Use gMC and not pMC everywhere
[u/mrichter/AliRoot.git] / STEER / AliLego.cxx
CommitLineData
fe4da5cc 1//////////////////////////////////////////////////////////////
2//////////////////////////////////////////////////////////////
3//
4// Utility class to evaluate the material budget from
5// a given radius to the surface of an arbitrary cylinder
6// along radial directions from the centre:
7//
8// - radiation length
9// - Interaction length
10// - g/cm2
11//
12// Geantinos are shot in the bins in the fNtheta bins in theta
13// and fNphi bins in phi with specified rectangular limits.
14// The statistics are accumulated per
15// fRadMin < r < fRadMax and <0 < z < fZMax
16//
17// To activate this option, you can do:
18// Root > gAlice.RunLego();
19// or Root > .x menu.C then select menu item "RunLego"
20// Note that when calling gAlice->RunLego, an optional list
21// of arguments may be specified.
22//
23//Begin_Html
24/*
1439f98e 25<img src="picts/alilego.gif">
fe4da5cc 26*/
27//End_Html
28//
29//////////////////////////////////////////////////////////////
30
31#include "TMath.h"
1578254f 32#include "AliLego.h"
fe4da5cc 33#include "AliRun.h"
34#include "AliConst.h"
35
36ClassImp(AliLego)
37
38
39//___________________________________________
40AliLego::AliLego()
41{
42 fHistRadl = 0;
43 fHistAbso = 0;
44 fHistGcm2 = 0;
45 fHistReta = 0;
46}
47
48//___________________________________________
49AliLego::AliLego(const char *name, const char *title)
50 : TNamed(name,title)
51{
52 fHistRadl = 0;
53 fHistAbso = 0;
54 fHistGcm2 = 0;
55 fHistReta = 0;
56}
57
58//___________________________________________
59AliLego::~AliLego()
60{
61 delete fHistRadl;
62 delete fHistAbso;
63 delete fHistGcm2;
64 delete fHistReta;
65}
66
67//___________________________________________
68void AliLego::GenerateKinematics()
69{
70// Create a geantino with kinematics corresponding to the current
71// bins in theta and phi.
72
1578254f 73 //
74 // Rootinos are 0
75 const Int_t mpart = 0;
fe4da5cc 76 Float_t orig[3], pmom[3];
77 Float_t t, cost, sint, cosp, sinp;
78
79// --- Set to 0 radiation length, absorption length and g/cm2 ---
80 fTotRadl = 0;
81 fTotAbso = 0;
82 fTotGcm2 = 0;
83
84 fCurTheta = (fThetaMin+(fThetaBin-0.5)*(fThetaMax-fThetaMin)/fNtheta)*kDegrad;
85 fCurPhi = (fPhiMin+(fPhiBin-0.5)*(fPhiMax-fPhiMin)/fNphi)*kDegrad;
86 cost = TMath::Cos(fCurTheta);
87 sint = TMath::Sin(fCurTheta);
88 cosp = TMath::Cos(fCurPhi);
89 sinp = TMath::Sin(fCurPhi);
90
91 pmom[0] = cosp*sint;
92 pmom[1] = sinp*sint;
93 pmom[2] = cost;
94
95// --- Where to start
96 orig[0] = orig[1] = orig[2] = 0;
97 Float_t dalicz = 3000;
98 if (fRadMin > 0) {
99 t = PropagateCylinder(orig,pmom,fRadMin,dalicz);
100 orig[0] = pmom[0]*t;
101 orig[1] = pmom[1]*t;
102 orig[2] = pmom[2]*t;
103 if (TMath::Abs(orig[2]) > fZMax) return;
104 }
105
106// --- We do start here
107 Float_t polar[3]={0.,0.,0.};
108 Int_t ntr;
109 gAlice->SetTrack(1, 0, mpart, pmom, orig, polar, 0, "LEGO ray", ntr);
110}
111
112//___________________________________________
113void AliLego::Init(Int_t ntheta,Float_t themin,Float_t themax,
114 Int_t nphi,Float_t phimin,Float_t phimax,Float_t rmin,Float_t rmax,
115 Float_t zmax)
116{
117// specify the angular limits and the size of the rectangular box
118 fNtheta = ntheta;
119 fThetaMin = themin;
120 fThetaMax = themax;
121 fNphi = nphi;
122 fPhiMin = phimin;
123 fPhiMax = phimax;
124 fRadMin = rmin;
125 fRadMax = rmax;
126 fZMax = zmax;
127 Float_t etamin = -TMath::Log(TMath::Tan(TMath::Min((Double_t)fThetaMax*kDegrad/2,TMath::Pi()/2-1.e-10)));
128 Float_t etamax = -TMath::Log(TMath::Tan(TMath::Max((Double_t)fThetaMin*kDegrad/2, 1.e-10)));
129
130 fHistRadl = new TH2F("hradl","Radiation length map", nphi,phimin,phimax,ntheta,themin,themax);
131 fHistAbso = new TH2F("habso","Interaction length map", nphi,phimin,phimax,ntheta,themin,themax);
132 fHistGcm2 = new TH2F("hgcm2","g/cm2 length map", nphi,phimin,phimax,ntheta,themin,themax);
133 fHistReta = new TH2F("hetar","Radiation length vs. eta",nphi,phimin,phimax,ntheta,etamin,etamax);
134
135}
136
137//___________________________________________
138Float_t AliLego::PropagateCylinder(Float_t *x, Float_t *v, Float_t r, Float_t z)
139{
140// Propagate to cylinder from inside
141
142 Double_t hnorm, sz, t, t1, t2, t3, sr;
143 Double_t d[3];
144 const Float_t kSmall = 1e-8;
145 const Float_t kSmall2 = kSmall*kSmall;
146
147// ---> Find intesection with Z planes
148 d[0] = v[0];
149 d[1] = v[1];
150 d[2] = v[2];
151 hnorm = TMath::Sqrt(1/(d[0]*d[0]+d[1]*d[1]+d[2]*d[2]));
152 d[0] *= hnorm;
153 d[1] *= hnorm;
154 d[2] *= hnorm;
155 if (d[2] > kSmall) sz = (z-x[2])/d[2];
156 else if (d[2] < -kSmall) sz = -(z+x[2])/d[2];
157 else sz = 1.e10; // ---> Direction parallel to X-Y, no intersection
158
159// ---> Intersection with cylinders
160// Intersection point (x,y,z)
161// (x,y,z) is on track : x=X(1)+t*D(1)
162// y=X(2)+t*D(2)
163// z=X(3)+t*D(3)
164// (x,y,z) is on cylinder : x**2 + y**2 = R**2
165//
166// (D(1)**2+D(2)**2)*t**2
167// +2.*(X(1)*D(1)+X(2)*D(2))*t
168// +X(1)**2+X(2)**2-R**2=0
169// ---> Solve second degree equation
170 t1 = d[0]*d[0] + d[1]*d[1];
171 if (t1 <= kSmall2) {
172 t = sz; // ---> Track parallel to the z-axis, take distance to planes
173 } else {
174 t2 = x[0]*d[0] + x[1]*d[1];
175 t3 = x[0]*x[0] + x[1]*x[1];
176 // ---> It should be positive, but there may be numerical problems
177 sr = (t2 +TMath::Sqrt(TMath::Max(t2*t2-(t3-r*r)*t1,0.)))/t1;
178 // ---> Find minimum distance between planes and cylinder
179 t = TMath::Min(sz,sr);
180 }
181 return t;
182}
183
184//___________________________________________
185void AliLego::Run()
186{
187 // loop on phi,theta bins
cfce8870 188 gMC->InitLego();
fe4da5cc 189 Float_t thed, phid, eta;
190 for (fPhiBin=1; fPhiBin<=fNphi; fPhiBin++) {
191 printf("AliLego Generating rays in phi bin:%d\n",fPhiBin);
192 for (fThetaBin=1; fThetaBin<=fNtheta; fThetaBin++) {
cfce8870 193 gMC->Gtrigi();
194 gMC->Gtrigc();
fe4da5cc 195 GenerateKinematics();
cfce8870 196 gMC->Gtreve_root();
fe4da5cc 197
198 thed = fCurTheta*kRaddeg;
199 phid = fCurPhi*kRaddeg;
200 eta = -TMath::Log(TMath::Tan(TMath::Max(
201 TMath::Min((Double_t)fCurTheta/2,TMath::Pi()/2-1.e-10),1.e-10)));
202 fHistRadl->Fill(phid,thed,fTotRadl);
203 fHistAbso->Fill(phid,thed,fTotAbso);
204 fHistGcm2->Fill(phid,thed,fTotGcm2);
205 fHistReta->Fill(phid,eta,fTotRadl);
206 gAlice->FinishEvent();
207 }
208 }
209 // store histograms in current Root file
210 fHistRadl->Write();
211 fHistAbso->Write();
212 fHistGcm2->Write();
213 fHistReta->Write();
214}
215
216//___________________________________________
217void AliLego::StepManager()
218{
219// called from AliRun::Stepmanager from gustep.
220// Accumulate the 3 parameters step by step
fe4da5cc 221
222 Float_t t, tt;
223 Float_t a,z,dens,radl,absl;
224
cfce8870 225 Float_t step = gMC->TrackStep();
fe4da5cc 226
227 Float_t vect[3], pmom[4];
cfce8870 228 gMC->TrackPosition(vect);
229 gMC->TrackMomentum(pmom);
230 gMC->CurrentMaterial(a,z,dens,radl,absl);
fe4da5cc 231
232 if (z < 1) return;
233
234// --- See if we have to stop now
235 if (TMath::Abs(vect[2]) > fZMax ||
236 vect[0]*vect[0] +vect[1]*vect[1] > fRadMax*fRadMax) {
cfce8870 237 gMC->StopEvent();
fe4da5cc 238 } else {
239
240// --- See how long we have to go
241 t = PropagateCylinder(vect,pmom,fRadMax,fZMax);
242 tt = TMath::Min(step,t);
243
244 fTotAbso += tt/absl;
245 fTotRadl += tt/radl;
246 fTotGcm2 += tt*dens;
247 }
248}
249