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cc80f89e | 1 | /************************************************************************** |
2 | * Copyright(c) 1998-1999, ALICE Experiment at CERN, All rights reserved. * | |
3 | * * | |
4 | * Author: The ALICE Off-line Project. * | |
5 | * Contributors are mentioned in the code where appropriate. * | |
6 | * * | |
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 | **************************************************************************/ | |
15 | ||
88cb7938 | 16 | /* $Id$ */ |
cc80f89e | 17 | |
18 | static int PropagateTo(TVector &x, Double_t fX, Double_t xk) { | |
19 | if (TMath::Abs(x(2)*xk - x(3)) >= 0.999) { | |
20 | cerr<<"Propagation failed !\n"; | |
21 | return 0; | |
22 | } | |
23 | ||
24 | Double_t x1=fX, x2=x1+(xk-x1), dx=x2-x1;//, y1=x(0), z1=x(1); | |
25 | Double_t c1=x(2)*x1 - x(3), r1=sqrt(1.- c1*c1); | |
26 | Double_t c2=x(2)*x2 - x(3), r2=sqrt(1.- c2*c2); | |
27 | ||
28 | x(0) += dx*(c1+c2)/(r1+r2); | |
29 | x(1) += dx*(c1+c2)/(c1*r2 + c2*r1)*x(4); | |
30 | ||
31 | return 1; | |
32 | } | |
33 | ||
34 | static int Rotate(TVector &x, Double_t fX, Double_t alpha) { | |
35 | Double_t x1=fX, y1=x(0); | |
36 | Double_t ca=cos(alpha), sa=sin(alpha); | |
37 | Double_t r1=x(2)*fX - x(3); | |
38 | ||
39 | fX = x1*ca + y1*sa; | |
40 | x(0)=-x1*sa + y1*ca; | |
41 | x(3)=x(3)*ca + (x(2)*y1 + sqrt(1.- r1*r1))*sa; | |
42 | ||
43 | Double_t r2=x(2)*fX - x(3); | |
44 | if (TMath::Abs(r2) >= 0.999) { | |
45 | //cerr<<"Rotation failed !\n"; | |
46 | return 0; | |
47 | } | |
48 | ||
49 | Double_t y0=x(0) + sqrt(1.- r2*r2)/x(2); | |
50 | if ((x(0)-y0)*x(2) >= 0.) { | |
51 | //cerr<<"Rotation failed !!!\n"; | |
52 | return 0; | |
53 | } | |
54 | ||
55 | return 1; | |
56 | } | |
57 | ||
58 | //_____________________________________________________________________________ | |
59 | static int templ(TVector par, Double_t x, Double_t dy, Double_t dz, | |
60 | const AliTPCSector *sec, int s, int rf=0) | |
61 | { | |
62 | //----------------------------------------------------------------- | |
63 | // This function tries to find a track prolongation. | |
64 | // | |
65 | // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch | |
66 | //----------------------------------------------------------------- | |
67 | int accepted=0; | |
68 | const int ROWS_TO_SKIP=100; | |
69 | int try_again=ROWS_TO_SKIP; | |
70 | Double_t alpha=sec->GetAlpha(); | |
71 | int ns=int(2*TMath::Pi()/alpha+0.5); | |
72 | ||
73 | Double_t xold=x; | |
74 | for (int nr=sec->GetRowNumber(x)-1; nr>=rf; nr--,xold=x) { | |
75 | //cerr<<nr<<endl; | |
76 | Double_t x=sec->GetX(nr), ymax=sec->GetMaxY(nr); | |
77 | if (!PropagateTo(par,xold,x)) return 0; | |
78 | ||
79 | AliTPCcluster *cl=0; | |
80 | const AliTPCRow& row=sec[s][nr]; | |
81 | Double_t road=dy, y=par(0), z=par(1); | |
82 | ||
83 | if (road>30) { | |
84 | return 0; | |
85 | } | |
86 | ||
87 | if (row) { | |
88 | for (int i=row.Find(y-road); i<row; i++) { | |
89 | AliTPCcluster* c=(AliTPCcluster*)(row[i]); | |
90 | if (c->fY > y+road) break; | |
91 | if (TMath::Abs(c->fZ - z) > dz) continue; | |
92 | cl=c; | |
93 | } | |
94 | } | |
95 | if (cl) { | |
96 | par(0)=cl->fY; par(1)=cl->fZ; | |
97 | //dy=TMath::Sqrt(cl->fSigmaY2); dz=TMath::Sqrt(cl->fSigmaZ2); | |
98 | //cerr<<nr<<' '<<cl->fTracks[0]<<' '<<cl->fTracks[1]<<' '<<cl->fTracks[2]<<endl; | |
99 | accepted++; | |
100 | try_again=ROWS_TO_SKIP; | |
101 | } else { | |
102 | if (try_again==0) break; | |
103 | if (y > ymax) { | |
104 | s = (s+1) % ns; | |
105 | if (!Rotate(par,x,alpha)) return 0; | |
106 | dy*=2; | |
107 | } else if (y <-ymax) { | |
108 | s = (s-1+ns) % ns; | |
109 | if (!Rotate(par,x,-alpha)) return 0; | |
110 | dy*=2; | |
111 | } | |
112 | try_again--; | |
113 | } | |
114 | } | |
115 | ||
116 | //cerr<<endl; | |
117 | return accepted; | |
118 | } | |
119 | ||
120 |