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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 | } |
30178c30 | 73 | |
61adb9bd | 74 | //_________________________________________________________________________ |
30178c30 | 75 | AliMUONTrackParam::AliMUONTrackParam() |
76 | : TObject() | |
77 | { | |
78 | // Constructor | |
79 | ||
80 | fInverseBendingMomentum = 0; | |
81 | fBendingSlope = 0; | |
82 | fNonBendingSlope = 0; | |
83 | fZ = 0; | |
84 | fBendingCoor = 0; | |
85 | fNonBendingCoor = 0; | |
86 | } | |
61adb9bd | 87 | |
30178c30 | 88 | //_________________________________________________________________________ |
89 | AliMUONTrackParam& | |
90 | AliMUONTrackParam::operator=(const AliMUONTrackParam& theMUONTrackParam) | |
61adb9bd | 91 | { |
30178c30 | 92 | if (this == &theMUONTrackParam) |
61adb9bd | 93 | return *this; |
94 | ||
30178c30 | 95 | // base class assignement |
96 | TObject::operator=(theMUONTrackParam); | |
97 | ||
98 | fInverseBendingMomentum = theMUONTrackParam.fInverseBendingMomentum; | |
99 | fBendingSlope = theMUONTrackParam.fBendingSlope; | |
100 | fNonBendingSlope = theMUONTrackParam.fNonBendingSlope; | |
101 | fZ = theMUONTrackParam.fZ; | |
102 | fBendingCoor = theMUONTrackParam.fBendingCoor; | |
103 | fNonBendingCoor = theMUONTrackParam.fNonBendingCoor; | |
61adb9bd | 104 | |
105 | return *this; | |
106 | } | |
107 | //_________________________________________________________________________ | |
30178c30 | 108 | AliMUONTrackParam::AliMUONTrackParam(const AliMUONTrackParam& theMUONTrackParam) |
109 | : TObject(theMUONTrackParam) | |
61adb9bd | 110 | { |
30178c30 | 111 | fInverseBendingMomentum = theMUONTrackParam.fInverseBendingMomentum; |
112 | fBendingSlope = theMUONTrackParam.fBendingSlope; | |
113 | fNonBendingSlope = theMUONTrackParam.fNonBendingSlope; | |
114 | fZ = theMUONTrackParam.fZ; | |
115 | fBendingCoor = theMUONTrackParam.fBendingCoor; | |
116 | fNonBendingCoor = theMUONTrackParam.fNonBendingCoor; | |
61adb9bd | 117 | } |
a9e2aefa | 118 | |
a9e2aefa | 119 | //__________________________________________________________________________ |
120 | void AliMUONTrackParam::ExtrapToZ(Double_t Z) | |
121 | { | |
122 | // Track parameter extrapolation to the plane at "Z". | |
123 | // On return, the track parameters resulting from the extrapolation | |
124 | // replace the current track parameters. | |
a9e2aefa | 125 | if (this->fZ == Z) return; // nothing to be done if same Z |
126 | Double_t forwardBackward; // +1 if forward, -1 if backward | |
5b64e914 | 127 | if (Z < this->fZ) forwardBackward = 1.0; // spectro. z<0 |
a9e2aefa | 128 | else forwardBackward = -1.0; |
a6f03ddb | 129 | Double_t vGeant3[7], vGeant3New[7]; // 7 in parameter ???? |
a9e2aefa | 130 | Int_t iGeant3, stepNumber; |
131 | Int_t maxStepNumber = 5000; // in parameter ???? | |
132 | // For safety: return kTRUE or kFALSE ???? | |
a6f03ddb | 133 | // Parameter vector for calling EXTRAP_ONESTEP |
a9e2aefa | 134 | SetGeant3Parameters(vGeant3, forwardBackward); |
956019b6 | 135 | // sign of charge (sign of fInverseBendingMomentum if forward motion) |
a6f03ddb | 136 | // must be changed if backward extrapolation |
956019b6 | 137 | Double_t chargeExtrap = forwardBackward * |
138 | TMath::Sign(Double_t(1.0), this->fInverseBendingMomentum); | |
a9e2aefa | 139 | Double_t stepLength = 6.0; // in parameter ???? |
140 | // Extrapolation loop | |
141 | stepNumber = 0; | |
5b64e914 | 142 | while (((-forwardBackward * (vGeant3[2] - Z)) <= 0.0) && // spectro. z<0 |
a9e2aefa | 143 | (stepNumber < maxStepNumber)) { |
144 | stepNumber++; | |
a6f03ddb | 145 | // Option for switching between helix and Runge-Kutta ???? |
146 | // extrap_onestep_rungekutta(chargeExtrap, stepLength, vGeant3, vGeant3New); | |
147 | extrap_onestep_helix(chargeExtrap, stepLength, vGeant3, vGeant3New); | |
5b64e914 | 148 | if ((-forwardBackward * (vGeant3New[2] - Z)) > 0.0) break; // one is beyond Z spectro. z<0 |
a9e2aefa | 149 | // better use TArray ???? |
150 | for (iGeant3 = 0; iGeant3 < 7; iGeant3++) | |
151 | {vGeant3[iGeant3] = vGeant3New[iGeant3];} | |
152 | } | |
153 | // check maxStepNumber ???? | |
a9e2aefa | 154 | // Interpolation back to exact Z (2nd order) |
155 | // should be in function ???? using TArray ???? | |
156 | Double_t dZ12 = vGeant3New[2] - vGeant3[2]; // 1->2 | |
157 | Double_t dZ1i = Z - vGeant3[2]; // 1-i | |
158 | Double_t dZi2 = vGeant3New[2] - Z; // i->2 | |
159 | Double_t xPrime = (vGeant3New[0] - vGeant3[0]) / dZ12; | |
160 | Double_t xSecond = | |
161 | ((vGeant3New[3] / vGeant3New[5]) - (vGeant3[3] / vGeant3[5])) / dZ12; | |
162 | Double_t yPrime = (vGeant3New[1] - vGeant3[1]) / dZ12; | |
163 | Double_t ySecond = | |
164 | ((vGeant3New[4] / vGeant3New[5]) - (vGeant3[4] / vGeant3[5])) / dZ12; | |
165 | vGeant3[0] = vGeant3[0] + xPrime * dZ1i - 0.5 * xSecond * dZ1i * dZi2; // X | |
166 | vGeant3[1] = vGeant3[1] + yPrime * dZ1i - 0.5 * ySecond * dZ1i * dZi2; // Y | |
167 | vGeant3[2] = Z; // Z | |
168 | Double_t xPrimeI = xPrime - 0.5 * xSecond * (dZi2 - dZ1i); | |
169 | Double_t yPrimeI = yPrime - 0.5 * ySecond * (dZi2 - dZ1i); | |
956019b6 | 170 | // (PX, PY, PZ)/PTOT assuming forward motion |
a9e2aefa | 171 | vGeant3[5] = |
172 | 1.0 / TMath::Sqrt(1.0 + xPrimeI * xPrimeI + yPrimeI * yPrimeI); // PZ/PTOT | |
173 | vGeant3[3] = xPrimeI * vGeant3[5]; // PX/PTOT | |
174 | vGeant3[4] = yPrimeI * vGeant3[5]; // PY/PTOT | |
956019b6 | 175 | // Track parameters from Geant3 parameters, |
176 | // with charge back for forward motion | |
177 | GetFromGeant3Parameters(vGeant3, chargeExtrap * forwardBackward); | |
a9e2aefa | 178 | } |
179 | ||
180 | //__________________________________________________________________________ | |
181 | void AliMUONTrackParam::SetGeant3Parameters(Double_t *VGeant3, Double_t ForwardBackward) | |
182 | { | |
183 | // Set vector of Geant3 parameters pointed to by "VGeant3" | |
184 | // from track parameters in current AliMUONTrackParam. | |
185 | // Since AliMUONTrackParam is only geometry, one uses "ForwardBackward" | |
186 | // to know whether the particle is going forward (+1) or backward (-1). | |
187 | VGeant3[0] = this->fNonBendingCoor; // X | |
188 | VGeant3[1] = this->fBendingCoor; // Y | |
189 | VGeant3[2] = this->fZ; // Z | |
190 | Double_t pYZ = TMath::Abs(1.0 / this->fInverseBendingMomentum); | |
191 | Double_t pZ = | |
192 | pYZ / TMath::Sqrt(1.0 + this->fBendingSlope * this->fBendingSlope); | |
193 | VGeant3[6] = | |
194 | TMath::Sqrt(pYZ * pYZ + | |
195 | pZ * pZ * this->fNonBendingSlope * this->fNonBendingSlope); // PTOT | |
5b64e914 | 196 | VGeant3[5] = -ForwardBackward * pZ / VGeant3[6]; // PZ/PTOT spectro. z<0 |
a9e2aefa | 197 | VGeant3[3] = this->fNonBendingSlope * VGeant3[5]; // PX/PTOT |
198 | VGeant3[4] = this->fBendingSlope * VGeant3[5]; // PY/PTOT | |
199 | } | |
200 | ||
201 | //__________________________________________________________________________ | |
202 | void AliMUONTrackParam::GetFromGeant3Parameters(Double_t *VGeant3, Double_t Charge) | |
203 | { | |
204 | // Get track parameters in current AliMUONTrackParam | |
956019b6 | 205 | // from Geant3 parameters pointed to by "VGeant3", |
206 | // assumed to be calculated for forward motion in Z. | |
a9e2aefa | 207 | // "InverseBendingMomentum" is signed with "Charge". |
208 | this->fNonBendingCoor = VGeant3[0]; // X | |
209 | this->fBendingCoor = VGeant3[1]; // Y | |
210 | this->fZ = VGeant3[2]; // Z | |
211 | Double_t pYZ = VGeant3[6] * TMath::Sqrt(1.0 - VGeant3[3] * VGeant3[3]); | |
212 | this->fInverseBendingMomentum = Charge / pYZ; | |
213 | this->fBendingSlope = VGeant3[4] / VGeant3[5]; | |
214 | this->fNonBendingSlope = VGeant3[3] / VGeant3[5]; | |
215 | } | |
216 | ||
217 | //__________________________________________________________________________ | |
218 | void AliMUONTrackParam::ExtrapToStation(Int_t Station, AliMUONTrackParam *TrackParam) | |
219 | { | |
220 | // Track parameters extrapolated from current track parameters ("this") | |
221 | // to both chambers of the station(0..) "Station" | |
222 | // are returned in the array (dimension 2) of track parameters | |
223 | // pointed to by "TrackParam" (index 0 and 1 for first and second chambers). | |
224 | Double_t extZ[2], z1, z2; | |
ecfa008b | 225 | Int_t i1 = -1, i2 = -1; // = -1 to avoid compilation warnings |
a9e2aefa | 226 | AliMUON *pMUON = (AliMUON*) gAlice->GetModule("MUON"); // necessary ???? |
227 | // range of Station to be checked ???? | |
228 | z1 = (&(pMUON->Chamber(2 * Station)))->Z(); // Z of first chamber | |
229 | z2 = (&(pMUON->Chamber(2 * Station + 1)))->Z(); // Z of second chamber | |
230 | // First and second Z to extrapolate at | |
231 | if ((z1 > this->fZ) && (z2 > this->fZ)) {i1 = 0; i2 = 1;} | |
232 | else if ((z1 < this->fZ) && (z2 < this->fZ)) {i1 = 1; i2 = 0;} | |
233 | else { | |
234 | cout << "ERROR in AliMUONTrackParam::CreateExtrapSegmentInStation" << endl; | |
235 | cout << "Starting Z (" << this->fZ << ") in between z1 (" << z1 << | |
236 | ") and z2 (" << z2 << ") of station(0..) " << Station << endl; | |
237 | } | |
238 | extZ[i1] = z1; | |
239 | extZ[i2] = z2; | |
240 | // copy of track parameters | |
241 | TrackParam[i1] = *this; | |
242 | // first extrapolation | |
243 | (&(TrackParam[i1]))->ExtrapToZ(extZ[0]); | |
244 | TrackParam[i2] = TrackParam[i1]; | |
245 | // second extrapolation | |
246 | (&(TrackParam[i2]))->ExtrapToZ(extZ[1]); | |
247 | return; | |
248 | } | |
249 | ||
04b5ea16 | 250 | //__________________________________________________________________________ |
251 | void AliMUONTrackParam::ExtrapToVertex() | |
252 | { | |
253 | // Extrapolation to the vertex. | |
254 | // Returns the track parameters resulting from the extrapolation, | |
255 | // in the current TrackParam. | |
956019b6 | 256 | // Changes parameters according to Branson correction through the absorber |
04b5ea16 | 257 | |
5b64e914 | 258 | Double_t zAbsorber = -503.0; // to be coherent with the Geant absorber geometry !!!! |
259 | // spectro. (z<0) | |
04b5ea16 | 260 | // Extrapolates track parameters upstream to the "Z" end of the front absorber |
b45fd22b | 261 | ExtrapToZ(zAbsorber); // !!! |
5b64e914 | 262 | // Makes Branson correction (multiple scattering + energy loss) |
04b5ea16 | 263 | BransonCorrection(); |
5b64e914 | 264 | // Makes a simple magnetic field correction through the absorber |
b45fd22b | 265 | FieldCorrection(zAbsorber); |
04b5ea16 | 266 | } |
267 | ||
43af2cb6 | 268 | |
269 | // Keep this version for future developments | |
04b5ea16 | 270 | //__________________________________________________________________________ |
43af2cb6 | 271 | // void AliMUONTrackParam::BransonCorrection() |
272 | // { | |
273 | // // Branson correction of track parameters | |
274 | // // the entry parameters have to be calculated at the end of the absorber | |
275 | // Double_t zEndAbsorber, zBP, xBP, yBP; | |
276 | // Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta; | |
277 | // Int_t sign; | |
278 | // // Would it be possible to calculate all that from Geant configuration ???? | |
279 | // // and to get the Branson parameters from a function in ABSO module ???? | |
280 | // // with an eventual contribution from other detectors like START ???? | |
281 | // // Radiation lengths outer part theta > 3 degres | |
282 | // static Double_t x01[9] = { 18.8, // C (cm) | |
283 | // 10.397, // Concrete (cm) | |
284 | // 0.56, // Plomb (cm) | |
285 | // 47.26, // Polyethylene (cm) | |
286 | // 0.56, // Plomb (cm) | |
287 | // 47.26, // Polyethylene (cm) | |
288 | // 0.56, // Plomb (cm) | |
289 | // 47.26, // Polyethylene (cm) | |
290 | // 0.56 }; // Plomb (cm) | |
291 | // // inner part theta < 3 degres | |
292 | // static Double_t x02[3] = { 18.8, // C (cm) | |
293 | // 10.397, // Concrete (cm) | |
294 | // 0.35 }; // W (cm) | |
295 | // // z positions of the materials inside the absober outer part theta > 3 degres | |
296 | // static Double_t z1[10] = { 90, 315, 467, 472, 477, 482, 487, 492, 497, 502 }; | |
297 | // // inner part theta < 3 degres | |
298 | // static Double_t z2[4] = { 90, 315, 467, 503 }; | |
299 | // static Bool_t first = kTRUE; | |
300 | // static Double_t zBP1, zBP2, rLimit; | |
301 | // // Calculates z positions of the Branson's planes: zBP1 for outer part and zBP2 for inner part (only at the first call) | |
302 | // if (first) { | |
303 | // first = kFALSE; | |
304 | // Double_t aNBP = 0.0; | |
305 | // Double_t aDBP = 0.0; | |
306 | // Int_t iBound; | |
307 | ||
308 | // for (iBound = 0; iBound < 9; iBound++) { | |
309 | // aNBP = aNBP + | |
310 | // (z1[iBound+1] * z1[iBound+1] * z1[iBound+1] - | |
311 | // z1[iBound] * z1[iBound] * z1[iBound] ) / x01[iBound]; | |
312 | // aDBP = aDBP + | |
313 | // (z1[iBound+1] * z1[iBound+1] - z1[iBound] * z1[iBound] ) / x01[iBound]; | |
314 | // } | |
315 | // zBP1 = (2.0 * aNBP) / (3.0 * aDBP); | |
316 | // aNBP = 0.0; | |
317 | // aDBP = 0.0; | |
318 | // for (iBound = 0; iBound < 3; iBound++) { | |
319 | // aNBP = aNBP + | |
320 | // (z2[iBound+1] * z2[iBound+1] * z2[iBound+1] - | |
321 | // z2[iBound] * z2[iBound ] * z2[iBound] ) / x02[iBound]; | |
322 | // aDBP = aDBP + | |
323 | // (z2[iBound+1] * z2[iBound+1] - z2[iBound] * z2[iBound]) / x02[iBound]; | |
324 | // } | |
325 | // zBP2 = (2.0 * aNBP) / (3.0 * aDBP); | |
326 | // rLimit = z2[3] * TMath::Tan(3.0 * (TMath::Pi()) / 180.); | |
327 | // } | |
328 | ||
329 | // pYZ = TMath::Abs(1.0 / fInverseBendingMomentum); | |
330 | // sign = 1; | |
331 | // if (fInverseBendingMomentum < 0) sign = -1; | |
332 | // pZ = pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); | |
333 | // pX = pZ * fNonBendingSlope; | |
334 | // pY = pZ * fBendingSlope; | |
335 | // pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX); | |
336 | // xEndAbsorber = fNonBendingCoor; | |
337 | // yEndAbsorber = fBendingCoor; | |
338 | // radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber; | |
339 | ||
340 | // if (radiusEndAbsorber2 > rLimit*rLimit) { | |
341 | // zEndAbsorber = z1[9]; | |
342 | // zBP = zBP1; | |
343 | // } else { | |
344 | // zEndAbsorber = z2[3]; | |
345 | // zBP = zBP2; | |
346 | // } | |
347 | ||
348 | // xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP); | |
349 | // yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP); | |
350 | ||
351 | // // new parameters after Branson and energy loss corrections | |
352 | // pZ = pTotal * zBP / TMath::Sqrt(xBP * xBP + yBP * yBP + zBP * zBP); | |
353 | // pX = pZ * xBP / zBP; | |
354 | // pY = pZ * yBP / zBP; | |
355 | // fBendingSlope = pY / pZ; | |
356 | // fNonBendingSlope = pX / pZ; | |
357 | ||
358 | // pT = TMath::Sqrt(pX * pX + pY * pY); | |
359 | // theta = TMath::ATan2(pT, pZ); | |
360 | // pTotal = | |
361 | // TotalMomentumEnergyLoss(rLimit, pTotal, theta, xEndAbsorber, yEndAbsorber); | |
362 | ||
363 | // fInverseBendingMomentum = (sign / pTotal) * | |
364 | // TMath::Sqrt(1.0 + | |
365 | // fBendingSlope * fBendingSlope + | |
366 | // fNonBendingSlope * fNonBendingSlope) / | |
367 | // TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope); | |
368 | ||
369 | // // vertex position at (0,0,0) | |
370 | // // should be taken from vertex measurement ??? | |
371 | // fBendingCoor = 0.0; | |
372 | // fNonBendingCoor = 0; | |
373 | // fZ= 0; | |
374 | // } | |
375 | ||
04b5ea16 | 376 | void AliMUONTrackParam::BransonCorrection() |
377 | { | |
378 | // Branson correction of track parameters | |
379 | // the entry parameters have to be calculated at the end of the absorber | |
43af2cb6 | 380 | // simplified version: the z positions of Branson's planes are no longer calculated |
381 | // but are given as inputs. One can use the macros MUONTestAbso.C and DrawTestAbso.C | |
382 | // to test this correction. | |
04b5ea16 | 383 | // Would it be possible to calculate all that from Geant configuration ???? |
956019b6 | 384 | // and to get the Branson parameters from a function in ABSO module ???? |
385 | // with an eventual contribution from other detectors like START ???? | |
43af2cb6 | 386 | Double_t zBP, xBP, yBP; |
387 | Double_t pYZ, pX, pY, pZ, pTotal, xEndAbsorber, yEndAbsorber, radiusEndAbsorber2, pT, theta; | |
388 | Int_t sign; | |
04b5ea16 | 389 | static Bool_t first = kTRUE; |
b45fd22b | 390 | static Double_t zBP1, zBP2, rLimit, thetaLimit, zEndAbsorber; |
43af2cb6 | 391 | // zBP1 for outer part and zBP2 for inner part (only at the first call) |
04b5ea16 | 392 | if (first) { |
393 | first = kFALSE; | |
43af2cb6 | 394 | |
5b64e914 | 395 | zEndAbsorber = -503; // spectro (z<0) |
b45fd22b | 396 | thetaLimit = 3.0 * (TMath::Pi()) / 180.; |
5b64e914 | 397 | rLimit = TMath::Abs(zEndAbsorber) * TMath::Tan(thetaLimit); |
398 | zBP1 = -450; // values close to those calculated with EvalAbso.C | |
399 | zBP2 = -480; | |
04b5ea16 | 400 | } |
401 | ||
402 | pYZ = TMath::Abs(1.0 / fInverseBendingMomentum); | |
403 | sign = 1; | |
404 | if (fInverseBendingMomentum < 0) sign = -1; | |
5b64e914 | 405 | pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro (z<0) |
04b5ea16 | 406 | pX = pZ * fNonBendingSlope; |
407 | pY = pZ * fBendingSlope; | |
408 | pTotal = TMath::Sqrt(pYZ *pYZ + pX * pX); | |
409 | xEndAbsorber = fNonBendingCoor; | |
410 | yEndAbsorber = fBendingCoor; | |
411 | radiusEndAbsorber2 = xEndAbsorber * xEndAbsorber + yEndAbsorber * yEndAbsorber; | |
412 | ||
413 | if (radiusEndAbsorber2 > rLimit*rLimit) { | |
04b5ea16 | 414 | zBP = zBP1; |
415 | } else { | |
04b5ea16 | 416 | zBP = zBP2; |
417 | } | |
418 | ||
419 | xBP = xEndAbsorber - (pX / pZ) * (zEndAbsorber - zBP); | |
420 | yBP = yEndAbsorber - (pY / pZ) * (zEndAbsorber - zBP); | |
421 | ||
422 | // new parameters after Branson and energy loss corrections | |
b45fd22b | 423 | // Float_t zSmear = zBP - gRandom->Gaus(0.,2.); // !!! possible smearing of Z vertex position |
424 | Float_t zSmear = zBP; | |
425 | ||
426 | pZ = pTotal * zSmear / TMath::Sqrt(xBP * xBP + yBP * yBP + zSmear * zSmear); | |
427 | pX = pZ * xBP / zSmear; | |
428 | pY = pZ * yBP / zSmear; | |
04b5ea16 | 429 | fBendingSlope = pY / pZ; |
430 | fNonBendingSlope = pX / pZ; | |
5b64e914 | 431 | |
04b5ea16 | 432 | |
433 | pT = TMath::Sqrt(pX * pX + pY * pY); | |
5b64e914 | 434 | theta = TMath::ATan2(pT, TMath::Abs(pZ)); |
b45fd22b | 435 | pTotal = TotalMomentumEnergyLoss(thetaLimit, pTotal, theta); |
04b5ea16 | 436 | |
437 | fInverseBendingMomentum = (sign / pTotal) * | |
438 | TMath::Sqrt(1.0 + | |
439 | fBendingSlope * fBendingSlope + | |
440 | fNonBendingSlope * fNonBendingSlope) / | |
441 | TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope); | |
442 | ||
443 | // vertex position at (0,0,0) | |
444 | // should be taken from vertex measurement ??? | |
445 | fBendingCoor = 0.0; | |
446 | fNonBendingCoor = 0; | |
447 | fZ= 0; | |
448 | } | |
b45fd22b | 449 | |
04b5ea16 | 450 | //__________________________________________________________________________ |
b45fd22b | 451 | Double_t AliMUONTrackParam::TotalMomentumEnergyLoss(Double_t thetaLimit, Double_t pTotal, Double_t theta) |
04b5ea16 | 452 | { |
453 | // Returns the total momentum corrected from energy loss in the front absorber | |
43af2cb6 | 454 | // One can use the macros MUONTestAbso.C and DrawTestAbso.C |
455 | // to test this correction. | |
b45fd22b | 456 | // Momentum energy loss behaviour evaluated with the simulation of single muons (april 2002) |
04b5ea16 | 457 | Double_t deltaP, pTotalCorrected; |
458 | ||
b45fd22b | 459 | // Parametrization to be redone according to change of absorber material ???? |
956019b6 | 460 | // See remark in function BransonCorrection !!!! |
04b5ea16 | 461 | // The name is not so good, and there are many arguments !!!! |
b45fd22b | 462 | if (theta < thetaLimit ) { |
463 | if (pTotal < 20) { | |
464 | deltaP = 2.5938 + 0.0570 * pTotal - 0.001151 * pTotal * pTotal; | |
04b5ea16 | 465 | } else { |
b45fd22b | 466 | deltaP = 3.0714 + 0.011767 *pTotal; |
04b5ea16 | 467 | } |
468 | } else { | |
b45fd22b | 469 | if (pTotal < 20) { |
470 | deltaP = 2.1207 + 0.05478 * pTotal - 0.00145079 * pTotal * pTotal; | |
04b5ea16 | 471 | } else { |
b45fd22b | 472 | deltaP = 2.6069 + 0.0051705 * pTotal; |
04b5ea16 | 473 | } |
474 | } | |
475 | pTotalCorrected = pTotal + deltaP / TMath::Cos(theta); | |
476 | return pTotalCorrected; | |
477 | } | |
478 | ||
b45fd22b | 479 | //__________________________________________________________________________ |
480 | void AliMUONTrackParam::FieldCorrection(Double_t Z) | |
481 | { | |
482 | // | |
483 | // Correction of the effect of the magnetic field in the absorber | |
484 | // Assume a constant field along Z axis. | |
485 | ||
486 | Float_t b[3],x[3]; | |
487 | Double_t bZ; | |
488 | Double_t pYZ,pX,pY,pZ,pT; | |
489 | Double_t pXNew,pYNew; | |
490 | Double_t c; | |
491 | ||
492 | pYZ = TMath::Abs(1.0 / fInverseBendingMomentum); | |
493 | c = TMath::Sign(1.0,fInverseBendingMomentum); // particle charge | |
494 | ||
5b64e914 | 495 | pZ = -pYZ / (TMath::Sqrt(1.0 + fBendingSlope * fBendingSlope)); // spectro. (z<0) |
b45fd22b | 496 | pX = pZ * fNonBendingSlope; |
497 | pY = pZ * fBendingSlope; | |
498 | pT = TMath::Sqrt(pX*pX+pY*pY); | |
499 | ||
5b64e914 | 500 | if (TMath::Abs(pZ) <= 0) return; |
b45fd22b | 501 | x[2] = Z/2; |
502 | x[0] = x[2]*fNonBendingSlope; | |
503 | x[1] = x[2]*fBendingSlope; | |
504 | ||
505 | // Take magn. field value at position x. | |
506 | gAlice->Field()->Field(x, b); | |
507 | bZ = b[2]; | |
508 | ||
509 | // Transverse momentum rotation | |
510 | // Parameterized with the study of DeltaPhi = phiReco - phiGen as a function of pZ. | |
5b64e914 | 511 | Double_t phiShift = c*0.436*0.0003*bZ*Z/pZ; |
b45fd22b | 512 | // Rotate momentum around Z axis. |
513 | pXNew = pX*TMath::Cos(phiShift) - pY*TMath::Sin(phiShift); | |
514 | pYNew = pX*TMath::Sin(phiShift) + pY*TMath::Cos(phiShift); | |
515 | ||
516 | fBendingSlope = pYNew / pZ; | |
517 | fNonBendingSlope = pXNew / pZ; | |
518 | ||
519 | fInverseBendingMomentum = c / TMath::Sqrt(pYNew*pYNew+pZ*pZ); | |
520 | ||
521 | } |