;
316
317			// Test condition on the direction
318			if ( Abs(x2) <= Abs(s2_xmax) && Abs(y2) <= Abs(s2_ymax) &&
319			Abs(x3) <= Abs(s3_xmax) && Abs(y3) <= Abs(s3_ymax) ) {
320			trkGood = kTRUE;
321			//cout<<" x/y0= "<<x0<<" "<<y0<<" x/y2= "<<fact2sin(theta)cos(phi)<<" "<<x2<<" xy3= "<<
322			// fact3sin(theta)cos(phi)<<" "<<x3<<endl;
323			}
324			}
325
326			// Set direction and position:
327			SetDirection(theta, phi);
328			SetPosition(x0, y0, z0);
329
330			return;
331			}