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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 | ||
88cb7938 | 16 | /* $Id$ */ |
a9e2aefa | 17 | |
3831f268 | 18 | /////////////////////////////////////////////////// |
19 | // | |
20 | // Track parameters | |
21 | // in | |
22 | // ALICE | |
23 | // dimuon | |
24 | // spectrometer | |
a9e2aefa | 25 | // |
3831f268 | 26 | /////////////////////////////////////////////////// |
a9e2aefa | 27 | |
70479d0e | 28 | #include <Riostream.h> |
a9e2aefa | 29 | |
30 | #include "AliCallf77.h" | |
3831f268 | 31 | #include "AliMUON.h" |
a9e2aefa | 32 | #include "AliMUONTrackParam.h" |
3831f268 | 33 | #include "AliMUONChamber.h" |
a9e2aefa | 34 | #include "AliRun.h" |
94de3818 | 35 | #include "AliMagF.h" |
a9e2aefa | 36 | |
37 | ClassImp(AliMUONTrackParam) // Class implementation in ROOT context | |
38 | ||
a6f03ddb | 39 | // A few calls in Fortran or from Fortran (extrap.F). |
40 | // Needed, instead of calls to Geant subroutines, | |
41 | // because double precision is necessary for track fit converging with Minuit. | |
42 | // The "extrap" functions should be translated into C++ ???? | |
a9e2aefa | 43 | #ifndef WIN32 |
a6f03ddb | 44 | # define extrap_onestep_helix extrap_onestep_helix_ |
45 | # define extrap_onestep_helix3 extrap_onestep_helix3_ | |
46 | # define extrap_onestep_rungekutta extrap_onestep_rungekutta_ | |
47 | # define gufld_double gufld_double_ | |
a9e2aefa | 48 | #else |
a6f03ddb | 49 | # define extrap_onestep_helix EXTRAP_ONESTEP_HELIX |
50 | # define extrap_onestep_helix3 EXTRAP_ONESTEP_HELIX3 | |
51 | # define extrap_onestep_rungekutta EXTRAP_ONESTEP_RUNGEKUTTA | |
52 | # define gufld_double GUFLD_DOUBLE | |
a9e2aefa | 53 | #endif |
54 | ||
a6f03ddb | 55 | extern "C" { |
56 | void type_of_call extrap_onestep_helix | |
57 | (Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New); | |
58 | ||
59 | void type_of_call extrap_onestep_helix3 | |
60 | (Double_t &Field, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New); | |
61 | ||
62 | void type_of_call extrap_onestep_rungekutta | |
63 | (Double_t &Charge, Double_t &StepLength, Double_t *VGeant3, Double_t *VGeant3New); | |
64 | ||
65 | void type_of_call gufld_double(Double_t *Position, Double_t *Field) { | |
66 | // interface to "gAlice->Field()->Field" for arguments in double precision | |
67 | Float_t x[3], b[3]; | |
68 | x[0] = Position[0]; x[1] = Position[1]; x[2] = Position[2]; | |
69 | gAlice->Field()->Field(x, b); | |
70 | Field[0] = b[0]; Field[1] = b[1]; Field[2] = b[2]; | |
71 | } | |
a9e2aefa | 72 | } |
73 | ||
a9e2aefa | 74 | //__________________________________________________________________________ |
75 | void AliMUONTrackParam::ExtrapToZ(Double_t Z) | |
76 | { | |
77 | // Track parameter extrapolation to the plane at "Z". | |
78 | // On return, the track parameters resulting from the extrapolation | |
79 | // replace the current track parameters. | |
a9e2aefa | 80 | if (this->fZ == Z) return; // nothing to be done if same Z |
81 | Double_t forwardBackward; // +1 if forward, -1 if backward | |
5b64e914 | 82 | if (Z < this->fZ) forwardBackward = 1.0; // spectro. z<0 |
a9e2aefa | 83 | else forwardBackward = -1.0; |
a6f03ddb | 84 | Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ???? |
a9e2aefa | 85 | Int_t iGeant3, stepNumber; |
86 | Int_t maxStepNumber = 5000; // in parameter ???? | |
87 | // For safety: return kTRUE or kFALSE ???? | |
a6f03ddb | 88 | // Parameter vector for calling EXTRAP_ONESTEP |
a9e2aefa | 89 | SetGeant3Parameters(vGeant3, forwardBackward); |
956019b6 | 90 | // sign of charge (sign of fInverseBendingMomentum if forward motion) |
a6f03ddb | 91 | // must be changed if backward extrapolation |
956019b6 | 92 | Double_t chargeExtrap = forwardBackward * |
93 | TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum); | |
a9e2aefa | 94 | Double_t stepLength = 6.0; // in parameter ???? |
95 | // Extrapolation loop | |
96 | stepNumber = 0; | |
5b64e914 | 97 | while (((-forwardBackward * (vGeant3[2] - Z)) <= 0.0) && // spectro. z<0 |
a9e2aefa | 98 | (stepNumber < maxStepNumber)) { |
99 | stepNumber++; | |
a6f03ddb | 100 | // Option for switching between helix and Runge-Kutta ???? |
101 | // extrap_onestep_rungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New); | |
102 | extrap_onestep_helix(chargeExtrap, stepLength, vGeant3, vGeant3New); | |
5b64e914 | 103 | if ((-forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z spectro. z<0 |
a9e2aefa | 104 | // better use TArray ???? |
105 | for (iGeant3 = 0; iGeant3 < 7; iGeant3++) | |
106 | {vGeant3[iGeant3] = vGeant3New[iGeant3];} | |
107 | } | |
108 | // check maxStepNumber ???? | |
a9e2aefa | 109 | // Interpolation back to exact Z (2nd order) |
110 | // should be in function ???? using TArray ???? | |
111 | Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2 | |
112 | Double_t dZ1i = Z - vGeant3[2]; // 1-i | |
113 | Double_t dZi2 = vGeant3New[2] - Z; // i->2 | |
114 | Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12; | |
115 | Double_t xSecond = | |
116 | ((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12; | |
117 | Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12; | |
118 | Double_t ySecond = | |
119 | ((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12; | |
120 | vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X | |
121 | vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y | |
122 | vGeant3[2] = Z; // Z | |
123 | Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i); | |
124 | Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i); | |
956019b6 | 125 | // (PX, PY, PZ)/PTOT assuming forward motion |
a9e2aefa | 126 | vGeant3[5] = |
127 | 1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT | |
128 | vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT | |
129 | vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT | |
956019b6 | 130 | // Track parameters from Geant3 parameters, |
131 | // with charge back for forward motion | |
132 | GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward); | |
a9e2aefa | 133 | } |
134 | ||
135 | //__________________________________________________________________________ | |
136 | void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward) | |
137 | { | |
138 | // Set vector of Geant3 parameters pointed to by "VGeant3" | |
139 | // from track parameters in current AliMUONTrackParam. | |
140 | // Since AliMUONTrackParam is only geometry, one uses "ForwardBackward" | |
141 | // to know whether the particle is going forward (+1) or backward (-1). | |
142 | VGeant3[0] = this->fNonBendingCoor; // X | |
143 | VGeant3[1] = this->fBendingCoor; // Y | |
144 | VGeant3[2] = this->fZ; // Z | |
145 | Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum); | |
146 | Double_t pZ = | |
147 | pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope); | |
148 | VGeant3[6] = | |
149 | TMath::Sqrt(pYZ * pYZ + | |
150 | pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT | |
5b64e914 | 151 | VGeant3[5] = -ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT spectro. z<0 |
a9e2aefa | 152 | VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT |
153 | VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT | |
154 | } | |
155 | ||
156 | //__________________________________________________________________________ | |
157 | void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge) | |
158 | { | |
159 | // Get track parameters in current AliMUONTrackParam | |
956019b6 | 160 | // from Geant3 parameters pointed to by "VGeant3", |
161 | // assumed to be calculated for forward motion in Z. | |
a9e2aefa | 162 | // "InverseBendingMomentum" is signed with "Charge". |
163 | this->fNonBendingCoor = VGeant3[0]; // X | |
164 | this->fBendingCoor = VGeant3[1]; // Y | |
165 | this->fZ = VGeant3[2]; // Z | |
166 | Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]); | |
167 | this->fInverseBendingMomentum = Charge / pYZ; | |
168 | this->fBendingSlope = VGeant3[4] / VGeant3[5]; | |
169 | this->fNonBendingSlope = VGeant3[3] / VGeant3[5]; | |
170 | } | |
171 | ||
172 | //__________________________________________________________________________ | |
173 | void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam) | |
174 | { | |
175 | // Track parameters extrapolated from current track parameters ("this") | |
176 | // to both chambers of the station(0..) "Station" | |
177 | // are returned in the array (dimension 2) of track parameters | |
178 | // pointed to by "TrackParam" (index 0 and 1 for first and second chambers). | |
179 | Double_t extZ[2], z1, z2; | |
ecfa008b | 180 | Int_t i1 = -1, i2 = -1; // = -1 to avoid compilation warnings |
a9e2aefa | 181 | AliMUON *pMUON = (AliMUON*) gAlice->GetModule("MUON"); // necessary ???? |
182 | // range of Station to be checked ???? | |
183 | z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber | |
184 | z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber | |
185 | // First and second Z to extrapolate at | |
186 | if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;} | |
187 | else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;} | |
188 | else { | |
189 | cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl; | |
190 | cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 << | |
191 | ") and z2 (" << z2 << ") of station(0..) " << Station << endl; | |
192 | } | |
193 | extZ[i1] = z1; | |
194 | extZ[i2] = z2; | |
195 | // copy of track parameters | |
196 | TrackParam[i1] = *this; | |
197 | // first extrapolation | |
198 | (&(TrackParam[i1]))->ExtrapToZ(extZ[0]); | |
199 | TrackParam[i2] = TrackParam[i1]; | |
200 | // second extrapolation | |
201 | (&(TrackParam[i2]))->ExtrapToZ(extZ[1]); | |
202 | return; | |
203 | } | |
204 | ||
04b5ea16 | 205 | //__________________________________________________________________________ |
206 | void AliMUONTrackParam::ExtrapToVertex() | |
207 | { | |
208 | // Extrapolation to the vertex. | |
209 | // Returns the track parameters resulting from the extrapolation, | |
210 | // in the current TrackParam. | |
956019b6 | 211 | // Changes parameters according to Branson correction through the absorber |
04b5ea16 | 212 | |
5b64e914 | 213 | Double_t zAbsorber = -503.0; // to be coherent with the Geant absorber geometry !!!! |
214 | // spectro. (z<0) | |
04b5ea16 | 215 | // Extrapolates track parameters upstream to the "Z" end of the front absorber |
b45fd22b | 216 | ExtrapToZ(zAbsorber); // !!! |
5b64e914 | 217 | // Makes Branson correction (multiple scattering + energy loss) |
04b5ea16 | 218 | BransonCorrection(); |
5b64e914 | 219 | // Makes a simple magnetic field correction through the absorber |
b45fd22b | 220 | FieldCorrection(zAbsorber); |
04b5ea16 | 221 | } |
222 | ||
43af2cb6 | 223 | |
224 | // Keep this version for future developments | |
04b5ea16 | 225 | //__________________________________________________________________________ |
43af2cb6 | 226 | // void AliMUONTrackParam::BransonCorrection() |
227 | // { | |
228 | // // Branson correction of track parameters | |
229 | // // the entry parameters have to be calculated at the end of the absorber | |
230 | // Double_t zEndAbsorber, zBP, xBP, yBP; | |
231 | // Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta; | |
232 | // Int_t sign; | |
233 | // // Would it be possible to calculate all that from Geant configuration ???? | |
234 | // // and to get the Branson parameters from a function in ABSO module ???? | |
235 | // // with an eventual contribution from other detectors like START ???? | |
236 | // // Radiation lengths outer part theta > 3 degres | |
237 | // static Double_t x01[9] = { 18.8, // C (cm) | |
238 | // 10.397, // Concrete (cm) | |
239 | // 0.56, // Plomb (cm) | |
240 | // 47.26, // Polyethylene (cm) | |
241 | // 0.56, // Plomb (cm) | |
242 | // 47.26, // Polyethylene (cm) | |
243 | // 0.56, // Plomb (cm) | |
244 | // 47.26, // Polyethylene (cm) | |
245 | // 0.56 }; // Plomb (cm) | |
246 | // // inner part theta < 3 degres | |
247 | // static Double_t x02[3] = { 18.8, // C (cm) | |
248 | // 10.397, // Concrete (cm) | |
249 | // 0.35 }; // W (cm) | |
250 | // // z positions of the materials inside the absober outer part theta > 3 degres | |
251 | // static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 }; | |
252 | // // inner part theta < 3 degres | |
253 | // static Double_t z2[4] = { 90, 315, 467, 503 }; | |
254 | // static Bool_t first = kTRUE; | |
255 | // static Double_t zBP1, zBP2, rLimit; | |
256 | // // Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call) | |
257 | // if (first) { | |
258 | // first = kFALSE; | |
259 | // Double_t aNBP = 0.0; | |
260 | // Double_t aDBP = 0.0; | |
261 | // Int_t iBound; | |
262 | ||
263 | // for (iBound = 0; iBound < 9; iBound++) { | |
264 | // aNBP = aNBP + | |
265 | // (z1[iBound+1] * z1[iBound+1] * z1[iBound+1] - | |
266 | // z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound]; | |
267 | // aDBP = aDBP + | |
268 | // (z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound]; | |
269 | // } | |
270 | // zBP1 = (2.0 * aNBP) / (3.0 * aDBP); | |
271 | // aNBP = 0.0; | |
272 | // aDBP = 0.0; | |
273 | // for (iBound = 0; iBound < 3; iBound++) { | |
274 | // aNBP = aNBP + | |
275 | // (z2[iBound+1] * z2[iBound+1] * z2[iBound+1] - | |
276 | // z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound]; | |
277 | // aDBP = aDBP + | |
278 | // (z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound]; | |
279 | // } | |
280 | // zBP2 = (2.0 * aNBP) / (3.0 * aDBP); | |
281 | // rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.); | |
282 | // } | |
283 | ||
284 | // pYZ = TMath::Abs(1.0 / fInverseBendingMomentum); | |
285 | // sign = 1; | |
286 | // if (fInverseBendingMomentum < 0) sign = -1; | |
287 | // pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); | |
288 | // pX = pZ * fNonBendingSlope; | |
289 | // pY = pZ * fBendingSlope; | |
290 | // pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX); | |
291 | // xEndAbsorber = fNonBendingCoor; | |
292 | // yEndAbsorber = fBendingCoor; | |
293 | // radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber; | |
294 | ||
295 | // if (radiusEndAbsorber2 > rLimit*rLimit) { | |
296 | // zEndAbsorber = z1[9]; | |
297 | // zBP = zBP1; | |
298 | // } else { | |
299 | // zEndAbsorber = z2[3]; | |
300 | // zBP = zBP2; | |
301 | // } | |
302 | ||
303 | // xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP); | |
304 | // yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP); | |
305 | ||
306 | // // new parameters after Branson and energy loss corrections | |
307 | // pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP); | |
308 | // pX = pZ * xBP / zBP; | |
309 | // pY = pZ * yBP / zBP; | |
310 | // fBendingSlope = pY / pZ; | |
311 | // fNonBendingSlope = pX / pZ; | |
312 | ||
313 | // pT = TMath::Sqrt(pX * pX + pY * pY); | |
314 | // theta = TMath::ATan2(pT, pZ); | |
315 | // pTotal = | |
316 | // TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber); | |
317 | ||
318 | // fInverseBendingMomentum = (sign / pTotal) * | |
319 | // TMath::Sqrt(1.0 + | |
320 | // fBendingSlope * fBendingSlope + | |
321 | // fNonBendingSlope * fNonBendingSlope) / | |
322 | // TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope); | |
323 | ||
324 | // // vertex position at (0,0,0) | |
325 | // // should be taken from vertex measurement ??? | |
326 | // fBendingCoor = 0.0; | |
327 | // fNonBendingCoor = 0; | |
328 | // fZ= 0; | |
329 | // } | |
330 | ||
04b5ea16 | 331 | void AliMUONTrackParam::BransonCorrection() |
332 | { | |
333 | // Branson correction of track parameters | |
334 | // the entry parameters have to be calculated at the end of the absorber | |
43af2cb6 | 335 | // simplified version: the z positions of Branson's planes are no longer calculated |
336 | // but are given as inputs. One can use the macros MUONTestAbso.C and DrawTestAbso.C | |
337 | // to test this correction. | |
04b5ea16 | 338 | // Would it be possible to calculate all that from Geant configuration ???? |
956019b6 | 339 | // and to get the Branson parameters from a function in ABSO module ???? |
340 | // with an eventual contribution from other detectors like START ???? | |
43af2cb6 | 341 | Double_t zBP, xBP, yBP; |
342 | Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta; | |
343 | Int_t sign; | |
04b5ea16 | 344 | static Bool_t first = kTRUE; |
b45fd22b | 345 | static Double_t zBP1, zBP2, rLimit, thetaLimit, zEndAbsorber; |
43af2cb6 | 346 | // zBP1 for outer part and zBP2 for inner part (only at the first call) |
04b5ea16 | 347 | if (first) { |
348 | first = kFALSE; | |
43af2cb6 | 349 | |
5b64e914 | 350 | zEndAbsorber = -503; // spectro (z<0) |
b45fd22b | 351 | thetaLimit = 3.0 * (TMath::Pi()) / 180.; |
5b64e914 | 352 | rLimit = TMath::Abs(zEndAbsorber) * TMath::Tan(thetaLimit); |
353 | zBP1 = -450; // values close to those calculated with EvalAbso.C | |
354 | zBP2 = -480; | |
04b5ea16 | 355 | } |
356 | ||
357 | pYZ = TMath::Abs(1.0 / fInverseBendingMomentum); | |
358 | sign = 1; | |
359 | if (fInverseBendingMomentum < 0) sign = -1; | |
5b64e914 | 360 | pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro (z<0) |
04b5ea16 | 361 | pX = pZ * fNonBendingSlope; |
362 | pY = pZ * fBendingSlope; | |
363 | pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX); | |
364 | xEndAbsorber = fNonBendingCoor; | |
365 | yEndAbsorber = fBendingCoor; | |
366 | radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber; | |
367 | ||
368 | if (radiusEndAbsorber2 > rLimit*rLimit) { | |
04b5ea16 | 369 | zBP = zBP1; |
370 | } else { | |
04b5ea16 | 371 | zBP = zBP2; |
372 | } | |
373 | ||
374 | xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP); | |
375 | yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP); | |
376 | ||
377 | // new parameters after Branson and energy loss corrections | |
b45fd22b | 378 | // Float_t zSmear = zBP - gRandom->Gaus(0.,2.); // !!! possible smearing of Z vertex position |
379 | Float_t zSmear = zBP; | |
380 | ||
381 | pZ = pTotal * zSmear / TMath::Sqrt(xBP * xBP + yBP * yBP + zSmear * zSmear); | |
382 | pX = pZ * xBP / zSmear; | |
383 | pY = pZ * yBP / zSmear; | |
04b5ea16 | 384 | fBendingSlope = pY / pZ; |
385 | fNonBendingSlope = pX / pZ; | |
5b64e914 | 386 | |
04b5ea16 | 387 | |
388 | pT = TMath::Sqrt(pX * pX + pY * pY); | |
5b64e914 | 389 | theta = TMath::ATan2(pT, TMath::Abs(pZ)); |
b45fd22b | 390 | pTotal = TotalMomentumEnergyLoss(thetaLimit, pTotal, theta); |
04b5ea16 | 391 | |
392 | fInverseBendingMomentum = (sign / pTotal) * | |
393 | TMath::Sqrt(1.0 + | |
394 | fBendingSlope * fBendingSlope + | |
395 | fNonBendingSlope * fNonBendingSlope) / | |
396 | TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope); | |
397 | ||
398 | // vertex position at (0,0,0) | |
399 | // should be taken from vertex measurement ??? | |
400 | fBendingCoor = 0.0; | |
401 | fNonBendingCoor = 0; | |
402 | fZ= 0; | |
403 | } | |
b45fd22b | 404 | |
04b5ea16 | 405 | //__________________________________________________________________________ |
b45fd22b | 406 | Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t thetaLimit, Double_t pTotal, Double_t theta) |
04b5ea16 | 407 | { |
408 | // Returns the total momentum corrected from energy loss in the front absorber | |
43af2cb6 | 409 | // One can use the macros MUONTestAbso.C and DrawTestAbso.C |
410 | // to test this correction. | |
b45fd22b | 411 | // Momentum energy loss behaviour evaluated with the simulation of single muons (april 2002) |
04b5ea16 | 412 | Double_t deltaP, pTotalCorrected; |
413 | ||
b45fd22b | 414 | // Parametrization to be redone according to change of absorber material ???? |
956019b6 | 415 | // See remark in function BransonCorrection !!!! |
04b5ea16 | 416 | // The name is not so good, and there are many arguments !!!! |
b45fd22b | 417 | if (theta < thetaLimit ) { |
418 | if (pTotal < 20) { | |
419 | deltaP = 2.5938 + 0.0570 * pTotal - 0.001151 * pTotal * pTotal; | |
04b5ea16 | 420 | } else { |
b45fd22b | 421 | deltaP = 3.0714 + 0.011767 *pTotal; |
04b5ea16 | 422 | } |
423 | } else { | |
b45fd22b | 424 | if (pTotal < 20) { |
425 | deltaP = 2.1207 + 0.05478 * pTotal - 0.00145079 * pTotal * pTotal; | |
04b5ea16 | 426 | } else { |
b45fd22b | 427 | deltaP = 2.6069 + 0.0051705 * pTotal; |
04b5ea16 | 428 | } |
429 | } | |
430 | pTotalCorrected = pTotal + deltaP / TMath::Cos(theta); | |
431 | return pTotalCorrected; | |
432 | } | |
433 | ||
b45fd22b | 434 | //__________________________________________________________________________ |
435 | void AliMUONTrackParam::FieldCorrection(Double_t Z) | |
436 | { | |
437 | // | |
438 | // Correction of the effect of the magnetic field in the absorber | |
439 | // Assume a constant field along Z axis. | |
440 | ||
441 | Float_t b[3],x[3]; | |
442 | Double_t bZ; | |
443 | Double_t pYZ,pX,pY,pZ,pT; | |
444 | Double_t pXNew,pYNew; | |
445 | Double_t c; | |
446 | ||
447 | pYZ = TMath::Abs(1.0 / fInverseBendingMomentum); | |
448 | c = TMath::Sign(1.0,fInverseBendingMomentum); // particle charge | |
449 | ||
5b64e914 | 450 | pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0) |
b45fd22b | 451 | pX = pZ * fNonBendingSlope; |
452 | pY = pZ * fBendingSlope; | |
453 | pT = TMath::Sqrt(pX*pX+pY*pY); | |
454 | ||
5b64e914 | 455 | if (TMath::Abs(pZ) <= 0) return; |
b45fd22b | 456 | x[2] = Z/2; |
457 | x[0] = x[2]*fNonBendingSlope; | |
458 | x[1] = x[2]*fBendingSlope; | |
459 | ||
460 | // Take magn. field value at position x. | |
461 | gAlice->Field()->Field(x, b); | |
462 | bZ = b[2]; | |
463 | ||
464 | // Transverse momentum rotation | |
465 | // Parameterized with the study of DeltaPhi = phiReco - phiGen as a function of pZ. | |
5b64e914 | 466 | Double_t phiShift = c*0.436*0.0003*bZ*Z/pZ; |
b45fd22b | 467 | // Rotate momentum around Z axis. |
468 | pXNew = pX*TMath::Cos(phiShift) - pY*TMath::Sin(phiShift); | |
469 | pYNew = pX*TMath::Sin(phiShift) + pY*TMath::Cos(phiShift); | |
470 | ||
471 | fBendingSlope = pYNew / pZ; | |
472 | fNonBendingSlope = pXNew / pZ; | |
473 | ||
474 | fInverseBendingMomentum = c / TMath::Sqrt(pYNew*pYNew+pZ*pZ); | |
475 | ||
476 | } |