Particles array has one entry more than pythia particle list. Upper bound of

[u/mrichter/AliRoot.git] / STEER / AliLego.cxx

/**************************************************************************
 * 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 1.11  2000/03/22 13:42:26  fca
SetGenerator does not replace an existing generator, ResetGenerator does

Revision 1.10  2000/02/23 16:25:22  fca
AliVMC and AliGeant3 classes introduced
ReadEuclid moved from AliRun to AliModule

Revision 1.9  1999/12/03 10:54:01  fca
Fix lego summary

Revision 1.8  1999/10/01 09:54:33  fca
Correct logics for Lego StepManager

Revision 1.7  1999/09/29 09:24:29  fca
Introduction of the Copyright and cvs Log

*/

//////////////////////////////////////////////////////////////
//////////////////////////////////////////////////////////////
//                            
//  Utility class to evaluate the material budget from
//  a given radius to the surface of an arbitrary cylinder
//  along radial directions from the centre:
// 
//   - radiation length
//   - Interaction length
//   - g/cm2
// 
//  Geantinos are shot in the bins in the fNtheta bins in theta
//  and fNphi bins in phi with specified rectangular limits.
//  The statistics are accumulated per
//    fRadMin < r < fRadMax    and  <0 < z < fZMax
//
//  To activate this option, you can do:
//      Root > gAlice.RunLego();
//  or  Root > .x menu.C  then select menu item "RunLego"
//  Note that when calling gAlice->RunLego, an optional list
//  of arguments may be specified.
//
//Begin_Html
/*
<img src="picts/alilego.gif">
*/
//End_Html
//
//////////////////////////////////////////////////////////////

#include "TMath.h"
#include "AliLego.h"
#include "AliRun.h"
#include "AliConst.h"
#include "AliMC.h"

ClassImp(AliLego)


//___________________________________________
AliLego::AliLego()
{
   fHistRadl = 0;
   fHistAbso = 0;
   fHistGcm2 = 0;
   fHistReta = 0;
}

//___________________________________________
AliLego::AliLego(const char *title, Int_t ntheta, Float_t themin, Float_t themax,
		 Int_t nphi, Float_t phimin, Float_t phimax,
		 Float_t rmin, Float_t rmax, Float_t zmax)
  : TNamed("Lego Generator",title)
{
// specify the angular limits and the size of the rectangular box
   
   fGener = new AliLegoGenerator(ntheta, themin, themax,
		       nphi, phimin, phimax, rmin, rmax, zmax);
   
   gAlice->ResetGenerator(fGener);

   Float_t etamin = -TMath::Log(TMath::Tan(TMath::Min((Double_t)themax*kDegrad/2,TMath::Pi()/2-1.e-10)));
   Float_t etamax = -TMath::Log(TMath::Tan(TMath::Max((Double_t)themin*kDegrad/2,              1.e-10)));

   fHistRadl = new TH2F("hradl","Radiation length map",    
			nphi,phimin,phimax,ntheta,themin,themax);
   fHistAbso = new TH2F("habso","Interaction length map",  
			nphi,phimin,phimax,ntheta,themin,themax);
   fHistGcm2 = new TH2F("hgcm2","g/cm2 length map",        
			nphi,phimin,phimax,ntheta,themin,themax);
   fHistReta = new TH2F("hetar","Radiation length vs. eta",
			nphi,phimin,phimax,ntheta,etamin,etamax);

}

//___________________________________________
AliLego::~AliLego()
{
   delete fHistRadl;
   delete fHistAbso;
   delete fHistGcm2;
   delete fHistReta;
}


//___________________________________________
void AliLego::Run()
{
   // loop on phi,theta bins
   gMC->InitLego();
   Float_t thed, phid, eta;
   for (Int_t i=0; i<=fGener->Nphi()*fGener->Ntheta(); ++i) {
// --- Set to 0 radiation length, absorption length and g/cm2 ---
     fTotRadl = 0;
     fTotAbso = 0;
     fTotGcm2 = 0;
     
     gMC->ProcessEvent();
     
     thed = fGener->CurTheta()*kRaddeg;
     phid = fGener->CurPhi()*kRaddeg;
     eta  = -TMath::Log(TMath::Tan(TMath::Max(
	     TMath::Min((Double_t)(fGener->CurTheta())/2,
			TMath::Pi()/2-1.e-10),1.e-10)));

     fHistRadl->Fill(phid,thed,fTotRadl);
     fHistAbso->Fill(phid,thed,fTotAbso);
     fHistGcm2->Fill(phid,thed,fTotGcm2);
     fHistReta->Fill(phid,eta,fTotRadl);
     gAlice->FinishEvent();
   }
   // store histograms in current Root file
   fHistRadl->Write();
   fHistAbso->Write();
   fHistGcm2->Write();
   fHistReta->Write();
}

//___________________________________________
void AliLego::StepManager()
{
// called from AliRun::Stepmanager from gustep.
// Accumulate the 3 parameters step by step
  
   static Float_t t;
   Float_t a,z,dens,radl,absl;
   Int_t i;
   
   Float_t step  = gMC->TrackStep();
       
   Float_t vect[3], dir[3];
   TLorentzVector pos, mom;

   gMC->TrackPosition(pos);  
   gMC->TrackMomentum(mom);
   gMC->CurrentMaterial(a,z,dens,radl,absl);
   
   if (z < 1) return;
   
// --- See if we have to stop now
   if (TMath::Abs(pos[2]) > fGener->ZMax()  || 
       pos[0]*pos[0] +pos[1]*pos[1] > fGener->RadMax()*fGener->RadMax()) {
     if (gMC->TrackLength()) {
       // Not the first step, add past contribution
       fTotAbso += t/absl;
       fTotRadl += t/radl;
       fTotGcm2 += t*dens;
     }
     gMC->StopTrack();
     return;
   }

// --- See how long we have to go
   for(i=0;i<3;++i) {
     vect[i]=pos[i];
     dir[i]=mom[i];
   }

   t  = fGener->PropagateCylinder(vect,dir,fGener->RadMax(),fGener->ZMax());

   if(step) {
     fTotAbso += step/absl;
     fTotRadl += step/radl;
     fTotGcm2 += step*dens;
   }
}

ClassImp(AliLegoGenerator)

//___________________________________________
AliLegoGenerator::AliLegoGenerator(Int_t ntheta, Float_t themin,
				   Float_t themax, Int_t nphi, 
				   Float_t phimin, Float_t phimax,
				   Float_t rmin, Float_t rmax, Float_t zmax) :
  AliGenerator(0), fRadMin(rmin), fRadMax(rmax), fZMax(zmax), fNtheta(ntheta),
  fNphi(nphi), fThetaBin(ntheta), fPhiBin(-1), fCurTheta(0), fCurPhi(0)
  
{
  SetPhiRange(phimin,phimax);
  SetThetaRange(themin,themax);
  SetName("Lego");
}


//___________________________________________
void AliLegoGenerator::Generate()
{
// Create a geantino with kinematics corresponding to the current
// bins in theta and phi.
   
  //
  // Rootinos are 0
   const Int_t mpart = 0;
   Float_t orig[3], pmom[3];
   Float_t t, cost, sint, cosp, sinp;
   
   // Prepare for next step
   if(fThetaBin>=fNtheta-1)
     if(fPhiBin>=fNphi-1) {
       Warning("Generate","End of Lego Generation");
       return;
     } else { 
       fPhiBin++;
       printf("Generating rays in phi bin:%d\n",fPhiBin);
       fThetaBin=0;
     } else fThetaBin++;

   fCurTheta = (fThetaMin+(fThetaBin+0.5)*(fThetaMax-fThetaMin)/fNtheta);
   fCurPhi   = (fPhiMin+(fPhiBin+0.5)*(fPhiMax-fPhiMin)/fNphi);
   cost      = TMath::Cos(fCurTheta);
   sint      = TMath::Sin(fCurTheta);
   cosp      = TMath::Cos(fCurPhi);
   sinp      = TMath::Sin(fCurPhi);
   
   pmom[0] = cosp*sint;
   pmom[1] = sinp*sint;
   pmom[2] = cost;
   
   // --- Where to start
   orig[0] = orig[1] = orig[2] = 0;
   Float_t dalicz = 3000;
   if (fRadMin > 0) {
     t = PropagateCylinder(orig,pmom,fRadMin,dalicz);
     orig[0] = pmom[0]*t;
     orig[1] = pmom[1]*t;
     orig[2] = pmom[2]*t;
     if (TMath::Abs(orig[2]) > fZMax) return;
   }
   
   Float_t polar[3]={0.,0.,0.};
   Int_t ntr;
   gAlice->SetTrack(1, 0, mpart, pmom, orig, polar, 0, "LEGO ray", ntr);

}

//___________________________________________
Float_t AliLegoGenerator::PropagateCylinder(Float_t *x, Float_t *v, Float_t r, Float_t z)
{
// Propagate to cylinder from inside

   Double_t hnorm, sz, t, t1, t2, t3, sr;
   Double_t d[3];
   const Float_t kSmall  = 1e-8;
   const Float_t kSmall2 = kSmall*kSmall;

// ---> Find intesection with Z planes
   d[0]  = v[0];
   d[1]  = v[1];
   d[2]  = v[2];
   hnorm = TMath::Sqrt(1/(d[0]*d[0]+d[1]*d[1]+d[2]*d[2]));
   d[0] *= hnorm;
   d[1] *= hnorm;
   d[2] *= hnorm;
   if (d[2] > kSmall)       sz = (z-x[2])/d[2];
   else if (d[2] < -kSmall) sz = -(z+x[2])/d[2];
   else                     sz = 1.e10;  // ---> Direction parallel to X-Y, no intersection

// ---> Intersection with cylinders
//      Intersection point (x,y,z)
//      (x,y,z) is on track :    x=X(1)+t*D(1)
//                               y=X(2)+t*D(2)
//                               z=X(3)+t*D(3)
//      (x,y,z) is on cylinder : x**2 + y**2 = R**2
//
//      (D(1)**2+D(2)**2)*t**2
//      +2.*(X(1)*D(1)+X(2)*D(2))*t
//      +X(1)**2+X(2)**2-R**2=0
// ---> Solve second degree equation
   t1 = d[0]*d[0] + d[1]*d[1];
   if (t1 <= kSmall2) {
      t = sz;  // ---> Track parallel to the z-axis, take distance to planes
   } else {
      t2 = x[0]*d[0] + x[1]*d[1];
      t3 = x[0]*x[0] + x[1]*x[1];
      // ---> It should be positive, but there may be numerical problems
      sr = (t2 +TMath::Sqrt(TMath::Max(t2*t2-(t3-r*r)*t1,0.)))/t1;
      // ---> Find minimum distance between planes and cylinder
      t  = TMath::Min(sz,sr);
   }
   return t;
}