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