]>
Commit | Line | Data |
---|---|---|
a9e2aefa | 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 | $Log$ | |
b45fd22b | 18 | Revision 1.11 2002/03/08 17:25:36 cussonno |
19 | Update absorber energy loss and Branson corrections : simplified functions | |
20 | BransonCorrection and TotalMomentumEnergyLoss. | |
21 | ||
43af2cb6 | 22 | Revision 1.10 2001/04/25 14:50:42 gosset |
23 | Corrections to violations of coding conventions | |
24 | ||
3831f268 | 25 | Revision 1.9 2000/10/16 15:30:40 gosset |
26 | TotalMomentumEnergyLoss: | |
27 | correction for change in the absorber composition (JP Cussonneau) | |
28 | ||
6372a28d | 29 | Revision 1.8 2000/10/02 21:28:09 fca |
30 | Removal of useless dependecies via forward declarations | |
31 | ||
94de3818 | 32 | Revision 1.7 2000/10/02 16:58:29 egangler |
33 | Cleaning of the code : | |
34 | -> coding conventions | |
35 | -> void Streamers | |
36 | -> some useless includes removed or replaced by "class" statement | |
37 | ||
ecfa008b | 38 | Revision 1.6 2000/09/19 09:49:50 gosset |
39 | AliMUONEventReconstructor package | |
40 | * track extrapolation independent from reco_muon.F, use of AliMagF... | |
41 | * possibility to use new magnetic field (automatic from generated root file) | |
42 | ||
a6f03ddb | 43 | Revision 1.5 2000/07/18 16:04:06 gosset |
44 | AliMUONEventReconstructor package: | |
45 | * a few minor modifications and more comments | |
46 | * a few corrections | |
47 | * right sign for Z of raw clusters | |
48 | * right loop over chambers inside station | |
49 | * symmetrized covariance matrix for measurements (TrackChi2MCS) | |
50 | * right sign of charge in extrapolation (ExtrapToZ) | |
51 | * right zEndAbsorber for Branson correction below 3 degrees | |
52 | * use of TVirtualFitter instead of TMinuit for AliMUONTrack::Fit | |
53 | * no parameter for AliMUONTrack::Fit() but more fit parameters in Track object | |
54 | ||
956019b6 | 55 | Revision 1.4 2000/07/03 07:53:31 morsch |
56 | Double declaration problem on HP solved. | |
57 | ||
88962f0c | 58 | Revision 1.3 2000/06/30 10:15:48 gosset |
59 | Changes to EventReconstructor...: | |
60 | precision fit with multiple Coulomb scattering; | |
61 | extrapolation to vertex with Branson correction in absorber (JPC) | |
62 | ||
04b5ea16 | 63 | Revision 1.2 2000/06/15 07:58:49 morsch |
64 | Code from MUON-dev joined | |
65 | ||
a9e2aefa | 66 | Revision 1.1.2.3 2000/06/09 21:03:09 morsch |
67 | Make includes consistent with new file structure. | |
68 | ||
69 | Revision 1.1.2.2 2000/06/09 12:58:05 gosset | |
70 | Removed comment beginnings in Log sections of .cxx files | |
71 | Suppressed most violations of coding rules | |
72 | ||
73 | Revision 1.1.2.1 2000/06/07 14:44:53 gosset | |
74 | Addition of files for track reconstruction in C++ | |
75 | */ | |
76 | ||
3831f268 | 77 | /////////////////////////////////////////////////// |
78 | // | |
79 | // Track parameters | |
80 | // in | |
81 | // ALICE | |
82 | // dimuon | |
83 | // spectrometer | |
a9e2aefa | 84 | // |
3831f268 | 85 | /////////////////////////////////////////////////// |
a9e2aefa | 86 | |
87 | #include <iostream.h> | |
88 | ||
89 | #include "AliCallf77.h" | |
3831f268 | 90 | #include "AliMUON.h" |
a9e2aefa | 91 | #include "AliMUONTrackParam.h" |
3831f268 | 92 | #include "AliMUONChamber.h" |
a9e2aefa | 93 | #include "AliRun.h" |
94de3818 | 94 | #include "AliMagF.h" |
a9e2aefa | 95 | |
96 | ClassImp(AliMUONTrackParam) // Class implementation in ROOT context | |
97 | ||
a6f03ddb | 98 | // A few calls in Fortran or from Fortran (extrap.F). |
99 | // Needed, instead of calls to Geant subroutines, | |
100 | // because double precision is necessary for track fit converging with Minuit. | |
101 | // The "extrap" functions should be translated into C++ ???? | |
a9e2aefa | 102 | #ifndef WIN32 |
a6f03ddb | 103 | # define extrap_onestep_helix extrap_onestep_helix_ |
104 | # define extrap_onestep_helix3 extrap_onestep_helix3_ | |
105 | # define extrap_onestep_rungekutta extrap_onestep_rungekutta_ | |
106 | # define gufld_double gufld_double_ | |
a9e2aefa | 107 | #else |
a6f03ddb | 108 | # define extrap_onestep_helix EXTRAP_ONESTEP_HELIX |
109 | # define extrap_onestep_helix3 EXTRAP_ONESTEP_HELIX3 | |
110 | # define extrap_onestep_rungekutta EXTRAP_ONESTEP_RUNGEKUTTA | |
111 | # define gufld_double GUFLD_DOUBLE | |
a9e2aefa | 112 | #endif |
113 | ||
a6f03ddb | 114 | extern "C" { |
115 | void type_of_call extrap_onestep_helix | |
116 | (Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New); | |
117 | ||
118 | void type_of_call extrap_onestep_helix3 | |
119 | (Double_t &Field, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New); | |
120 | ||
121 | void type_of_call extrap_onestep_rungekutta | |
122 | (Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New); | |
123 | ||
124 | void type_of_call gufld_double(Double_t *Position, Double_t *Field) { | |
125 | // interface to "gAlice->Field()->Field" for arguments in double precision | |
126 | Float_t x[3], b[3]; | |
127 | x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2]; | |
128 | gAlice->Field()->Field(x, b); | |
129 | Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2]; | |
130 | } | |
a9e2aefa | 131 | } |
132 | ||
a9e2aefa | 133 | //__________________________________________________________________________ |
134 | void AliMUONTrackParam::ExtrapToZ(Double_t Z) | |
135 | { | |
136 | // Track parameter extrapolation to the plane at "Z". | |
137 | // On return, the track parameters resulting from the extrapolation | |
138 | // replace the current track parameters. | |
a9e2aefa | 139 | if (this->fZ == Z) return; // nothing to be done if same Z |
140 | Double_t forwardBackward; // +1 if forward, -1 if backward | |
141 | if (Z > this->fZ) forwardBackward = 1.0; | |
142 | else forwardBackward = -1.0; | |
a6f03ddb | 143 | Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ???? |
a9e2aefa | 144 | Int_t iGeant3, stepNumber; |
145 | Int_t maxStepNumber = 5000; // in parameter ???? | |
146 | // For safety: return kTRUE or kFALSE ???? | |
a6f03ddb | 147 | // Parameter vector for calling EXTRAP_ONESTEP |
a9e2aefa | 148 | SetGeant3Parameters(vGeant3, forwardBackward); |
956019b6 | 149 | // sign of charge (sign of fInverseBendingMomentum if forward motion) |
a6f03ddb | 150 | // must be changed if backward extrapolation |
956019b6 | 151 | Double_t chargeExtrap = forwardBackward * |
152 | TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum); | |
a9e2aefa | 153 | Double_t stepLength = 6.0; // in parameter ???? |
154 | // Extrapolation loop | |
155 | stepNumber = 0; | |
156 | while (((forwardBackward * (vGeant3[2] - Z)) <= 0.0) && | |
157 | (stepNumber < maxStepNumber)) { | |
158 | stepNumber++; | |
a6f03ddb | 159 | // Option for switching between helix and Runge-Kutta ???? |
160 | // extrap_onestep_rungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New); | |
161 | extrap_onestep_helix(chargeExtrap, stepLength, vGeant3, vGeant3New); | |
a9e2aefa | 162 | if ((forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z |
163 | // better use TArray ???? | |
164 | for (iGeant3 = 0; iGeant3 < 7; iGeant3++) | |
165 | {vGeant3[iGeant3] = vGeant3New[iGeant3];} | |
166 | } | |
167 | // check maxStepNumber ???? | |
a9e2aefa | 168 | // Interpolation back to exact Z (2nd order) |
169 | // should be in function ???? using TArray ???? | |
170 | Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2 | |
171 | Double_t dZ1i = Z - vGeant3[2]; // 1-i | |
172 | Double_t dZi2 = vGeant3New[2] - Z; // i->2 | |
173 | Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12; | |
174 | Double_t xSecond = | |
175 | ((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12; | |
176 | Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12; | |
177 | Double_t ySecond = | |
178 | ((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12; | |
179 | vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X | |
180 | vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y | |
181 | vGeant3[2] = Z; // Z | |
182 | Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i); | |
183 | Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i); | |
956019b6 | 184 | // (PX, PY, PZ)/PTOT assuming forward motion |
a9e2aefa | 185 | vGeant3[5] = |
186 | 1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT | |
187 | vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT | |
188 | vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT | |
956019b6 | 189 | // Track parameters from Geant3 parameters, |
190 | // with charge back for forward motion | |
191 | GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward); | |
a9e2aefa | 192 | } |
193 | ||
194 | //__________________________________________________________________________ | |
195 | void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward) | |
196 | { | |
197 | // Set vector of Geant3 parameters pointed to by "VGeant3" | |
198 | // from track parameters in current AliMUONTrackParam. | |
199 | // Since AliMUONTrackParam is only geometry, one uses "ForwardBackward" | |
200 | // to know whether the particle is going forward (+1) or backward (-1). | |
201 | VGeant3[0] = this->fNonBendingCoor; // X | |
202 | VGeant3[1] = this->fBendingCoor; // Y | |
203 | VGeant3[2] = this->fZ; // Z | |
204 | Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum); | |
205 | Double_t pZ = | |
206 | pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope); | |
207 | VGeant3[6] = | |
208 | TMath::Sqrt(pYZ * pYZ + | |
209 | pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT | |
210 | VGeant3[5] = ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT | |
211 | VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT | |
212 | VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT | |
213 | } | |
214 | ||
215 | //__________________________________________________________________________ | |
216 | void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge) | |
217 | { | |
218 | // Get track parameters in current AliMUONTrackParam | |
956019b6 | 219 | // from Geant3 parameters pointed to by "VGeant3", |
220 | // assumed to be calculated for forward motion in Z. | |
a9e2aefa | 221 | // "InverseBendingMomentum" is signed with "Charge". |
222 | this->fNonBendingCoor = VGeant3[0]; // X | |
223 | this->fBendingCoor = VGeant3[1]; // Y | |
224 | this->fZ = VGeant3[2]; // Z | |
225 | Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]); | |
226 | this->fInverseBendingMomentum = Charge / pYZ; | |
227 | this->fBendingSlope = VGeant3[4] / VGeant3[5]; | |
228 | this->fNonBendingSlope = VGeant3[3] / VGeant3[5]; | |
229 | } | |
230 | ||
231 | //__________________________________________________________________________ | |
232 | void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam) | |
233 | { | |
234 | // Track parameters extrapolated from current track parameters ("this") | |
235 | // to both chambers of the station(0..) "Station" | |
236 | // are returned in the array (dimension 2) of track parameters | |
237 | // pointed to by "TrackParam" (index 0 and 1 for first and second chambers). | |
238 | Double_t extZ[2], z1, z2; | |
ecfa008b | 239 | Int_t i1 = -1, i2 = -1; // = -1 to avoid compilation warnings |
a9e2aefa | 240 | AliMUON *pMUON = (AliMUON*) gAlice->GetModule("MUON"); // necessary ???? |
241 | // range of Station to be checked ???? | |
242 | z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber | |
243 | z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber | |
244 | // First and second Z to extrapolate at | |
245 | if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;} | |
246 | else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;} | |
247 | else { | |
248 | cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl; | |
249 | cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 << | |
250 | ") and z2 (" << z2 << ") of station(0..) " << Station << endl; | |
251 | } | |
252 | extZ[i1] = z1; | |
253 | extZ[i2] = z2; | |
254 | // copy of track parameters | |
255 | TrackParam[i1] = *this; | |
256 | // first extrapolation | |
257 | (&(TrackParam[i1]))->ExtrapToZ(extZ[0]); | |
258 | TrackParam[i2] = TrackParam[i1]; | |
259 | // second extrapolation | |
260 | (&(TrackParam[i2]))->ExtrapToZ(extZ[1]); | |
261 | return; | |
262 | } | |
263 | ||
04b5ea16 | 264 | //__________________________________________________________________________ |
265 | void AliMUONTrackParam::ExtrapToVertex() | |
266 | { | |
267 | // Extrapolation to the vertex. | |
268 | // Returns the track parameters resulting from the extrapolation, | |
269 | // in the current TrackParam. | |
956019b6 | 270 | // Changes parameters according to Branson correction through the absorber |
04b5ea16 | 271 | |
272 | Double_t zAbsorber = 503.0; // to be coherent with the Geant absorber geometry !!!! | |
273 | // Extrapolates track parameters upstream to the "Z" end of the front absorber | |
b45fd22b | 274 | ExtrapToZ(zAbsorber); // !!! |
04b5ea16 | 275 | // Makes Branson correction (multiple scattering + energy loss) |
276 | BransonCorrection(); | |
b45fd22b | 277 | // Makes a simple magnetic field correction through the absorber |
278 | FieldCorrection(zAbsorber); | |
04b5ea16 | 279 | } |
280 | ||
43af2cb6 | 281 | |
282 | // Keep this version for future developments | |
04b5ea16 | 283 | //__________________________________________________________________________ |
43af2cb6 | 284 | // void AliMUONTrackParam::BransonCorrection() |
285 | // { | |
286 | // // Branson correction of track parameters | |
287 | // // the entry parameters have to be calculated at the end of the absorber | |
288 | // Double_t zEndAbsorber, zBP, xBP, yBP; | |
289 | // Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta; | |
290 | // Int_t sign; | |
291 | // // Would it be possible to calculate all that from Geant configuration ???? | |
292 | // // and to get the Branson parameters from a function in ABSO module ???? | |
293 | // // with an eventual contribution from other detectors like START ???? | |
294 | // // Radiation lengths outer part theta > 3 degres | |
295 | // static Double_t x01[9] = { 18.8, // C (cm) | |
296 | // 10.397, // Concrete (cm) | |
297 | // 0.56, // Plomb (cm) | |
298 | // 47.26, // Polyethylene (cm) | |
299 | // 0.56, // Plomb (cm) | |
300 | // 47.26, // Polyethylene (cm) | |
301 | // 0.56, // Plomb (cm) | |
302 | // 47.26, // Polyethylene (cm) | |
303 | // 0.56 }; // Plomb (cm) | |
304 | // // inner part theta < 3 degres | |
305 | // static Double_t x02[3] = { 18.8, // C (cm) | |
306 | // 10.397, // Concrete (cm) | |
307 | // 0.35 }; // W (cm) | |
308 | // // z positions of the materials inside the absober outer part theta > 3 degres | |
309 | // static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 }; | |
310 | // // inner part theta < 3 degres | |
311 | // static Double_t z2[4] = { 90, 315, 467, 503 }; | |
312 | // static Bool_t first = kTRUE; | |
313 | // static Double_t zBP1, zBP2, rLimit; | |
314 | // // Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call) | |
315 | // if (first) { | |
316 | // first = kFALSE; | |
317 | // Double_t aNBP = 0.0; | |
318 | // Double_t aDBP = 0.0; | |
319 | // Int_t iBound; | |
320 | ||
321 | // for (iBound = 0; iBound < 9; iBound++) { | |
322 | // aNBP = aNBP + | |
323 | // (z1[iBound+1] * z1[iBound+1] * z1[iBound+1] - | |
324 | // z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound]; | |
325 | // aDBP = aDBP + | |
326 | // (z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound]; | |
327 | // } | |
328 | // zBP1 = (2.0 * aNBP) / (3.0 * aDBP); | |
329 | // aNBP = 0.0; | |
330 | // aDBP = 0.0; | |
331 | // for (iBound = 0; iBound < 3; iBound++) { | |
332 | // aNBP = aNBP + | |
333 | // (z2[iBound+1] * z2[iBound+1] * z2[iBound+1] - | |
334 | // z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound]; | |
335 | // aDBP = aDBP + | |
336 | // (z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound]; | |
337 | // } | |
338 | // zBP2 = (2.0 * aNBP) / (3.0 * aDBP); | |
339 | // rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.); | |
340 | // } | |
341 | ||
342 | // pYZ = TMath::Abs(1.0 / fInverseBendingMomentum); | |
343 | // sign = 1; | |
344 | // if (fInverseBendingMomentum < 0) sign = -1; | |
345 | // pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); | |
346 | // pX = pZ * fNonBendingSlope; | |
347 | // pY = pZ * fBendingSlope; | |
348 | // pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX); | |
349 | // xEndAbsorber = fNonBendingCoor; | |
350 | // yEndAbsorber = fBendingCoor; | |
351 | // radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber; | |
352 | ||
353 | // if (radiusEndAbsorber2 > rLimit*rLimit) { | |
354 | // zEndAbsorber = z1[9]; | |
355 | // zBP = zBP1; | |
356 | // } else { | |
357 | // zEndAbsorber = z2[3]; | |
358 | // zBP = zBP2; | |
359 | // } | |
360 | ||
361 | // xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP); | |
362 | // yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP); | |
363 | ||
364 | // // new parameters after Branson and energy loss corrections | |
365 | // pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP); | |
366 | // pX = pZ * xBP / zBP; | |
367 | // pY = pZ * yBP / zBP; | |
368 | // fBendingSlope = pY / pZ; | |
369 | // fNonBendingSlope = pX / pZ; | |
370 | ||
371 | // pT = TMath::Sqrt(pX * pX + pY * pY); | |
372 | // theta = TMath::ATan2(pT, pZ); | |
373 | // pTotal = | |
374 | // TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber); | |
375 | ||
376 | // fInverseBendingMomentum = (sign / pTotal) * | |
377 | // TMath::Sqrt(1.0 + | |
378 | // fBendingSlope * fBendingSlope + | |
379 | // fNonBendingSlope * fNonBendingSlope) / | |
380 | // TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope); | |
381 | ||
382 | // // vertex position at (0,0,0) | |
383 | // // should be taken from vertex measurement ??? | |
384 | // fBendingCoor = 0.0; | |
385 | // fNonBendingCoor = 0; | |
386 | // fZ= 0; | |
387 | // } | |
388 | ||
04b5ea16 | 389 | void AliMUONTrackParam::BransonCorrection() |
390 | { | |
391 | // Branson correction of track parameters | |
392 | // the entry parameters have to be calculated at the end of the absorber | |
43af2cb6 | 393 | // simplified version: the z positions of Branson's planes are no longer calculated |
394 | // but are given as inputs. One can use the macros MUONTestAbso.C and DrawTestAbso.C | |
395 | // to test this correction. | |
04b5ea16 | 396 | // Would it be possible to calculate all that from Geant configuration ???? |
956019b6 | 397 | // and to get the Branson parameters from a function in ABSO module ???? |
398 | // with an eventual contribution from other detectors like START ???? | |
43af2cb6 | 399 | Double_t zBP, xBP, yBP; |
400 | Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta; | |
401 | Int_t sign; | |
04b5ea16 | 402 | static Bool_t first = kTRUE; |
b45fd22b | 403 | static Double_t zBP1, zBP2, rLimit, thetaLimit, zEndAbsorber; |
43af2cb6 | 404 | // zBP1 for outer part and zBP2 for inner part (only at the first call) |
04b5ea16 | 405 | if (first) { |
406 | first = kFALSE; | |
43af2cb6 | 407 | |
408 | zEndAbsorber = 503; | |
b45fd22b | 409 | thetaLimit = 3.0 * (TMath::Pi()) / 180.; |
410 | rLimit = zEndAbsorber * TMath::Tan(thetaLimit); | |
411 | zBP1 = 450; // values close to those calculated with EvalAbso.C | |
43af2cb6 | 412 | zBP2 = 480; |
04b5ea16 | 413 | } |
414 | ||
415 | pYZ = TMath::Abs(1.0 / fInverseBendingMomentum); | |
416 | sign = 1; | |
417 | if (fInverseBendingMomentum < 0) sign = -1; | |
418 | pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); | |
419 | pX = pZ * fNonBendingSlope; | |
420 | pY = pZ * fBendingSlope; | |
421 | pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX); | |
422 | xEndAbsorber = fNonBendingCoor; | |
423 | yEndAbsorber = fBendingCoor; | |
424 | radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber; | |
425 | ||
426 | if (radiusEndAbsorber2 > rLimit*rLimit) { | |
04b5ea16 | 427 | zBP = zBP1; |
428 | } else { | |
04b5ea16 | 429 | zBP = zBP2; |
430 | } | |
431 | ||
432 | xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP); | |
433 | yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP); | |
434 | ||
435 | // new parameters after Branson and energy loss corrections | |
b45fd22b | 436 | // Float_t zSmear = zBP - gRandom->Gaus(0.,2.); // !!! possible smearing of Z vertex position |
437 | Float_t zSmear = zBP; | |
438 | ||
439 | pZ = pTotal * zSmear / TMath::Sqrt(xBP * xBP + yBP * yBP + zSmear * zSmear); | |
440 | pX = pZ * xBP / zSmear; | |
441 | pY = pZ * yBP / zSmear; | |
04b5ea16 | 442 | fBendingSlope = pY / pZ; |
443 | fNonBendingSlope = pX / pZ; | |
444 | ||
445 | pT = TMath::Sqrt(pX * pX + pY * pY); | |
446 | theta = TMath::ATan2(pT, pZ); | |
b45fd22b | 447 | pTotal = TotalMomentumEnergyLoss(thetaLimit, pTotal, theta); |
04b5ea16 | 448 | |
449 | fInverseBendingMomentum = (sign / pTotal) * | |
450 | TMath::Sqrt(1.0 + | |
451 | fBendingSlope * fBendingSlope + | |
452 | fNonBendingSlope * fNonBendingSlope) / | |
453 | TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope); | |
454 | ||
455 | // vertex position at (0,0,0) | |
456 | // should be taken from vertex measurement ??? | |
457 | fBendingCoor = 0.0; | |
458 | fNonBendingCoor = 0; | |
459 | fZ= 0; | |
460 | } | |
b45fd22b | 461 | |
04b5ea16 | 462 | //__________________________________________________________________________ |
b45fd22b | 463 | Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t thetaLimit, Double_t pTotal, Double_t theta) |
04b5ea16 | 464 | { |
465 | // Returns the total momentum corrected from energy loss in the front absorber | |
43af2cb6 | 466 | // One can use the macros MUONTestAbso.C and DrawTestAbso.C |
467 | // to test this correction. | |
b45fd22b | 468 | // Momentum energy loss behaviour evaluated with the simulation of single muons (april 2002) |
04b5ea16 | 469 | Double_t deltaP, pTotalCorrected; |
470 | ||
b45fd22b | 471 | // Parametrization to be redone according to change of absorber material ???? |
956019b6 | 472 | // See remark in function BransonCorrection !!!! |
04b5ea16 | 473 | // The name is not so good, and there are many arguments !!!! |
b45fd22b | 474 | if (theta < thetaLimit ) { |
475 | if (pTotal < 20) { | |
476 | deltaP = 2.5938 + 0.0570 * pTotal - 0.001151 * pTotal * pTotal; | |
04b5ea16 | 477 | } else { |
b45fd22b | 478 | deltaP = 3.0714 + 0.011767 *pTotal; |
04b5ea16 | 479 | } |
480 | } else { | |
b45fd22b | 481 | if (pTotal < 20) { |
482 | deltaP = 2.1207 + 0.05478 * pTotal - 0.00145079 * pTotal * pTotal; | |
04b5ea16 | 483 | } else { |
b45fd22b | 484 | deltaP = 2.6069 + 0.0051705 * pTotal; |
04b5ea16 | 485 | } |
486 | } | |
487 | pTotalCorrected = pTotal + deltaP / TMath::Cos(theta); | |
488 | return pTotalCorrected; | |
489 | } | |
490 | ||
b45fd22b | 491 | //__________________________________________________________________________ |
492 | void AliMUONTrackParam::FieldCorrection(Double_t Z) | |
493 | { | |
494 | // | |
495 | // Correction of the effect of the magnetic field in the absorber | |
496 | // Assume a constant field along Z axis. | |
497 | ||
498 | Float_t b[3],x[3]; | |
499 | Double_t bZ; | |
500 | Double_t pYZ,pX,pY,pZ,pT; | |
501 | Double_t pXNew,pYNew; | |
502 | Double_t c; | |
503 | ||
504 | pYZ = TMath::Abs(1.0 / fInverseBendingMomentum); | |
505 | c = TMath::Sign(1.0,fInverseBendingMomentum); // particle charge | |
506 | ||
507 | pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); | |
508 | pX = pZ * fNonBendingSlope; | |
509 | pY = pZ * fBendingSlope; | |
510 | pT = TMath::Sqrt(pX*pX+pY*pY); | |
511 | ||
512 | if (pZ <= 0) return; | |
513 | x[2] = Z/2; | |
514 | x[0] = x[2]*fNonBendingSlope; | |
515 | x[1] = x[2]*fBendingSlope; | |
516 | ||
517 | // Take magn. field value at position x. | |
518 | gAlice->Field()->Field(x, b); | |
519 | bZ = b[2]; | |
520 | ||
521 | // Transverse momentum rotation | |
522 | // Parameterized with the study of DeltaPhi = phiReco - phiGen as a function of pZ. | |
523 | Double_t phiShift = c*0.436*0.0003*bZ*Z/pZ; | |
524 | ||
525 | // Rotate momentum around Z axis. | |
526 | pXNew = pX*TMath::Cos(phiShift) - pY*TMath::Sin(phiShift); | |
527 | pYNew = pX*TMath::Sin(phiShift) + pY*TMath::Cos(phiShift); | |
528 | ||
529 | fBendingSlope = pYNew / pZ; | |
530 | fNonBendingSlope = pXNew / pZ; | |
531 | ||
532 | fInverseBendingMomentum = c / TMath::Sqrt(pYNew*pYNew+pZ*pZ); | |
533 | ||
534 | } |