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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/* $Id$ */
17
18//------------------------------------------------------------------------
19// Generic Lego generator code
20// Uses geantino rays to check the material distributions and detector's
21// geometry
22// Author: A.Morsch
23//------------------------------------------------------------------------
24
25#include "AliLegoGenerator.h"
26#include "AliRun.h"
27#include "AliMC.h"
28#include "AliLog.h"
29
30ClassImp(AliLegoGenerator)
31
32//_______________________________________________________________________
33AliLegoGenerator::AliLegoGenerator():
34 fRadMin(0),
35 fRadMax(0),
36 fZMax(0),
37 fNCoor1(0),
38 fNCoor2(0),
39 fCoor1Min(0),
40 fCoor1Max(0),
41 fCoor2Min(0),
42 fCoor2Max(0),
43 fCoor1Bin(-1),
44 fCoor2Bin(-1),
45 fCurCoor1(0),
46 fCurCoor2(0)
47{
48 //
49 // Default Constructor
50 //
51 SetName("Lego");
52}
53
54//_______________________________________________________________________
55AliLegoGenerator::AliLegoGenerator(Int_t nc1, Float_t c1min,
56 Float_t c1max, Int_t nc2,
57 Float_t c2min, Float_t c2max,
58 Float_t rmin, Float_t rmax, Float_t zmax):
59 AliGenerator(0),
60 fRadMin(rmin),
61 fRadMax(rmax),
62 fZMax(zmax),
63 fNCoor1(nc1),
64 fNCoor2(nc2),
65 fCoor1Min(0),
66 fCoor1Max(0),
67 fCoor2Min(0),
68 fCoor2Max(0),
69 fCoor1Bin(nc1),
70 fCoor2Bin(-1),
71 fCurCoor1(0),
72 fCurCoor2(0)
73{
74 //
75 // Standard generator for Lego rays
76 //
77 SetName("Lego");
78 SetCoor1Range(nc1, c1min, c1max);
79 SetCoor2Range(nc2, c2min, c2max);
80}
81
82//_______________________________________________________________________
83void AliLegoGenerator::Generate()
84{
85 // Create a geantino with kinematics corresponding to the current bins
86 // Here: Coor1 = theta
87 // Coor2 = phi.
88
89 //
90 // Rootinos are 0
91 const Int_t kMpart = 0;
92 Float_t orig[3], pmom[3];
93 Float_t t, cost, sint, cosp, sinp;
94 if (fCoor1Bin==-1) fCoor1Bin=fNCoor1;
95 // Prepare for next step
96 if(fCoor1Bin>=fNCoor1-1)
97 if(fCoor2Bin>=fNCoor2-1) {
98 AliWarning("End of Lego Generation");
99 return;
100 } else {
101 fCoor2Bin++;
102 AliDebug(1, Form("Generating rays in phi bin:%d",fCoor2Bin));
103 fCoor1Bin=0;
104 } else fCoor1Bin++;
105
106 fCurCoor1 = (fCoor1Min+(fCoor1Bin+0.5)*(fCoor1Max-fCoor1Min)/fNCoor1);
107 fCurCoor2 = (fCoor2Min+(fCoor2Bin+0.5)*(fCoor2Max-fCoor2Min)/fNCoor2);
108 cost = TMath::Cos(fCurCoor1 * TMath::Pi()/180.);
109 sint = TMath::Sin(fCurCoor1 * TMath::Pi()/180.);
110 cosp = TMath::Cos(fCurCoor2 * TMath::Pi()/180.);
111 sinp = TMath::Sin(fCurCoor2 * TMath::Pi()/180.);
112
113 pmom[0] = cosp*sint;
114 pmom[1] = sinp*sint;
115 pmom[2] = cost;
116
117 // --- Where to start
118 orig[0] = orig[1] = orig[2] = 0;
119 Float_t dalicz = 3000;
120 if (fRadMin > 0) {
121 t = PropagateCylinder(orig,pmom,fRadMin,dalicz);
122 orig[0] = pmom[0]*t;
123 orig[1] = pmom[1]*t;
124 orig[2] = pmom[2]*t;
125 if (TMath::Abs(orig[2]) > fZMax) return;
126 }
127
128 Float_t polar[3]={0.,0.,0.};
129 Int_t ntr;
130 gAlice->GetMCApp()->PushTrack(1, -1, kMpart, pmom, orig, polar, 0, kPPrimary, ntr);
131
132}
133
134//_______________________________________________________________________
135Float_t AliLegoGenerator::PropagateCylinder(Float_t *x, Float_t *v, Float_t r,
136 Float_t z)
137{
138 //
139 // Propagate to cylinder from inside
140 //
141 Double_t hnorm, sz, t, t1, t2, t3, sr;
142 Double_t d[3];
143 const Float_t kSmall = 1e-8;
144 const Float_t kSmall2 = kSmall*kSmall;
145
146// ---> Find intesection with Z planes
147 d[0] = v[0];
148 d[1] = v[1];
149 d[2] = v[2];
150 hnorm = TMath::Sqrt(1/(d[0]*d[0]+d[1]*d[1]+d[2]*d[2]));
151 d[0] *= hnorm;
152 d[1] *= hnorm;
153 d[2] *= hnorm;
154 if (d[2] > kSmall) sz = (z-x[2])/d[2];
155 else if (d[2] < -kSmall) sz = -(z+x[2])/d[2];
156 else sz = 1.e10; // ---> Direction parallel to X-Y, no intersection
157
158// ---> Intersection with cylinders
159// Intersection point (x,y,z)
160// (x,y,z) is on track : x=X(1)+t*D(1)
161// y=X(2)+t*D(2)
162// z=X(3)+t*D(3)
163// (x,y,z) is on cylinder : x**2 + y**2 = R**2
164//
165// (D(1)**2+D(2)**2)*t**2
166// +2.*(X(1)*D(1)+X(2)*D(2))*t
167// +X(1)**2+X(2)**2-R**2=0
168// ---> Solve second degree equation
169 t1 = d[0]*d[0] + d[1]*d[1];
170 if (t1 <= kSmall2) {
171 t = sz; // ---> Track parallel to the z-axis, take distance to planes
172 } else {
173 t2 = x[0]*d[0] + x[1]*d[1];
174 t3 = x[0]*x[0] + x[1]*x[1];
175 // ---> It should be positive, but there may be numerical problems
176 sr = (-t2 +TMath::Sqrt(TMath::Max(t2*t2-(t3-r*r)*t1,0.)))/t1;
177 // ---> Find minimum distance between planes and cylinder
178 t = TMath::Min(sz,sr);
179 }
180 return t;
181}
182
183