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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 | ||
16 | /* | |
17 | $Log$ | |
18 | Revision 1.1.2.2 2000/04/10 11:40:46 kowal2 | |
19 | ||
20 | Needed for tracking | |
21 | ||
22 | */ | |
23 | ||
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"; | |
27 | return 0; | |
28 | } | |
29 | ||
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); | |
33 | ||
34 | x(0) += dx*(c1+c2)/(r1+r2); | |
35 | x(1) += dx*(c1+c2)/(c1*r2 + c2*r1)*x(4); | |
36 | ||
37 | return 1; | |
38 | } | |
39 | ||
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); | |
44 | ||
45 | fX = x1*ca + y1*sa; | |
46 | x(0)=-x1*sa + y1*ca; | |
47 | x(3)=x(3)*ca + (x(2)*y1 + sqrt(1.- r1*r1))*sa; | |
48 | ||
49 | Double_t r2=x(2)*fX - x(3); | |
50 | if (TMath::Abs(r2) >= 0.999) { | |
51 | //cerr<<"Rotation failed !\n"; | |
52 | return 0; | |
53 | } | |
54 | ||
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"; | |
58 | return 0; | |
59 | } | |
60 | ||
61 | return 1; | |
62 | } | |
63 | ||
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) | |
67 | { | |
68 | //----------------------------------------------------------------- | |
69 | // This function tries to find a track prolongation. | |
70 | // | |
71 | // Origin: Iouri Belikov, CERN, Jouri.Belikov@cern.ch | |
72 | //----------------------------------------------------------------- | |
73 | int accepted=0; | |
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); | |
78 | ||
79 | Double_t xold=x; | |
80 | for (int nr=sec->GetRowNumber(x)-1; nr>=rf; nr--,xold=x) { | |
81 | //cerr<<nr<<endl; | |
82 | Double_t x=sec->GetX(nr), ymax=sec->GetMaxY(nr); | |
83 | if (!PropagateTo(par,xold,x)) return 0; | |
84 | ||
85 | AliTPCcluster *cl=0; | |
86 | const AliTPCRow& row=sec[s][nr]; | |
87 | Double_t road=dy, y=par(0), z=par(1); | |
88 | ||
89 | if (road>30) { | |
90 | return 0; | |
91 | } | |
92 | ||
93 | if (row) { | |
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; | |
98 | cl=c; | |
99 | } | |
100 | } | |
101 | if (cl) { | |
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; | |
105 | accepted++; | |
106 | try_again=ROWS_TO_SKIP; | |
107 | } else { | |
108 | if (try_again==0) break; | |
109 | if (y > ymax) { | |
110 | s = (s+1) % ns; | |
111 | if (!Rotate(par,x,alpha)) return 0; | |
112 | dy*=2; | |
113 | } else if (y <-ymax) { | |
114 | s = (s-1+ns) % ns; | |
115 | if (!Rotate(par,x,-alpha)) return 0; | |
116 | dy*=2; | |
117 | } | |
118 | try_again--; | |
119 | } | |
120 | } | |
121 | ||
122 | //cerr<<endl; | |
123 | return accepted; | |
124 | } | |
125 | ||
126 |