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. *
7 * Permission to use, copy, modify and distribute this software and its *
8 * documentation strictly for non-commercial purposes is hereby granted *
9 * without fee, provided that the above copyright notice appears in all *
10 * copies and that both the copyright notice and this permission notice *
11 * appear in the supporting documentation. The authors make no claims *
12 * about the suitability of this software for any purpose. It is *
13 * provided "as is" without express or implied warranty. *
14 **************************************************************************/
18 Revision 1.1.2.2 2000/04/10 11:40:46 kowal2
24 static int PropagateTo(TVector &x, Double_t fX, Double_t xk) {
25 if (TMath::Abs(x(2)*xk - x(3)) >= 0.999) {
26 cerr<<"Propagation failed !\n";
30 Double_t x1=fX, x2=x1+(xk-x1), dx=x2-x1;//, y1=x(0), z1=x(1);
31 Double_t c1=x(2)*x1 - x(3), r1=sqrt(1.- c1*c1);
32 Double_t c2=x(2)*x2 - x(3), r2=sqrt(1.- c2*c2);
34 x(0) += dx*(c1+c2)/(r1+r2);
35 x(1) += dx*(c1+c2)/(c1*r2 + c2*r1)*x(4);
40 static int Rotate(TVector &x, Double_t fX, Double_t alpha) {
41 Double_t x1=fX, y1=x(0);
42 Double_t ca=cos(alpha), sa=sin(alpha);
43 Double_t r1=x(2)*fX - x(3);
47 x(3)=x(3)*ca + (x(2)*y1 + sqrt(1.- r1*r1))*sa;
49 Double_t r2=x(2)*fX - x(3);
50 if (TMath::Abs(r2) >= 0.999) {
51 //cerr<<"Rotation failed !\n";
55 Double_t y0=x(0) + sqrt(1.- r2*r2)/x(2);
56 if ((x(0)-y0)*x(2) >= 0.) {
57 //cerr<<"Rotation failed !!!\n";
64 //_____________________________________________________________________________
65 static int templ(TVector par, Double_t x, Double_t dy, Double_t dz,
66 const AliTPCSector *sec, int s, int rf=0)
68 //-----------------------------------------------------------------
69 // This function tries to find a track prolongation.
71 // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch
72 //-----------------------------------------------------------------
74 const int ROWS_TO_SKIP=100;
75 int try_again=ROWS_TO_SKIP;
76 Double_t alpha=sec->GetAlpha();
77 int ns=int(2*TMath::Pi()/alpha+0.5);
80 for (int nr=sec->GetRowNumber(x)-1; nr>=rf; nr--,xold=x) {
82 Double_t x=sec->GetX(nr), ymax=sec->GetMaxY(nr);
83 if (!PropagateTo(par,xold,x)) return 0;
86 const AliTPCRow& row=sec[s][nr];
87 Double_t road=dy, y=par(0), z=par(1);
94 for (int i=row.Find(y-road); i<row; i++) {
95 AliTPCcluster* c=(AliTPCcluster*)(row[i]);
96 if (c->fY > y+road) break;
97 if (TMath::Abs(c->fZ - z) > dz) continue;
102 par(0)=cl->fY; par(1)=cl->fZ;
103 //dy=TMath::Sqrt(cl->fSigmaY2); dz=TMath::Sqrt(cl->fSigmaZ2);
104 //cerr<<nr<<' '<<cl->fTracks[0]<<' '<<cl->fTracks[1]<<' '<<cl->fTracks[2]<<endl;
106 try_again=ROWS_TO_SKIP;
108 if (try_again==0) break;
111 if (!Rotate(par,x,alpha)) return 0;
113 } else if (y <-ymax) {
115 if (!Rotate(par,x,-alpha)) return 0;